what brake pedal travel

HOW TO FIX EXCESSIVE BRAKE PEDAL TRAVEL

What Is Excessive Brake Pedal Travel?

Excessive brake pedal travel happens when you feel your pedal sinking rapidly while braking, or sitting lower than usual when activating your vehicle’s brakes. This can happen due to wobbly discs knocking pistons back or air in the braking system.

Performing DIY brake repair to fix excessive brake pedal travel can be a tedious task. Follow the steps below to diagnose and repair your sinking brakes.

How to Fix Excessive Brake Pedal Travel

1. Diagnose the Problem . To diagnose issues with the master cylinder, the first thing you need to do is remove the lines, install brass or plastic plugs into the outlets, and apply the brakes. What happens when you apply the brakes will tell you what issue your vehicle is having. You can continue this process of elimination by isolating each wheel.

2. Use Your Parking Brake. If you don’t typically engage your parking brake, the parking brake can be key in figuring out if your car is suffering from excessive brake pedal travel. If the parking brake doesn’t properly engage, that generally means a low pedal.

3. Bleed the Brakes. Bleeding your brakes is an important step in brake pedal travel repair and other brake issues. Use a jelly jar half full of brake fluid and a short hose to depress your brake pedal.

While depressing the pedal, rotate the star wheel to lose up the clearance. Then, go back one click when the wheel scrapes. It’s best to have a partner on hand when bleeding your brakes.

4. Bleed the Master Cylinders . After bleeding the brakes, bleeding the master cylinders is the next step. In traditional systems, you begin with the longest line in the circuit first, and go from the right rear, left rear, right front, and left the front. In diagonally split systems, the order is right rear, left front, left rear, and right front. Flush out the bleeder valves, and finally, remove the air from your master cylinder.

If you’re not sure which type of system your vehicle is or are unaware of the proper tools needed to fix excessive brake pedal travel, it’s best to bring your vehicle into Brake Works.

With two convenient locations with great weekend hours, getting proper brake maintenance is simpler than you think. Contact our team of certified specialists to schedule an appointment.

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Dealing With A Low Brake Pedal

"Honey, can I borrow your car?" No problem. She tosses you the keys. But at the first stop sign you draw a startled breath--the pedal's going, going, almost gone! There's even a little dent in the carpet under the pedal. Didn't she notice? Well, no she didn't. Typically, low-pedal trouble develops so gradually that people don't realize it.

Hydraulic brakes have been around since Duesenberg introduced them in 1921, but apparently a long history is no defense against troubles. And professionals and do-it-yourselfers alike are often guilty of misdiagnosis--they blame the master cylinder, though it is seldom the culprit.

There are only two plausible reasons for a low pedal: air in the system; and excessive movement between linings and rotors or drums (due to lack of adjustment, an out-of-round drum, or a wobbly disc that's knocking the pistons back so that there's extra space to take up before braking action begins).

Isolation You can find out all you need to know about the master cylinder by removing the lines, screwing brass or plastic plugs into the outlets, and then applying the brakes. If the pedal's high and hard now, the master has been properly bled and its seals are okay. The pedal would sink gradually if it were bypassing--that is, if fluid were finding its way around the sliding seals. You've also confirmed that the booster is okay. Reattach the lines.

Continue the process of elimination by clamping hoses to isolate each wheel. Use a suitable rounded-jaw tool, either the locking-pliers type or one of those inexpensive J-hooks with a knurled screw. Releasing one at a time should locate the problem.

Use That Parking Brake If you never engage the parking brake, self-adjustment of the pads and rotor simply won't occur, and that means a low pedal. Another impediment to adjustment is corrosion and contamination of the piston, cylinder and self-adjustment hardware. So, change your habits and start using the parking brake every time you leave the car, and overhaul or replace those calipers if they're not just right. If the parking brake isn't used regularly, one of these days a parking lot attendant will apply it and your car will be immobilized until those corroded cables and other seized parts are replaced.

Beat The Drums Rear drum brakes can cause a low pedal, too. Seized star-wheel screws and otherwise inoperative self-adjusters are practically an epidemic, and you're risking trouble if you don't replace the hardware when replacing shoes. At the very least, clean the star-wheel threads and treat them to a coating of antiseize compound.

There's another factor that's usually not recognized: drivers who never stop aggressively enough in Reverse to ratchet the self-adjusters. It's a good idea to stomp on the brake pedal every week or so while backing up--preferably in a deserted lot or other safe place.

What about the drums themselves? They're frequently out of round, leaving excess shoe-to-drum clearance and, of course, causing pulsation.

The old-fashioned, low-tech way to bleed brakes is to use a jelly jar half full of brake fluid, a short piece of hose, and a patient helper to depress the brake pedal.

Depress the tab while you rotate the star wheel to close up the clearance. When the wheel scrapes lightly, go back one click.

Brake drums will be marked clearly as to how far they can be machined safely to remove out of round.

Bubble Trouble For all practical purposes, brake fluid is incompressible. Air, on the other hand, can be squeezed down into a smaller-than-natural volume, and its presence will disrupt the operation of any hydraulic system. It promotes internal corrosion, too. Ergo, it must be expelled.

The most common cause of pedal problems is failure to bench bleed a new master cylinder. Screw the supplied fittings into the outlets and place the tips of the tubes in the fluid in the reservoir. Clamp one of the master's mounting ears in a vise--don't grip around the cylinder--so the unit is as level as possible. Use a rod or drift to stroke the piston slowly. Wait at least 15 seconds between strokes to allow the low-pressure chamber to release all its bubbles and fill completely. Keep stroking until there's no more evidence of air at the ports and tube tips.

If the car has a replacement cylinder that somebody didn't bench bleed, you might be able to do it with the master in place, provided you can jack the rear of the vehicle high enough to get the cylinder to be level. Again, pump slowly and allow time between strokes.

An important precaution to observe during any bleeding procedure that involves pumping the pedal is to limit pedal travel. You don't want the delicate lips of the master cylinder's piston seals to ride so deep in the bore that they encounter rough corrosion or deposits, which can scratch them. Just throw a chunk of 2 x 4 on the floor under the pedal.

When it comes to the bleeders at the wheels, most people just open them and let the fluid squirt. Not only will this result in slippery puddles on the floor, the fluid can shoot farther than you might expect--think about the 2500-plus psi of line pressure on some ABS-equipped cars. Brake fluid is a pretty effective paint remover, and it really burns when you get it in your eye. Wear eye protection.

One convenient setup is a tube and transparent bottle kept half full of fresh fluid. There are also inexpensive 1-man bleeder hoses that contain a 1-way valve to eliminate the possibility of air being drawn back in when you release the pedal.

The bleeder cups and hoses that are often included in manual vacuum pump kits, such as those from Mighty Vac, work well. Once again, you can see what you're getting, and you don't have to keep climbing into the seat to pump the pedal.

You should also be aware of special procedures. For example, on Teves Mark II ABS systems, you can't get fluid to the rear brakes unless you turn the key on and then apply the pedal slightly. Be sure to check the shop manual if your vehicle has an antilock braking system.

Finally, there's the bleeding sequence. Since you're supposed to do the longest line in the circuit first, the traditional order is right rear, left rear, right front and left front. But with the diagonally split systems you'll find mostly on fwd cars, the order is right rear, left front, left rear then right front. ABS-equipped cars may have special procedures to follow.

Bubbles collecting in high spots in the brake system need to be removed by opening the bleeder valves to flush them out.

Bench bleed a master cylinder to get air out before installing it into the vehicle.

How It Works: The Dual Master Cylinder

Whether you call it the dual, split or tandem master cylinder, it has been used on every car sold in this country since 1967, although Cadillac had it in '62. Even so, most people don't understand its construction and operation. A typical modern specimen is of the composite variety--aluminum with a plastic reservoir--but iron 1-piece units are still around on older vehicles. Two pistons ride in the bore, and here's where we encounter some potentially confusing terminology. The rear piston is the primary, the one in the front is the secondary. This apparent misnaming resulted because the rear piston is the first to receive the signal from the brake pedal, so it does make a certain amount of sense. Kind of. Each piston has a primary cup seal at its front and a secondary at its rear. In normal braking, the pushrod from the booster forces the primary piston forward. No pressure is created until the primary seal covers the compensating or vent port from the reservoir, but once it does fluid is trapped in the chamber between the pistons and it becomes a solid column. Pressure is routed from this chamber to two wheels. A combination of the trapped fluid and the primary piston coil spring bears on the secondary piston, to which the line to the other two wheels is attached. The replenishing ports allow fluid to move freely between the chambers behind both pistons' primary cups and the reservoir, determined by demand and expansion and contraction from temperature changes. If a hose lets go or a saboteur has sawed through one of the brake lines, the other half will still provide a means of decelerating the vehicle, albeit with a lower pedal and reduced stopping power. This protective function is, of course, the dual master's reason for being.

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June 2019 Issue

Abnormal brake pedal diagnosis.

By Roy Dennis Ripple

A customer may complain of a brake pedal that ‘feels funny.’ It's your job to determine whether it’s due to aerated and/or contaminated brake fluid, excessive pedal travel or any other cause.

Vehicles normally respond to our commands in a fairly predictable manner. When we push on the accelerator, we go forward; when we turn the steering wheel, we change direction; and when we press the brake pedal, we stop. Of all the things we ask of our vehicles, “please stop” is the most important request. The brake pedal should give the driver a reassuring feel that says, “I got this.”

The brake pedal is the driver’s physical connection to the brake system, providing feedback that the driver uses to determine if there’s a problem with his brakes. Spongy, mushy and squishy are just a few of the terms that a customer might use to describe negative brake pedal feedback. Sometimes these concerns can be tricky to diagnose due to the numerous failures that can cause an unacceptable brake pedal feel.

The first step in diagnosing a low brake pedal concern is to determine the type of low brake pedal issue you’re dealing with, and if other symptoms are present. It might be a good idea to forgo the road if you’re uncomfortable with the function of the brakes and settle for a parking lot cruise instead.

Besides a low or mushy pedal, note if the brakes pull, squeak or pulsate. Does the pedal slowly drift to the floor when at a stop, or does it stop solid, but too close to the floor? Determine if one or more wheels are locking up, and note if the red or amber brake warning lamps are illuminated. All of this information will aid in your diagnosis.

A low brake pedal is always caused by either a hydraulic or a mechanical malfunction. When a mechanical malfunction is the cause, it’s due to a component moving past the range of motion for which it was designed. A good example of this is out-of-adjustment rear brake shoes. The universally accepted specification for brake shoe-to-drum clearance is .015 in. Every thousandth of an inch over spec causes excess brake pedal travel. Less than .025 in. travel at the master cylinder pushrod can equal about ½ in. at the pedal. Every little bit of unnecessary movement adds up.

Another example is a caliper piston that retracts too far into the bore when disengaged. Rear calipers with integral parking brakes are notorious for this. This causes the piston to travel further than designed to initiate contact between the inboard pad and the rotor. This excess travel can translate into a heap of movement at the brake pedal.

Hydraulic concerns present the biggest challenge in low brake pedal diagnosis. The smallest amount of air trapped anywhere in the system will have a big effect on brake pedal feel. Brake fluid converts the energy applied to the pedal into the force required to engage the brakes. This happens because fluids are compressible only to a very small degree, so any pressure applied to a liquid is transferred to all portions of the liquid and to the walls of the container it occupies. Since air is very compressible, air creates a nice, soft cushion for the fluid to lean on, ruining any chance of achieving solid hydraulic pressure.

Use the information you acquired during the road test to guide your initial visual inspection. Watch all the calipers move while an assistant pumps the brake pedal. Worn caliper pins or incorrectly installed brake pads can cause the caliper to flex side to side. This lateral movement uses up brake pedal travel. Be cautious of brake pads that are location-specific, or that need to line up with a locating pin during installation. If these pads are incorrectly installed, they’ll cause the caliper to flex.

While you’re eyeballing the calipers, make sure they’re on the correct side. When a caliper is installed on the wrong side, the bleeder valve will be below the inlet. Since air rises to the top, good luck bleeding that caliper. Check meticulously for an external leak. Brake fluid leaks don’t always present themselves as drops that puddle in the driveway. Just a little seepage at a fitting can cause big trouble at the pedal. Don’t forget to look behind the wheel cylinder boots while checking for leaks; there should be no fluid there.

During your visual inspection, also watch the rubber hoses as a helper pumps the brake pedal. Look for a bulge in the hose that appears under pressure, then disappears when the pedal is released. I’ve seen hoses twist while pressurized due to a defect at the union where the rubber hose meets the metal crimp. Excess hose movement causes excess pedal movement.

Most negative brake pedal feedback issues fall into one or more of the following categories:

•A pedal that stops hard at the bottom but has excess play at the top is usually the result of a master cylinder or pushrod issue. •A pedal that’s spongy or mushy can be caused by air intrusion, contaminated brake fluid or a mechanical component moving beyond its designed range of motion. •A pedal that continues to move toward the floor when applied is caused by a loss of hydraulic pressure, which can be caused by an external leak or an internally leaking component. Contaminated brake fluid can also cause a brake pedal to drift downward.

An occasional exception to these rules—there’s always an exception—is the antilock brake system (ABS) hydraulic control unit (HCU). A defective HCU will create symptoms that feel like air intrusion or a pressure loss and can really complicate your diagnosis.

Let’s look at a brake pedal that stops hard at the bottom but has excess play at the top. A good way to determine if there’s too much pushrod travel is to loosen the master cylinder-to-power booster attaching hardware. Have an assistant hold the loose master cylinder firmly against the booster while you slowly apply the brake pedal. Determine how far the pedal moves before your helper feels the push on the master cylinder. Excessive pushrod play could be caused by a weak or broken master cylinder bore spring that’s not returning the piston all the way to the back of the bore, or it could be a pushrod or booster issue. Remember, a little play at the pushrod is a lot at the pedal.

Many automakers use an adjustable pushrod. This adjustment is set at the factory and shouldn’t have to be messed with. If you need to adjust the pushrod, something’s wrong.

We once serviced a Ford Escape with excessive brake pedal travel at the top. Loosening the master cylinder determined that we lost about 3 in. of pedal travel before the piston moved. We removed the master cylinder and discovered that the small dome-shaped piece that was pressed into the end of the pushrod, which fits into the master cylinder bore, was missing, and laying at the bottom of the booster. This added almost ¼ in. of travel to the pushrod.

Diagnosing a spongy, mushy brake pedal issue can sometimes be frustrating as well as time-consuming. Here’s an example of how important the initial road test is when diagnosing a spongy brake pedal.

While we were road-testing a vehicle with a low, spongy brake pedal, we noticed that the brakes pulled to the left. That told us that the left front and right front calipers were not applying evenly. Using the results from the road test, we started our visual inspection at the front calipers. Both front wheels were spinning freely and both stopped spinning when the brakes were applied. There was no excessive movement in either caliper or hose during brake application, and the brake pads were a healthy 9mm, with nice, beefy rotors.

Since the road test suggested there was an issue with the front brakes, it only made sense to check the front calipers for air. We removed a nice pocket of air from the right front caliper, which temporarily fixed the pedal. I say “temporarily” because we found no reason for that caliper to be holding air, as there was no sign that it was recently disassembled. Caliper piston seals and wheel cylinder cup seals can replicate a one-way check valve. Fluid can’t get out but air can get in. So we replaced the caliper. This scenario reinforces the importance of gathering information during the road test. If we didn’t feel the brake pull, we wouldn’t have started our diagnosis at the front calipers.

Unfortunately, it’s not always that simple. If you’re faced with a low, mushy pedal and the visual inspection yields no clues, it’s time to break out the blockers. Blocking off sections of the brake system (not individual components) is the surest way to find the cause of the problem. Thexton Manufacturing makes a master cylinder plug kit (Part No. 803P) that can also be used on HCUs. It’s important to use quality plugs when blocking brake pressure. A small leak at a plug will yield erroneous results.

Always start by blocking the master cylinder ports. If the master cylinder is good, the pedal should be rock hard—barely moving—with the ports blocked. If the brake pedal moves at all, the master cylinder is leaking internally, there’s a pushrod issue or the brake fluid is contaminated.

If the master cylinder is good, most diagnostic procedures recommend blocking the HCU ports next. The problem is that the HCU tends to be hard to access, and the fittings are usually tough to get a wrench on due to their proximity to each other. So in the spirit of streamlined diagnosis, it makes sense to check the easier-to-access components first, which would be the wheels.

Block each wheel individually at the steel line, before the rubber hose; this way, you’re taking the hoses, calipers and wheel cylinders out of the equation. Do not block off the calipers by using vise grips to crimp the rubber hoses. Damaging a rubber brake hose could cause it to work like a one-way valve, allowing pressure to be applied to the caliper but not to bleed off, causing a perpetually applied brake caliper. The Thexton block-off kit contains only male fittings, and you need a female fitting to block the steel line. Attaching a brass union to the male plug works great. Test the pedal after blocking each wheel. We found a right rear caliper on a Ford Explorer that was causing a low, spongy pedal using this method. We never did identify the actual cause of the caliper malfunction. It wasn't leaking, the pins were sturdy, no air, all looked fine. But the pedal came right up when we blocked it off. We replaced it; problem fixed.

If you find no problem at the wheels, you’ll need to access the HCU. It’s best to block all the outlet ports on the HCU at the same time. This is a lot of work just for a diagnosis, but at this point there’s very little choice.

If the pedal is still low with all the HCU outlet ports blocked, before passing sentence on the HCU, perform a service bleed. HCUs seem to be a favorite resting place for stowaway air. Even if you have no reason to believe that the brake system was opened to atmosphere, you should bleed the HCU before condemning it.

ABS service bleed procedures are performed with a scan tool and vary by manufacturer. Some procedures are as easy as pressing the brake pedal a few times and clicking a button on the scan tool; others will require you to open bleeder valves, which makes a real mess on the shop floor. Whatever the procedure, it’s very important to bleed all the wheels after performing an ABS service bleed.

I started using a brake pressure bleeder a couple of years ago and I’ll never go back to the old pedal-pumping method. Pressure bleeders work great. They attach to the master cylinder reservoir in place of the cap and put the brake system under consistent pressure. The biggest advantage of this—besides not needing an assistant—is that you can open a bleeder valve and just let it flow, pushing all of the air out of a line from the master cylinder to the wheel cylinder or caliper with just one turn of a bleed er valve. If you don’t already have a pressure bleeder, I highly recommend getting one.

It’s important to properly benchbleed a new master cylinder before installation. It can be tough to bleed the air from a master cylinder once it’s installed on the vehicle. Mount the master cylinder firmly in a vise and screw bleeder fittings into the outlet ports. Attach hoses to the fittings, with the other ends of the hoses in the reservoir, submerged in brake fluid. An effective kit for bench-bleeding a master cylinder comes with check valves, which allow the air to be pushed out while not allowing air to get sucked in on the back stroke. Thexton, Dorman, NAPA and others offer such kits.

If you don’t have check valves for the hoses, the procedure will still work. Since the hoses are submerged in brake fluid, fluid from the reservoir rather than air will be pulled back into the master cylinder. The problem is that air that doesn’t make it to the end of the hose gets sucked back into the cylinder on the back stroke. Check valves prevent this from happening.

With the hoses in place, slowly push the piston into the master cylinder, then allow the piston to return to the rest position. You’ll see air bubbles exit the master cylinder through the clear hoses. Do not push the piston past its normal range of motion; doing so can damage the piston seals, rendering the master cylinder useless. When using check valves, all the air is gone within seven to ten strokes. Be sure that the fittings are tight, as a poor seal at a fitting will pull air into the master cylinder.

The heart of a hydraulic brake system is the fluid, and when that goes bad, so does the pedal. Most automotive applications use DOT 3, DOT 4 or DOT 5.1 fluid, all of which are glycol-ether-based. DOT 5 is silicone-based and should not be mixed with glycol-based brake fluids. The most important property of brake fluid is that it maintains a stable viscosity and compressibility throughout its entire operating temperature range—very cold to very hot. The negative property of brake fluid is that it’s hygroscopic, which means it absorbs water.

Water in brake fluid greatly lowers its boiling point. The dry boiling point of DOT 3 is 401ºF. The wet boiling point, defined by the temperature at which the fluid boils after absorbing 3.7% water by volume, is 285ºF. Big difference. Since brake fluid temperatures at the calipers can easily exceed 200ºF, this could be a problem. The fact that water freezes also tends to complicate things a bit. This is why it’s recommended that brake fluid be changed every two years.

When brake fluid is contaminated with water it turns a darker color. If the brake fluid looks contaminated, or if you’re diagnosing a vehicle that’s more than two years old, recommend a brake fluid flush. Use a pressure bleeder or brake fluid flush machine to push all the old fluid out through the bleeder valves. Be sure to check all the bleeder valves before selling the brake flush. If you think the valves are going to break off, you need to know this beforehand.

A couple of more things: A customer might describe an intermittent false ABS activation event as a low brake pedal. But if the pedal feels fine to you, check for DTCs in the ABS module. Also, contaminated fluid can damage an HCU. Brake fluid is designed to protect metal brake parts against corrosion, an attribute it loses when weakened by water. So when replacing an HCU, it’s imperative to flush the fluid.

It seems that the furthest thing from anyone’s mind as he’s driving down the road is the brake system. The song on the radio or the setting of the climate control system occupy more brain space than the brakes do. So maybe problems like a low brake pedal and/or noisy brakes should be looked upon as an important safety warning. It’s the brake system whispering, “Hey, remember me?” to the procrastinator who should plan on getting his brakes checked very soon.

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What is brake pedal ratio?

Pedal ratio is an important but often overlooked part of your braking system. It tells you how the force you apply to the pedal is multiplied and transferred to the Master Cylinder . It also affects how far the pedal travels.

Why is it important?

The average person can press on the brake pedal with about 70 lbs. of force. However, to stop a moving vehicle, disc brakes require 800-1,200 psi at the calipers. The force you put on the pedal is amplified by all the parts of the system. The pedal ratio is one thing that helps.

How is it calculated?

• This is measurement “A” in the diagram.
• This is measurement “B” in the diagram.
• “A” divided by “B” equals the pedal ratio.

For Example

Assume the following:

• Measurement “A” = 12 in.
• Measurement “B” = 3 in.

12 divided by 3 = 4. In this case, the pedal ratio is 4:1.

How does it affect performance?

Using the numbers from the examples above shows how the force is multiplied:

• 70 lbs. of force applied to the pedal
• A 4:1 pedal ratio
• Equals 280 lbs. of force applied to the master cylinder pushrod

For power brake systems, the Brake Booster increases the force even more. This makes stopping easier and driving more enjoyable.

Also, take note of the pedal travel:

• A master cylinder with a 1.10 in. stroke
• The pedal needs to travel 4.40 in.

It's important that the master cylinder bottoms out before the pedal hits the floor. This ensures the master cylinder moves enough fluid to stop the vehicle.

What should the pedal ratio be?

Pedal ratio is not something that is easily changed. However, it is something to consider during a custom build. It also comes into play when converting from manual to power brakes or vice versa.

The right pedal ratio depends on the brake system design. The pedal ratio needs to work with:

• Manual vs. Power Brakes
• Disc vs. Drum Brakes
• Master Cylinder Diameter
• Wheel Cylinder Diameter
• Caliper Piston Diameter

The chart below lists some basic guidelines. With some fabrication, your pedal ratio can be fine-tuned to meet your needs.

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Mailbag: How to Calculate Brake Pedal Ratio and Master Cylinder Size

Q:  I’m putting together a disc brake system for a custom build. What can you tell me about setting up brake pedal ratio for optimum performance? Also, what can you tell me about master cylinders ? Specifically, what do I need to know about the bore size of the master cylinder?

A properly engineered brake system should deliver sufficient fluid volume to produce a firm, responsive pedal while generating enough pressure to stop your vehicle comfortably. A typical disc brake system requires between 900 and 1,200 psi at the brake caliper (as measured with a pressure gauge). Most master cylinders have a bore size of 5/8-inch to 1 1/8-inch. Larger-bore master cylinders move a high volume of brake fluid, at lower pressure with less pedal travel. A smaller bore moves less fluid at higher pressure with increased pedal travel. If fluid pressure at the caliper measures low, reducing the master cylinder’s bore size will increase pressure and vice-versa.

This is another in a series of weekly Q&A Mailbag sessions with  Summit Racing ‘s tech department, in which there are hundreds more.  Click here to see them all . 

Dave Matthews was a mechanic for the U.S. Army, a Ford dealership, and served for many years as a fleet mechanic for construction companies. Now a technical content producer at Summit Racing, Dave has spent decades working on everything from military vehicles to high performance race machines.

6 responses to “Mailbag: How to Calculate Brake Pedal Ratio and Master Cylinder Size”

Could we get an article on finding the right tire pressure for custom cars? Obivously adding or removing weight will effect optimum pressure. But does changing tire size?

[…] may help: Monday Mailbag: How to Calculate Brake Pedal Ratio and Master Cylinder Size – OnAllCylinders 8 to 1 is an aggressive ratio, "should" be more in the 5-7 to 1 ratio. You may have a […]

[…] Learn how to calculate the brake pedal ratio […]

What happens if the pedal ratio is way above 7:1 ratio for eg 10:1, what happens in this case…..

The higher pedal ratio will require more pedal travel to complete the proper stroke of the master cylinder (vs. a lower ratio like 6.1:1). It will also make it easier to push the pedal and stop the vehicle because the higher ratio will give you more leverage.

The downside of having too high of a pedal ratio is braking can get to a point where its too much travel and leverage for the system to operate with the correct “feel” and function, in your case it could lead to being too sensitive.

On a manual brake system sometimes a higher ratio can be beneficial, as long as pedal travel isn’t excessive, or the pedal travels all the way to the floor (or close too it) before the vehicle comes to a stop, you need to leave room for brake wear and a margin of error in the brake system.

There is a balance to find, and 5.1 to 7.1:1 is the industry standard, and yes there are exceptions to this.

Another thing to consider is how the master cylinder bore size will play a role in this, The larger the bore the less leverage (and travel) you have and vice-versa. Larger bores move more fluid with the same amount of travel than smaller bores do.

If you have a brake pedal with a low amount of travel that’s very firm, I would suggest reducing the bore size, this applies in the other direction as well, a pedal that travels too far and too sensitive should increase bore size.

Hope this helps.

[…] with pedal ratios are more common in older muscle cars than in more modern designs, but it does still crop up […]

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• Advice & How-To's

Why is My Brake Pedal Hard to Push?

A firm push on the brake pedal should pull you to a comfortable stop. However, when that pedal resists, it’s more than just an inconvenience – it’s a potential hazard. Regardless of what the cause might be, you need to get it corrected quickly so you can drive safely once again.

Before it can be repaired, you need to get to the bottom of the problem. Learn what conditions could make the brake pedal hard, how to troubleshoot it, and things you can do to solve it.

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Introduction to Brake Pedal Resistance

Initially, a stiff pedal might be dismissed as an occasional quirk, but when it happens often, it indicates an underlying issue with your vehicle’s hydraulic systems. It’s a signal that your vehicle’s most important safety feature has something wrong. Before you can fix the issue, understanding the symptoms and potential root causes is crucial.

Your vehicle’s brakes are designed to convert the kinetic energy of its moving wheels into heat energy, safely slowing the vehicle’s forward motion through controlled friction. The brake pedal is your direct line of communication with this process, exerting force through a system of mechanical and hydraulic functions. Travel should always be smooth and consistent, and when it isn’t, it indicates that there’s a problem.

Common Causes of a Hard Brake Pedal

A hard brake pedal can be as varied in its causes as the potential results of not addressing it. Four of the main culprits are:

• Hydraulic issues – Your vehicle’s brakes are part of a hydraulic system that multiplies force, allowing you to stop a heavy car with minimal effort. A stiff pedal can be a sign of pressure restriction within this system, possibly due to a kinked line, a bad proportioning valve , or even a damaged brake master cylinder.
• Brake booster problems – The brake booster amplifies the force applied to the brake pedal, making braking easier. If the brake booster develops a vacuum leak, which it uses to operate, the result is often a hard brake pedal.
• Vacuum leaks – Many modern brake systems rely on engines to create the vacuum necessary for brake boosters to function. A leak in the vacuum line or the booster diaphragm can occur, causing the system to lose vacuum pressure and the brake pedal to become stiff.
• Brake fluid contamination – Brake fluid is used to operate the hydraulic portion of your braking system. Over time, moisture can be absorbed into the brake fluid, lowering its boiling point, and potentially leading to a vapor lock that causes brake pedal stiffness.

Diagnosing Brake Pedal Issues

Before rolling up your sleeves, it’s important to diagnose the exact nature of your brake pedal issue.

Step 1: Check the Brake Fluid Level

Low brake fluid is an easy-to-spot cause for a stiff pedal. Ensuring the reservoir is properly filled can sometimes be the only fix needed. Always use the correct type of fluid for your vehicle from a new, sealed container.

Step 2: Feel the Brake Pedal During Operation

Is the pedal consistently hard, or does its resistance vary with vehicle speed or other conditions? Consistency points to hydraulic or fluid issues, while changes can indicate a booster or vacuum problem.

Step 3: Listen for Hissing Sounds

With the engine off, pump the brake pedal several times to deplete the booster’s vacuum reserve. If you hear hissing, you may have a vacuum leak.

Step 4: Perform a Visual Inspection

Inspect the brake lines and hoses for damage, as well as the vacuum lines leading to the brake booster. Some issues like cracking or rubs can point you toward the necessary repair.

DIY Solutions for a Stiff Brake Pedal

Tackling a stiff brake pedal can be a do-it-yourself project for many car owners. Here are some practical solutions to try.

Bleeding the Brake System

Air bubbles in the brake lines that can compress and lead to a spongy pedal feel can often be repaired by bleeding the brakes. This flushes out these bubbles, restoring hydraulic function and dependability.

Replacing Brake Booster

If you’ve verified a vacuum leak is causing your brake stiffness, you may need to replace the brake booster. This involves disconnecting the master cylinder and vacuum lines, installing the new booster, and ensuring a tight seal at each connection.

Fixing Vacuum Leaks

Locating the source of a vacuum leak can be challenging as many lines and fittings are tucked out of sight. Common culprits include deteriorated hoses, loose fittings, and failed gaskets. Once you find the problem, it’s often a quick fix of replacement or resealing.

Flush the Brake Fluid

A color change in your brake fluid to murky and brown is a sign of contamination and should be flushed out. Flushing involves removing all the old brake fluid and replacing it , ensuring your system’s fluid is clean, effective, and protecting you’re the inside against corrosion.

When to Seek Professional Help

If you’re running into a wall with your troubleshooting or want the assurance of a pro’s take on the situation, you might want to take it to a trusted garage. Check out one of our Preferred Shops to help you do the job.They can include unusual noises, spotty brake performance, or a pedal that intermittently hardens and softens should prompt an immediate visit to a certified mechanic.

Regular check-ups for your vehicle’s braking system are as essential for safety as they are for peace of mind. At AutoZone , you’ll find new brake fluid, brake repair parts, and any tools and equipment you might need to service and repair your car.

FAQ/People Also Ask

It may indicate potential issues such as hydraulic system problems, brake booster malfunctions, vacuum leaks, or brake fluid contamination.

Yes, low brake fluid can cause a stiff brake pedal as it means there’s less fluid available to apply the brakes. Check the fluid level, quality, and condition to rule out fluid as the cause of stiffness.

A stiff brake pedal can range from a common maintenance item like low brake fluid to more serious issues, such as brake system failure.

Brake fluid flushing and bleeding is typically recommended every two years to remove air from the lines and ensure proper brake function.

The brake booster multiplies the force applied to the brake pedal, allowing the driver to stop the vehicle with minimal effort.

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How Car Brakes Work and How to Tell When They Go Bad

B rakes are your vehicle's most important safety system. Under normal conditions, a driver exerts about 70 pounds of force on the brake pedal (about the same amount of effort it takes to bite into a steak) to bring thousands of pounds of moving metal and plastic to a quick and controlled stop. A flawless brake system is absolutely crucial to driver, passenger and pedestrian safety.

Read on to learn how a modern automotive brake system works and some of the most common brake system problems .

What Are the Different Types of Car Brakes?

• All modern vehicles come with hydraulic brakes. Hydraulic brake systems pressurize and transfer brake fluid to the wheel brakes assemblies. The brake assemblies (disc or drum) use the pressurized fluid to apply the brake friction material that generates the friction needed for braking.
• Anti-lock brakes use wheel speed sensors, a computer control module and an electro-hydraulic actuator to prevent hydraulic brake systems from locking up during hard braking.
• Working in conjunction with hydraulic brakes, hybrid vehicles feature a regenerative braking system that uses the electric driveline to initially slow a car. The hydraulic brakes ultimately bring the vehicle to a stop.
• Parking brakes , independent of the hydraulic or regenerative braking system, are used to apply rear brake assemblies.

What Are the Main Parts of the Hydraulic Braking System?

Master cylinder.

When you press the brake pedal, the brake linkage (rod) pushes on the master cylinder's internal piston seals, pressurizing and forcing brake fluid into the brake lines, brake calipers and wheel cylinders. This causes the brake pads to press inward against the rotors and force the brake shoes to press outward against brake drums.

Power brake booster

Brake boosters assist drivers by multiplying the force they apply to the brake pedal. These boosters use engine vacuum, an electric pump (diesel engines produce little or no engine vacuum) or hydraulic pressure (usually the pressure of the power steering pump). This increases braking performance while decreasing pedal effort, making driving safer and more pleasurable.

Brake lines and hoses

Made of double-walled steel and multi-layer rubber and synthetic compounds, brake lines and hoses transfer pressurized fluid from the master cylinder to the brake wheel assemblies.

Disc brake assemblies

A disc brake assembly consists of a brake caliper, brake pads, disc rotor and mounting hardware.

Drum brake assemblies

A drum brake assembly consists of a backing plate, wheel cylinder, brake shoes/linings, hold-down and pull-back springs, brake drum and an automatic self-brake adjusting mechanism.

Brake switches

Modern brake systems include a brake warning lamp switch that tells the driver if the master cylinder is low on brake fluid, or there is a problem with the brake system. There is also a parking brake warning light that lets you know if the parking brake is engaged.

Parking brake

Applying the parking brake mechanically locks the rear brake assemblies to keep a car stationary when parked on a hill. It also helps stop a vehicle due to a hydraulic system failure.

A hybrid's hydraulic brakes includes all the same parts as a standard hydraulic brake system.

How Does the Braking System Work?

Hydraulic brake systems convert mechanical energy (the spinning wheels) into heat energy by transforming and amplifying the force exerted on the brake pedal. The brake pedal acts like a lever. Along with the brake booster, it greatly multiplies the force applied on the brake fluid in the master cylinder.

The master cylinder also increases brake fluid pressure, then sends pressurized brake fluid, via brake lines and hoses, to the brake calipers and wheel cylinders. The pressurized fluid acts on the caliper piston, squeezing the disc brake pads inward, clamping the pads against the brake rotors .

On drum brakes the wheel cylinders slide outward, forcing the brake shoes against the drum using a wedging, jamming action — similar to how a bicycle coaster brake works. The energy of the pads clamping against the rotors and brake shoes pushing against drums generates friction and heat. This heat-friction, along with friction generated between the tire and road surface, slows rotor and axle (and wheel) rotation and ultimately brings the car to a stop.

On a regenerative braking system, stepping off the accelerator or pushing on the brake pedal causes a hybrid car's electric drive motor to run backward. The drive motor spinning backward places a drag on the wheels and slowing the car, while also producing electricity that recharges a hybrid's high-voltage batteries. While regenerative braking provides practically all the initial stopping power, the hydraulic system engages during panic stops or hard stopping at high speeds.

Signs the Braking System Isn't Working Properly

Grinding (metal-to-metal), noisy brakes.

• Worn or damaged brake pads or shoes (possibly digging into and scoring the disc rotors or brake drums), or brake pad wear indicator rubbing against the rotor.
• Worn, rusted, missing or broken brake hardware, excess brake dust accumulation, rust build-up on rotors or drums, or a stone, rust or some other foreign object jammed between a rotor and pad.

Steering wheel or brake pedal vibrating when stopping

• Excess rotor "run-out" (thickness varies across the face of the rotor) or drums are "out-of-round," badly rusted rotors or drums, contaminated brake linings, cracked, damaged or glazed rotors or drums.

Spongy or fading brake pedal

• Low brake fluid, air trapped in the brake fluid or a leak in the hydraulic system.

Low brake, excess pedal travel

• Brake self-adjusting mechanism not working, low brake pads or shoe linings, misadjusted master cylinder push rod.

Pulling to one side when stopping

• Seized or leaking brake calipers or wheel cylinders, contaminated brake linings, faulty self-brake adjusting mechanism, build-up of excess brake dust or a front-end alignment out of adjustment.

Dragging brakes

• Weak, damaged or rusted brake hardware, seized brake calipers or wheel cylinders, collapsed brake hose, misadjusted parking brake cables or misadjusted master cylinder push rod.

Grabbing or locking brakes

• Sticking or binding brake hardware, failing or failed anti-lock wheel speed sensors, brake lining friction surfaces contaminated by grease or brake fluid or bad brake booster.

Excessive brake pedal effort

• Seized brake calipers or wheel cylinders, clogged or collapsed brake hoses, contaminated brake linings or defective master cylinder, or power brake booster vacuum, mechanical or electrical problems.

A regenerative braking system has a unique pedal feel but can exhibit all of these same symptoms.

Brakes are one of your car's most essential safety systems. Never dismiss a brake warning light or brake system problems. Disregarding brake issues can be dangerous and lead to much more expensive repairs. When it comes to your car's brakes, it's always better to be safe than sorry.

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Brake fade: what you need to know and how to fix it.

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Spend any time at the track and you’re bound to hear about–or even experience–brake fade. When 3500-pound machines get into triple-digit speeds, repeatedly turning all that kinetic energy into heat is going to have some side effects. Knowing how to spot the various heat-related failure modes–and how to correct them–is key to success in braking zones.

When we talk about brake “fade,” we’re referring to a condition where a certain amount of brake pedal travel or force produces less stopping power than it typically would. (It’s also important to remember to separate fade from actual brake operation.)

What causes that fade? At the end of the day, it’s too much heat in the system.

Different brake systems, however, can tolerate different amounts of heat. The brakes on a car tuned for endurance racing, for example, will typically feel hard and imprecise at ambient temperatures. Conversely, many dedicated autocross cars are tuned to deliver top braking performance when the system is cold. 

[How to talk brakes | Ways to turn desires into hardware]

When a brake system’s heat capacity is exceeded, however, fade manifests. And that fade usually comes in one of two flavors: pad fade or fluid fade. 

Pad Fade: Hard Pedal Yet Not Enough Stopping

Pad fade occurs when the excess temps reduce the friction between the brake pads and the rotor surface. Typically, the extreme heat causes an outgassing of the binding material used to make a brake pad. 

That gas layer reduces the friction at the point of contact between the pad and the rotor, resulting in reduced stopping force. Other possible pad failure modes from too much heat: The pad material can also liquify a microscopic surface layer or simply crumble to a fine dust.

Typically, pad fade is associated with a firm brake pedal yet insufficient stopping force–basically, brake pedal travel remains unchanged because the calipers are actuating normally, yet the pad can no longer deliver the desired stopping power. Pad fade frequently results when the pads are inappropriate for the level of heat they’re dealing with.

The wrong brake pads–the incorrect compound or just ones that have glazed over–can cause fade. Photography Credit: David S. Wallens

Pad fade can also lead to second-order negative effects on the braking system. One of the most common is usually referred to as “glazing” of the rotor. In these cases, the extreme temperatures produced by the pad and rotor interface can cause the crystalline structure of the iron rotor to change: Carbon atoms become excited enough to bond to iron atoms, producing a carbide compound called cementite.

If you’ve ever been too aggressive with too dull of a drill bit going into unlubricated material, you’re familiar with the concept of work hardening. Well, that’s basically what’s going on here. These cementite deposits are extremely hard but extremely brittle. They’re also poor heat conductors and have a much different coefficient of friction than the rest of the rotor. 

So, if you’ve experienced heat-related pad fade failure and are left with a pulsating brake pedal–what many people incorrectly call a warped rotor–you’ve likely deposited these super-hardened patches of material on the rotor face and are now feeling various frictions with every rotation.

Fluid Fade: Soft Pedal Yet Not Enough Stopping

Fluid fade can also be a problem. That’s when too much heat has transferred from the pad/rotor interface to the hydraulic fluid found in the calipers and lines. That heat reduces the compression properties of the fluid. 

Brake systems use hydraulic fluid because it’s incompressible, providing a fluid-mechanical link between the pedal and the calipers–the things that actually squeeze the pads against the rotors. When that compressibility is altered, the results are bad for your brakes.

The wrong brake fluid–contaminated by moisture and/or just not engineered to withstand the temperatures of the task–can also lead to brake fade. (Hot tip: Grab one of these inexpensive testers.) Photography Credit: David S. Wallens

Fluid fade manifests as a long pedal with little to no initial stopping force and is caused by a compressible pocket that has developed in the fluid system due to boiling. This boiling can come from a few sources: the fluid itself, fluid that has had its boiling point reduced by the emulsification of water molecules, or water that has intruded into the fluid lines. 

In any of these cases, this boiling produces an air pocket–which is definitely compressible–and pumping the pedal just compresses that pocket. If you’re lucky, a few pumps of the pedal will compress this pocket to the point where it starts pushing fluid again. Pray this happens before the wall.

Fixing That Fade

Now, how can you rectify these failures? We’ll start with pad fade since it’s typically easiest to fix. 

[How much brakes for an endurance racer Miata? | Project Endurance Race Miata]

In this case, the answer is simply to use an appropriate set of pads for your application. A great deal of pad fade can be traced to OEM or cheap parts-store pads simply not being up to the elevated temperatures seen on track (although most OEM pads these days are much better than they were just a decade ago).

Any reputable brake company will publish ideal temperature ranges for a given set of pads and provide detailed descriptions of the best use cases for each compound. That’s not just marketing speak, even if a lot of it is wrapped up in flowery language. Those descriptions cover the physical characteristic of each compound so customers aren’t surprised when entering that first corner.

Proper bedding of new pads and rotors can also ensure that those pads enter their proper operating temperatures protected from uneven heating. Bedding is the process of bringing pads and rotors up to temperature in a steady, controlled fashion. With new components, this transfers a layer of pad material to the rotor in an even fashion, ensuring even friction across the surface. 

Skipping this step, or overly aggressive bedding, can leave uneven deposits across the rotor surface. This can lead to spot hardening, which can lead to failure and cracking, which can lead to sadness–and nobody wants that.

Brake companies usually supply their own bedding instructions, but typically the operation consists of several hard-but-not-threshold brake applications that slow but don’t fully stop the car. Once everything is hot enough, allow the brakes to cool progressively and evenly, usually while still in motion to avoid hot spots with parked pads. Again, read the instructions. 

The proper solution for many of us? Both pads and freshly bled fluid that can handle the task at hand–and, when necessary, appropriate ducting. Photography Credit: Chris Tropea

Preventing fluid fade is mostly a matter of ensuring that your fluid is up to the task and free of contamination and moisture. For the former, most track-capable brake fluids list the dry boiling temperature right on the container–in many cases it’s even part of the name. 

We recommend fluid with a bare minimum of a 500°F dry boiling point, but for heavier cars or more serious track use, something even more heavy-duty will provide additional headroom.

Remember that brake fluid can only resist boiling to the maximum temperature of its components with the lowest-boiling-point component. Put more simply, contaminated brake fluid boils easier than fresh stuff, particularly if that fluid is contaminated with water–which is more likely than you may realize.

Brake fluids are rated for both dry and wet boiling points, with the latter denoting the fluid’s performance once contaminated with just 3.7% water–theoretically, that comes from just two years of normal street service.

Remember our hypothetical minimal fluid carrying a dry rating of 500°F? Adding 3.7% water pulls its wet boiling point down toward the 300° mark. A motorsports-grade fluid carrying a dry boiling point close to 600° would only be good for about 400° once “wet.”

The repeated heating and cooling of brake systems is actually a pretty good moisture magnet, and it’s worth testing your brake fluid for moisture about as often as you check your oil. A $15 moisture tester can be an easy-to-use, instant-check device. 

Brake fluid showing any signs of moisture should be flushed and replaced. If you live in a hot, humid environment, this probably means after every few track events–if not even more often. At a bare minimum, cars that see occasional track use should get annual brake fluid changes, particularly if they’re driven home from a hard weekend of track use and then parked for weeks at a time.

Also, remember that whenever brake fluid boils, its physical properties are altered such that it’s far less able to resist boiling again. Any brake fluid that boils, dry or wet, should be flushed before the next session.

We’ve said this too many times to count, but brakes are the most powerful speed-altering device you have at your disposal. They’re also the only thing keeping you out of the gravel (or the tire wall) beyond the next braking area. 

Learn to recognize the signs they give you when they’re working beyond their capacity, and they’ll keep treating you well lap after lap.

What About the Ducts?

Your brakes don’t live out in the free air. They’re entangled in the suspension, bodywork and wheels. If cooler temperatures keep everything happy, proper ducting might also be part of your braking recipe.

[Building Bargain Brake Ducts From Porsche GT3 Parts?]

Brake Fluid Boiling Points

How fresh is your brake fluid? And which one should you buy next? The boiling points are often the big difference, but that extra headroom can cost a few more bucks. 

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Just out of curiosity, had anyone ever experienced pad fade on track? I've experienced fluid fade, but never personally had a pad fade.

In reply to BA5 :

Yup. A coworker of mine overheated some Hawk HP+ pads badly enough to send him far off the track. I've had various pads hot enough to start to fade but have never let them get that far. 

Yup. It was also Hawk HP+'s. I lost the pads entering T2 at Laguna Seca in my STi. I started pressing the pedal as usual and it just kept going down to the floor. A little e-brake got the car to rotate just as I left the track. I was about 5ft into the gravel trap and decided to see if the awd would pull me out. Luckily it did. There was no previous feedback that the pads were overheated.

Nursed the car back to the pits and pulled the front wheels off the car and the pad material poured out of the wheels like sand at the beach. Haven't used Hawk pad since that event.

myf16n said: In reply to BA5 : ... I started pressing the pedal as usual and it just kept going down to the floor...

Wouldn't that be fluid fade?

Yep that would be fluid fade, with pad fade the pedal doesn't really travel further than usual and certainly wouldn't go to the floor. You would find yourself using more pedal force than usual and not getting as much braking, the pedal may be pressed down a little further because of this but it would not be soft.

I'm sure the fluid boiled too, but it was definitely pad failure. They didn't fail by becoming glazed. They were only a few days old (full thickness) when this happened, and when I removed the pads in the pits there was no braking material on the backing plates. Zero. The pedal went to the floor as I was braking at T2, but it did come back enough to allow me to get back to the pits without relying on the e-brake. I'm pretty sure that the additional pedal travel was mostly related to the additional travel of the caliper pistons due to the loss of pad material.

EDIT: I read "pad fade" and jumped in with comments about pad failure. Sorry for taking the discussion down a different road.

BA5 said: Just out of curiosity, had anyone ever experienced pad fade on track? I've experienced fluid fade, but never personally had a pad fade.

Sure, at the basic level it manifests as a brake pedal that you have to push harder to get the car to stop.  Mild cases you may not really notice, but if you're paying attention then there's plenty of warning before it gets to the level of Keith's coworker. :)

Also, the number of brands of high temp fluid is impressive these days.  Used to be there were only 4 or 5 entries on most lists you could find, with Motul 600 being second only to Castrol SRF.  Now that Motul is in the bottom half!

You usually get an olfactory warning before pad fade - the person riding shotgun in that Miata that went off track could smell it on the lap leading up to the failure. But my coworker was new and I think he wanted to impress everyone with his speed and, well, there was some bad judgment.

Overheated pads feel a lot like glazed pads. They just lose their mu. They can also start wearing very rapidly if they're outside their comfort zone, which may be what happened to myf16n.

I abused the brakes on an ITC Corolla so bad that I cooked the wheel bearings. My friends who owned the car had used a really high quality Motul brake fluid so it never boiled but the pads disintegrated.

The brake pedal remained solid the whole time but there was less and less braking with each lap. I finally started chucking the car sideways to slow it down for the faster corners and only using the brakes in the two hairpin corners.

The right front wheel bearing (what was left of it) seized on the last lap causing me to spin and handing the lead back to a friend in a 510. Note I'd been instructed to drive the car as fast as it would go regardless of the consequences (The two guys that owned wanted to see what it would do and reveal any weak spots).

The metal parts of the pad had turned blue; the rotors were also trashed but they were able to salvage the right front spindle.

I don't remember what brand of but they were something better than the basic street pad. Thankfully the car only had a top speed of about 90mph so scrubbing off 20mph for the corners wasn't that hard. 

I'd sure hate to experience pad fad in a big BMW on a track with heavy braking.

I have had brake fade on my GTO (fat and heavy). The pedal was still good and firm, but no mater how hard you tried to push, the car just would not slow down. It was like the pads had been greased and you were not along for the ride. 

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Calculator for PEDAL STROKE CHANGE

• A negative percentage indicates a decrease in stroke. • A positive percentage indicates an increase in stroke.

- A shorter stroke requires a higher pedal effort to generate the same hydraulic pressure. - A longer stroke will reduce the effort required to generate the same hydraulic pressure.

The numbers already entered are just examples and can be overwritten.

Stroke of brake pedal will change  %

To predict pedal stroke before you install different master brake cylinders, do the following: » measure current stroke » compute predicted change » add calculated percentage to current stroke

This calculator calculates the change in brake fluid displacement after changing the Master Brake Cylinder(s).

Not all pedal travel is related to brake fluid displacement and therefore will not change with different master cylinders. Here are some examples: - Travel to pick up slack between the pedal, pivot point, push rod and master cylinder, etc. - Travel to make up for flex in the pedal assembly and fire wall.

Here are some actions that require pedal travel AND brake fluid displacement: - Closing the gap between pads and rotors.    [a bigger than normal gap while driving, can be caused by worn wheel bearings or warped rotors] - Expansion of brake lines.    [minimize the number of curves and replace rubber lines with SS braided lines to limit this] - Flex in calipers.    [monoblock calipers usually are stiffer than halves bolted together] - Aligning sliding calipers on worn bushings or with tapered worn pads.    [you can replace rubber bushings with brass ones to reduce these problems]

• For this Pedal Travel Calculator (that only calculates the difference in stroke between the "old" and "new" situation), it does not matter whether you are dealing with a tandem M/C or a dual M/C set-up.

• If you are working on a vehicle with one single M/C operating all four brakes (most cars of the 60's and older), than fill out either the "front" fields or the "rear" fields (leaving the other two empty).

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Brake Pedal Travel

Ford Escape Soft Brake Pedal: Causes + How to Fix

Dealing with a soft brake pedal on your Ford Escape can be dangerous and frustrating. You should absolutely not drive your vehicle until you track down the problem.

While tracking down the problem sounds daunting, there’s a lot you can do at home to get a hard pedal.

One possible cause of a soft brake pedal in the Ford Escape could be air trapped in the brake lines. Your brake system should remain closed, meaning air shouldn’t get inside.

However, air can get trapped in the brake lines, especially after service. Another potential issue could be related to the ABS pump. A failing ABS pump can sometimes cause a low brake pedal.

Causes of Soft Brake Pedal in Ford Escape

Brake Fluid Leak (Air in the System)

One possible cause of a soft brake pedal in your Ford Escape could be a brake fluid leak. If the leak occurs in the brake lines or connections, air will enter the lines.

Unlike brake fluid, air can be compressed, creating a spongy or soft pedal feel. The soft feeling is air compressing before the brake fluid moves.

To determine if there is a brake fluid leak, carefully inspect for any indications of dampness or fluid presence in the vicinity of brake lines, fittings, and calipers. These areas are likely to be the source of the issue.

• If you’ve recently installed a new master cylinder in your Escape, you’ll need to bench-bleed it to remove all the air from the system.
• A blown brake line can cause a very soft pedal. You will get the brake warning light if the pressure is too low. There will be brake fluid everywhere under the vehicle, and the change would have been instant.
• Open the master cylinder. Is the fluid level in the normal spot? Is it low? Do you see any air bubbles in? Tap it gently with a socket extension and see if any air bubbles rise.

Defective Master Cylinder

A defective brake master cylinder can be another reason for a soft brake pedal in the Ford Escape. When you press the pedal down, it is responsible for generating hydraulic pressure for the brake system.

If it is bad, the brake pedal might feel soft or spongy.

Inspect the master cylinder for signs of damage or wear, and consider replacing it if necessary. If you need to replace it, don’t forget to bench-bleed it.

Worn Out Brake Pads

Worn brake pads can also contribute to a soft brake pedal because there’s more distance for the piston to travel when pressing the pad into the rotor.

Check your Ford Escape’s brake pads for signs of wear and replace them if needed to ensure proper brake performance. This can easily be done at home by pulling one of the front wheels.

Poorly Adjusted Rear Drums (If Equipped)

If your Ford Escape is equipped with rear drum brakes, poor adjustment can lead to a soft brake pedal.

Inadequate drum brake adjustment can cause the shoes to be too far from the drum and, in turn, lead to a spongy pedal. Properly adjusting the rear drum brakes can alleviate this issue.

• Most drums or self-adjusting when stopping in reverse.

Compromised Brake Booster

A compromised brake booster can also result in a soft brake pedal. The brake booster assists in applying force to your Escape’s master cylinder, and a failure in this component can lead to reduced braking performance.

Inspect the brake booster for signs of damage or malfunction, and consider replacement if needed.

What Happens When You Push The Brake Pedal (Understanding the Braking System)

When you push the brake pedal in your Ford Escape, you initiate a series of events in the braking system that helps to slow down or stop your vehicle.

Understanding the basic principles of this system can help you diagnose common issues, such as a soft brake pedal.

At first, pressing the brake pedal creates mechanical force, which is transferred to your Escape’s master cylinder. The master cylinder then transforms that force into hydraulic pressure within the brake lines.

This hydraulic pressure activates the brake calipers, which in turn, apply force to the brake pads. The brake pads make contact with the brake rotors, generating friction and heat, ultimately slowing down the wheel and your vehicle.

Your Ford Escape’s brake system operates efficiently due to incompressible brake fluid that transmits 100% of the force applied to the brake pedal to all four brakes. However, when there’s air in the system, it becomes compressible and leads to a soft brake pedal.

Keep in mind that properly functioning brake fluid is critical to the overall operation of the braking system. Over time, brake fluid can become contaminated or lose its effectiveness, which can lead to a soft or spongy brake pedal.

Regularly checking and replacing brake fluid, as recommended by your vehicle’s manufacturer, will help maintain the efficiency of your Escape’s braking system.

Maintaining the condition of brake components such as rotors, pads, and calipers is also important, as worn or damaged parts can negatively impact the performance of the braking system.

Regular inspections and timely replacement of these components can help prevent soft brake pedal issues and ensure the safety of you and your passengers.

Diagnosing Soft Brake Pedal Issues

When you experience a soft brake pedal in your Ford Escape, it could be due to several causes. Firstly, make sure you inspect the brake lines for any air bubbles. Air in brake lines can lead to a spongy pedal feeling and affect fluid circulation.

To diagnose common brake issues, follow these steps:

• Check for air in brake lines:  Start by bleeding the brake lines to release any trapped air. It’s a good idea to perform a brake fluid change if it hasn’t been done recently, as old fluid can contribute to the issue.
• Examine the master cylinder:  A worn or leaking master cylinder could also be the culprit. Look for visible brake fluid leaks and ensure the brake warning light is not on. If there’s a leak or the master cylinder is in poor condition, it should be replaced.
• Inspect brake pads and rotors:  Improperly installed or worn brake pads and rotors can cause your Escape’s brake pedal to feel soft. Check your front and rear brake pads, ensuring they are in good condition and installed correctly.

Remember, addressing any issues as they arise will help you maintain your Ford Escape’s braking system more efficiently and ensure your safety on the road.

Prevention and Maintenance Recommendations

To maintain optimal performance and prevent soft brake pedal issues in your Ford Escape, follow these recommendations.

Regular brake fluid replacement:  One of the major causes of a spongy brake pedal is air in the brake lines. To prevent this issue, be sure to replace your brake fluid as recommended by Ford.

Inspect brake lines:  Over time, rubber brake lines can degrade and cause a soft brake pedal. Regularly inspect your brake lines for cracks, bulges, or other signs of wear. Replace them as needed to maintain proper braking performance.

Bleed your brakes:  Whenever you service your brakes or replace the brake fluid, be sure to bleed the brake system. This process removes air bubbles from the lines, ensuring a firm pedal feel.

Proper brake pad installation:  When changing your brake pads, be sure to follow proper installation procedures to avoid air entering the brake system. Check your owner’s manual or consult a professional technician for guidance.

Addressing master cylinder issues:  In some cases, a malfunctioning brake master cylinder can cause a soft pedal feel. If you suspect a problem with the master cylinder, have it inspected and replaced by a qualified technician.

By following these preventive measures and conducting regular maintenance on your Ford Escape’s braking system, you can help ensure optimal performance, safety, and longevity.

Should You Drive Your Ford Escape With a Soft Brake Pedal?

It is generally not advisable to drive with a soft brake pedal , as it can pose serious safety risks for you and other road users. A soft brake pedal may not provide sufficient braking power, leading to longer stopping distances and potentially causing accidents.

While it may not always be an immediate emergency, it is crucial to address the issue as soon as possible.

To ensure your safety and maintain your vehicle’s optimal performance, it’s best to consult a professional mechanic or a Ford service center when you notice a soft brake pedal.

They will have the knowledge and tools to inspect your vehicle, determine the root cause, and recommend the appropriate repairs or adjustments. Don’t put yourself or others at risk by driving with a compromised braking system; address any issues immediately and prioritize your safety on the road.

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brake pedal travel

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So I recently got this car and have replaced rotors and pads but not touched the hydraulics. Fluid level is good and the color is still pretty clear. The brakes work well and have decent feel. The weird thing is at a stop the pedal goes basically all the way to the floor. It doesn't just fall at a steady rate, but if I push hard after I've stopped it goes down further. It never releases the brake, the car never rolls and if I drive it feels fine. Is this normal with these vehicles or is the master starting to go on me? I know different cars have different pedal feel. Just curious what others have noticed.  

Subarus are known to have spongy brake pedal, my 3rd gen is similar. I also just replaced brakes and had a soft pedal after removing some fluid because of compressing all 6 pistons. I was worried about having to bleed them at first. After letting idle and pumping the brakes a few times it improved. Now after about 200 miles it feels great. It is still a bit on the soft side for my liking but some of that is likely firewall flex, a common complaint with all Subarus in addition to spongy pedal. There are master cylinder brace kits available to help alleviate the issue, which can get worse with spirited driving and extreme braking duties. How long ago was brake service done? Were they bled? Is it better or worse than before?  

No bleeding from me, I don't think the PO did anything. It was basically out of rear brakes when I bought it and the fronts where half gone. I'm sure the PO had pads thrown on the front and that's it.  

I've had several Subies but mostly high performance models IE STis and WRX and they've never felt quite like this. My old 99 outback is kinda crappy on the brakes but that's because they're tiny. LOL  

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Brake Pedal Travel

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I just replaced pads and rotors on my son's 01. The brake pedal seems to have way to much travel in it compared to the other vehicles we have. I checked the brake cylinders for leaks - none. The only thing I can think of is, 2 years ago he was in the DC area for the summer and the front caliper chocked and we had to have a shop replace. I am beginning to think they didn't bleed them properly? I asked him when the excessive travel in the pedal started and he he doesn't recall. I am thinking I'll bleed them again and see if there is an improvement. My other though is the master cylinder is going bad? Any thoughts/past experience on this matter? Thanks, Tim  

If I'm going to replace the pads and rotors I'll also replace the calipers, especially living in the salt/rust belt. I did a complete brake job on my 04 about 5-6 years ago then had to replace the front calipers, pads, and rotors again last year mainly do to the right front caliper locking up. When doing the first caliper replacement I let the master cylinder go dry which was likely a mistake. In using my Motive power bleeder and manual bleed procedures I had one heck of a time getting all the air out of the master cylinder. At least I bled all the old fluid out while adding new but have never seen so much of a problem getting the trapped air out of the MC. Did a master cylinder bench bleed about 3 times off my WJ then finally ended up doing a bench bleed while it was attached to the brake booster. Believe I'd start by bleeding all all the calipers and pushing all the old fluid out while never letting the MC reservoir go dry. Good luck.  

The OP's vehicle may be old enough for rubber brake lines to collapse, interfering with return pressure? My '98 developed that issue a couple years ago, so it may be time for the OP to replace rubber hoses.  

Try bleeding it first making sure all air is out of the system. If you still have a low pedal, replacing the master cylinder is good advice.  

Are your rear brakes disc or drum? As I recall the WJ could come either way. If it has drums, your rear shoes are probably out of adjustment. That causes a lot of pedal travel.  

This. ^^ Check your rear brakes whether or not it's drum or disc.  

On mine the rears are disc. I believe it does have rubber brake lines but I did take a look at them when I was in each wheel area and they looked OK but who knows when under pressure. I am going to bleed them and see what happens, if it doesn't resolve it I'll move to the next step. Thanks guys for all your input. I'll update on this as I go. Tim  

plimbob said: On mine the rears are disc. I believe it does have rubber brake lines but I did take a look at them when I was in each wheel area and they looked OK but who knows when under pressure. I am going to bleed them and see what happens, if it doesn't resolve it I'll move to the next step. Thanks guys for all your input. I'll update on this as I go. Tim Click to expand...

I had a bad ABS module. The mechanic replaced it with a used one. The pedal now travels a long way before the brakes catch. They thought that the master cylinder was bad, so they replaced that. The pedal travel is still so long it feels more like a clutch pedal. They said that they bled it 3 times with a scan tool to operate the ABS pump while bleeding. What can I do to fix this?  

You've added a new question to someone else's thread. While not a horrible thing to do, it's probably best to make your own if you can. Otherwise, we'll need more info such as ...what vehicle is this for?  

I have a 2001 grand cherokee with a 4.0L. Sorry about hijacking someone's thread. Sent from my SM-G781U using Tapatalk  

b 4 and after brake work and bleeding as good as i can, my pedal has always been soft. car stops great so i call it ok. check rotor temp with ir gun after coasting to stop. all about the same,not hot!! i find a place where i can drive ? a mile with no brakes. coast to stop. rotors should be cold...no drag.  

If it is the master cylinder it will get worse and you will have to change it. If the vehicle stops fine now it may be ok. I don't think WJ's have excessive brake pedal travel compered to other vehicles.  

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Too much brake pedal travel after rear pads and rotors

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2017 WK2, installed Bosch quiet cast rotors and ceramic pads in rear. Now has more brake pedal travel than before. Everything I read says it seems like air in system, but how would that happen? The system was never opened to introduce air. Only thing I can think of is when compressing caliper piston it somehow allowed air in? I've pumped them up at least a hundred times. E brake works, and the pads are engaging the rotor on both sides. I have same brand rotors and pads on another car and they are great. Not sure what the deal is. Saw another thread that mentions using a motive power bleeder so I guess I'll try that. Is this normal when replacing brakes on these? Anything to do with it being Bosch ceramic pads? Other possibilities?  

Yes, bad calipers or Master Cylinder, forcing the pistons back with a C clamp to back flow the system against the seals can cause the seals to get damaged if they are already deteriorated, and that can cause the pedal to feel like there is air in the system. The WK2 seems to come with brake fluid that gunks up faster than most (or a component in the system is deteriorating quickly and putting gunk into the fluid). When you force the pistons in the caliper back into their cylinder you force the fluid backwards through the system, if you have any seals the system are deteriorating, this could be enough to blow the seals or make them worse. The calipers can have gunk collect on the piston near the seals, and the seal fails to scrape it all off and it compromises the sealing or the gunk damags the seals. Then, keep in mind the front calipers are two piston calipers. This got me. One piston can be faulty and the other operates properly, so you get braking from the one piston squeezing the pads, but the pedal doesn't reel right because the bad piston is not moving right. My brakes were a mess when I got my WK2 used. The brake fluid was black with lots of debri floating in it. Fresh fluid didn't change anything. The Master Cylinder blew the first time I tried to bleed the brakes (common for a Master Cylinder that is failing, pushing it through full stroke many times, pushing the seals into the gunked up areas, results in completely blowing the seals). New Master cylinder resulted in air in the ABS unit and only using an OBDII tool to activate the ABS Pump can clear it (Most vehicle you can flush air through the ABS unit and successfully bleed the brakes without having to activate the ABS pump). When I finally finish the Master Cylinder and fully bleeding the brakes, the pedal still did NOT feel right, it was too soft and inconsistent, sometime firm, then the next pump soft. I lived with it, till I had a front caliper stick and kept the brake on. I replaced the caliper with a rebuild, and notice the brake pedal improves a lot. The old caliper had one piston seized, stuck with gunk, the other piston operating somewhat normally. I test all the calipers, by pulling them and opening the bleed port, pushing the piston in, only the new rebuild and one rear caliper (rears are single piston), could I push the piston in by hand and it moved smoothly, all the other pistons if I could even budge them by hand, they move inconsistently and soon got hung up and stuck. My system was totally gunked up and it was destroying the whole system. I replaced the rest of the calipers and the hoses, to get rid of the remaining gunk, after bleeding it thoroughly, my brake pedal finally felt normal, firm and repsonsive. So I go the extra distance and replace the plastic reservoir, because it also was coated with gunk inside it, and it wasn't flushing out. Then my Booster started leaking vacuum, that likely needs replaced now. Perhaps it the check valve, but the early WK2's are known for rusting boosters that start to leak and bleed down to quickly.  

Another sign of a bad master cylinder, push the pedal all the way down and yank you foot off it, the pedal should come up as fast as you pull your foot away, if it doesn't and comes up slower than you can lift your foot off it, i.e. you can actually pull your foot away and off the pedal as the pedal returns slower than your foot. Thats a big sign of a bad master cylinder, but not the only one. i.e. the pedal can return normally and it still be bad, but if the pedal does not return normally, thats a bad master cylinder.  

Thank you for taking the time to respond. That is a lot of useful information. As soon as I got home I bled the rear brakes with an assistant. No change. The fluid was still see through and no debris. The brake pedal does not return as fast as the accelerator pedal. It returns quickly but not as you described. I guess the next step is look into testing the master cylinder further and determine if that is definitely bad, and to check if the caliper cylinders are stuck. Thank you, this has been very helpful  

Pro tip: open the bleeder to let the crappy fluid out of the caliper when you push the piston(s) in.  

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Brake pedal travel

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Have a 2011 Heritage The rear brake pedal has way to much travel , I know this is a problem but what is the fix for it.  

Does your bike have ABS ?  

no it don't have ABS  

My 2011 Heritage has ABS Sent from my SM-G900V using Tapatalk  

OK then I would try bleeding the rear brake at the caliper.  

was thinking of that but don't know how air would get in unless fluid is low I don't see a leak Going to switch out the fluid when I try this I see it is needed every 2 years  

Someone could have changed the brake light switch and gotten air in the system.  

Plenty of material left on the rear pads? Is the caliper freed up and operating normally?  

Check your pad thickness. It can be done on the bike with a flashlight and some contortion or mirror. I forgot the spec. HD uses for min. thickness, but it is about the thickness of a credit card! I replace mine way before that.  

I don't know if you bought a used or new Bike or how many miles the Breaks have on them. Most people use the Rear Break to stop. Me I use the Front because it's a lot easier to replace the PADS in the Front. Anyway to much travel is the first sign you need to check the Brake Pads. Probably your a few miles away from hearing the Rotors grinding. First I would Pull those Pads off and check them. When Harley assembles the bikes they put the right amount of Fluid in the Reservoirs, as the Break Pads ware the Fluid level will go down in the Reservoir causing Travel. If you fill up the Reservoir and you need new brake pads, you will not be able to compress the Brake Caliper Hydrophilic Plunger. Also to accomplish that task use a big C Clamp. That's what I would do, Good Luck!  

Ok I changed the fluid in the rear brakes and used a brake bleader pump on it. I have brakes I did notice when the pump was sucking out the old fluid that a single air bubble Had to be the problem How it got in there thow I have no clue. Thanks guys It a easy fix and now ill be changing the fluid out once a year The fluid was bad looked stringy I know I have never changed it in the 3 years I had the bike. Now should the front fluid be changed also It works fine but is old fluid also. Thanks again for the advice and tips  

Yes do the front and avoid problems down the road.  

Harley spec is to change fluid every 2 years. There's even a note about it related to the abs recall, that if brakes are not flushed every 2 years, the abs recall is basically voided (may have this wrong, so check the info for yourself). If you've owned the bike for 3 years, then change the front fluid and check pads while you're down there. From my 2014 service manual, min pad thickness is 16 thousandths. Eff that, that's way too thin! Sent from my SM-G950U using Tapatalk  

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