FAQs – Brakes

You might be able to use it but will need to check brake pressures. We recommend a brake pressure test gauge, like our P2360, when you are altering the brake system to ensure safe operation. The gauge includes an adapter that will temporarily replace the bleed screw in our calipers. The 1/4″-28 UNF will fit many other Drag race calipers as well. In most applications, the factory combination valve located on the frame rail will be incorrect and can cause some serious problems. It is only correct for the vehicle as it left the factory. The worst case is if the vehicle previously had drum brakes. Drum brakes operate at much lower line pressures than disc brakes and may utilize an integral residual pressure valve. This would cause the disc brakes to be ineffective, drag, and burn rotors.

Recommended brake pressure will normally get you in the ball park, but many factors will play a role in achieving optimal braking. There are all the different elements that exist between front and rear. Weight, tire height, width, compound, pressure, rotor diameter, number of pistons per caliper, piston diameter, brake pad area and compound. Always begin with the manufacture’s recommendation and adjust as needed.

The following suggestions are assuming that this is a Drag Race vehicle and you are using an adjustable proportioning valve, like our B3369, plumbed to the front brakes. To maximize braking, all four tires should want to lock-up at the same time. Many may choose not use this valve, but their braking will never be as good as they possibly could.

Front brakes 550-650 PSI / Rear brakes 1,000-1,200 PSI

These pressures should be achieved with a very hard push on the pedal, like your setting the line-lock. It will give you a comfortable pedal when your stopping the vehicle. If you don’t have pressure test gauge, take a look at the P2360.

Many believe you don’t need one, but your vehicle will never stop as good as it could. All factory cars came with them for a reason.

Optimal braking occurs when all four tires want to lock-up at the same time. There are may differences between the front and rear of your vehicle. Weight, tire height, width, compound, pressure, rotor diameter, number of pistons per caliper, piston diameter, brake pad area and compound. The chance that a modified vehicle would not need one is very unlikely. You should always check brake pressures after installing a new brake kit and follow manufacture’s recommendations. To see these parts, check out the P2360 test gauge and B3369 proportioning valve.

In OEM vehicles, they are present in drum brake systems. 10 lbs of line pressure are required to keep the wheel cylinder cups expanded and ready to start moving the brake shoes. They were either located within the master cylinder behind the brass inserts at the exit ports, or down in the combination valve. Without them, you would experience long pedal travel. For cars with disc and drum brakes, they would only be used on the drum side of the system. If you had four wheel drums and replacing only one side with disc brakes, the drum side will still need the 10 lbs of pressure.

In vehicles changing to all disc brakes, it becomes very important to get rid of the 10 lbs valve if the vehicle previously had drum brakes. The constant line pressure would cause the disc brakes to drag and overheat.

It is common in a Drag Race vehicle to mount a master on the floor or frame rail. Since it’s below the level of the calipers, the brake fluid wants to return to the master cylinder due to gravity. Assuming there are no leaks, the pistons retract back into their bores. When the brake pedal is applied, an extra volume of fluid is required to move the pistons back out to contact the pads and begin applying pressure. This creates long pedal travel requiring the use of 2 lbs residual pressure valves to offset this condition. We do offer external 2 lbs valves (B3366) and a 10 lbs valves (B3367) to suit your needs.

We recommend DOT 4 or DOT 5.1 only, and stay away from silicone brake fluid. There are some Hi Temp versions of DOT 5.1 that offer higher protection against boiling the fluid. You must be careful with brake fluid as it will soften paint if spilled. The brake fluid should be changed every year before the car is run for the season.

While in storage, condensation will accumulate in the system. One feature of brake fluid is the absorption of water. When replacing the fluid, you are also removing the water and protecting the system. When water is allowed to stay in the system, it corrodes parts and lowers the boiling point of the fluid.

Silicone brake fluid doesn’t eat paint and that’s it’s only real feature. One of the down sides are it will not absorb water like normal brake fluid. You are never sure that all the water has been removed during flushing. Once agitated, it is very difficult to get the air out of the system. If the car previously had normal brake fluid and you are switching to silicone, any amount left of the previous fluid will have a chemical reaction leading to problems in the future.

It depends on vehicle weight, MPH, rotor to tire diameter, pad surface area and compound, number of caliper pistons, piston diameter, brake pressure, stopping distance, and any other assistance such as a chute. I’m not trying to be difficult, there’s just a lot of factors to consider.

If the vehicle has four wheel disc brakes that are properly sized, proportioned, and with new pads you should possibly get half to a full season from the pads. Rotors should only be resurfaced when they show signs of warpage. Discoloration might be an indicator that a problem exists, but are not a reason for machining. Accumulation of pad material can often be removed simply with sanding disc and an air drill. If you are replacing pads more often on the front or back, and rotors show different signs of discoloration there might be an issue with the proportioning or improperly sized brakes. If you log your runs and check periodically, you will learn the pad life you can expect. At the end of the page are included specs on pads and rotors. As you will see, unnecessary machining of the rotors will shorten their life.

With two wheel disc brakes it depends on MPH and whether or not the driver is pulling the chute. Dragsters running in excess of 160 mph should always pull the chute. The chute scrubs off a lot of MPH once it is deployed and lightens the load placed on the brakes. Calculating kinetic energy in which velocity is squared, makes increased MPH a real issue. If pulled, you could expect a set of pads to live half to a full season, and rotors several years. If not, pads maybe every four races and replacing the rotors once a year. Many that don’t pull their chute, will opt for our 2 piece stainless steel rotors (B2794LS / B2794RS) which, in this case, last about two years before requiring resurfacing.

Steel Rotors – 10″ New .250″ (Discard at .215″) / 11.250″ New .355″ (Discard at .312″) / Pads New .480″ (Discard .200″) Measured including backing plate thickness.

Calipers should be rebuilt when the pistons appear to be sticking, there is leakage, subject to excessive heat such as a fire, the brake fluid is dirty, or it has been several years since the last rebuild.

Rebuilds are relatively simple. Often it’s just an o-ring kit and cleaning. The pistons are stainless steel which are normally fine. Since the caliper bores are aluminum, it’s best to use cleaners and to avoid anything abrasive unless necessary. You can use compressed air to coax the pistons from their bores. Lubricate the bores with brake assembly fluid or brake fluid, lubricate the o-rings & pistons and reinstall. Be sure to bleed the brakes and check for leaks after installation.

The brake fluid should be changed every year before the car is run for the season. Use either DOT 4 or DOT 5.1 and do not use silicone brake fluid.

While in storage, condensation will accumulate in the system. One feature of brake fluid is the absorption of water. When replacing the fluid, you are also removing the water and protecting the system. When water is allowed to stay in the system, it corrodes parts and lowers the boiling point of the fluid.

Silicone brake fluid doesn’t eat paint and that’s it’s only real feature. One of the down sides are it will not absorb water like normal brake fluid. You are never sure that all the water has been removed during flushing. Once agitated, it is very difficult to get the air out of the system. If the car previously had normal brake fluid and you are switching to silicone, any amount left of the previous fluid will have a chemical reaction leading to problems in the future.

The most common reason is one or more of the rotors is warped. If you also feel it in the steering wheel, the check the front first. More uncommon is that wheel bearings are loose, front tire pressure is too low, or you lost a wheel weight.

First consider if everything was fine until you changed something. If you are checking rotors for run-out, they should be removed from the vehicle and measures independently. For a quick check on the front rotors, temporarily tighten the spindle nut to avoid any extra play. This works but isn’t entirely accurate. You will typically feel pulsations at about .007″ of run-out. The specs are the same for the rear, but these should really be removed. The rotor is attached to the axle face near the axle bearing. The far end of the axle are splines rotating within the spool. There is clearance in the fit of the splines which is amplified by the axle length. You only want to resurface rotors that have run-out. Machining them unnecessarily reduces their life and can make them more prone to warpage due to loss of mass.

I assume that the pedal is either too hard, too soft, or has a lot of travel.

I would check the brake pressure first. Use a temporary pressure gauge like our P2360 to measure pressure directly at each caliper. It would be best for the actual driver of the vehicle to push on the brake pedal as interpretation can vary due to leg strength. While testing, look for any signs of deflection from the caliper mounts, rotor, and brake pads. If there is any deflection, it can cause a soft pedal or increased travel distance. As the driver pushes harder, pressure should increase as well. If the needle suddenly stops, even as the driver pushes harder, the master cylinder may have reached the end of the bore meaning inadequate bore size or stroke. To the driver, the pedal continues to move, but they are just compressing the override springs inside the master. This may occur only in the front, rear, or both. If the pedal suddenly stops and won’t move, the assembly is hitting something preventing further movement. If pressure continues to rise, have the driver increase pedal pressure until it feels somewhat hard, like setting a line lock. At this point, if using an adjustable proportioning valve (B3369), the front should read 550-650 PSI and the rear 1,000-1,200 PSI. If not, the pedal ratio is incorrect or the bore size of the master is too big.

Check pedal ratio by measuring from the pivot point, where the linkage attaches to the body or frame, to the center of the brake pedal pad. Next, from the pivot to the hole where the master cylinder push rod connects to the linkage. Divide the first measurement from the second and the result is your pedal ratio. At this point, you would also want to know the bore size of the master cylinder. While not completely accurate, you can remove the dust boot from the back and measure the bore of the hole before the snap ring. The recommendations for pedal ratio are based on the two most common master cylinders we sell. For the B3359 (1.032″ bore) the ratio should be 5 1/2 to 1 or the B3360 (1.125″ bore) should be 6 1/2 to 1. This should get you in the ball park, but may vary due to driver preference.

Increasing pressure may require: (1) Longer assembly increasing the distance from the push rod hole to the pedal pad. (2) Relocating the hole closer to the pivot. (3) Replacing the master cylinder with a smaller bore size. Remember that more leverage increases pressure, but also increases travel. A smaller bore increases pressure, but moves a smaller amount of fluid. When moving the hole where the push rod connects may require moving the master cylinder location to keep the push rod level.

The most common reasons are the brakes where not bed or bedded improperly, brake pressure is too low, the front to rear proportioning is incorrect, the size or type of brakes are inadequate , brake pad material is insufficient, or not pulling the chute.

New brakes should always be bed. During this process, brake pad material is transferred to the rotor surface. This creates the actual wear surface and protects the rotor. The heat generated will finish the curing process of the brake pad. Common problems associated without bedding are heavily scored rotors, pads cracking or chunks of material missing. The process is relatively simple. It consist of 8 to 10 applications of the brakes, increasing in harshness each time, and allowing the brakes to cool slightly in-between. Do not keep the brakes applied between stops. After the last stop, allow the brakes to cool down completely.

If the rotors are blued, but not warped, this may not be a problem if the appearance is the same on all. Do not resurface them purely for this reason as it will shorten their life. Low pressures generate heat over a longer period of time before the vehicle comes to rest. This can occur if the pedal ratio is insufficient or the bore size of the master is too big. If it’s just the fronts or rears, it could be a sign of improperly proportioned or undersized brakes. Check brake pressures with a temporary test gauge such as our P2360. With a very firm pedal, like setting a line-Iock, the front should read 550-650 PSI and the rear 1,000-1,200 PSI. These pressures assume that you are using an adjustable proportioning valve, similar to our B3369, to balance the braking system. If only one rotor shows excessive heat, it could be pistons sticking in the caliper requiring a rebuild. If you replace pads more often on the front, you may have high line pressure in the front, need larger brakes up front, or low line pressure to the rear. If you are replacing rear pads more, possibly the pads material might be too soft for your application. When using hard metallic pads, it is common in higher MPH cars to leave residue on the rotor surface. This is melted pad material that occurs when they are near their limit and needs to be removed when the pads are replaced. Machining is not required as it can be removed with a sanding disc and air drill.

For cars equipped with chutes it is important to use them. The chute scrubs off a lot of MPH once it is deployed and significantly lightens the load placed on the brakes. Calculating kinetic energy in which velocity is squared, makes increased MPH a real issue. If pulled, you could expect a set of pads to live half to a full season, and rotors for several years. If not, pads maybe every four races and replacing the rotors once a year. Many that don’t pull their chute, will opt for our 2 piece stainless steel rotors (B2794LS / B2794RS) which, in this case, last about two years before requiring resurfacing.

Brake pads can wear unevenly for several reasons. I will be referring to the top of the pad as the area closest to the bridge bolt of the caliper. If top is wearing more than the bottom, the brake pressure might be too high causing the caliper to spread apart at it’s weakest point which is the unsupported bottom.

If it’s one side of pad, it will wear more on the side where the rotor enters the caliper than where it exits. As the pads contact the spinning rotor, the forces try to push the pads in the same direction. Since the pads are retained in the caliper, it causes the pads to bite harder on entry and less on exit. The B5002 / B5004 calipers are designed to offset this tendency by decreasing piston diameter on entry, lowering the pressure applied to that area. While this reduces pad taper, it also reduces overall pressure on the pad. If that becomes an issue, we also have B1900 calipers that have same size pistons and stiff billet bodies that can apply higher pressures while ensuring the calipers will not spread.

If the inner pad is wearing more than the outer, and only slightly, this is normal as the brake line enters the caliper on the inboard side and pressure rises slightly quicker. If it’s more apparent, the caliper might need to be rebuilt. If front and rear pads are wearing at different rates, check line pressures as the system proportioning might be incorrect.