Calipers should be mounted in a near vertical position to allow the most efficient bleeding of air from the system. If calipers have two or more different size pistons then when the car is moving forward, the rotor should always first pass the small caliper piston then the large piston - i.e. the small piston is always the leading piston. On front mount (leading) calipers the small piston is on top; on rear mount (trailing) calipers the small piston is on the bottom. Consequently, with calipers having deferential piston sizes you can change a caliper from a front mount to a rear mount or vice-versa but you cannot make a RH caliper out of a LH or vise-versa. Calipers are typically marked with an arrow on the side of the caliper body indicating the direction of rotor rotation. Remember – the small pistons are the leading pistons and the bleed screws must be at the top, whether the caliper is mounted leading or trailing.
It is important that the caliper centerline be no more than .020" off the rotor centerline and that the inside face of the caliper be parallel to the friction face of the rotor.
Radial mounted calipers should be spaced out on the studs using the available Pro-System shim kits (PN # PSYSFCS & PSYSRCS) to have at least .080" clearance between the rotor outer circumference and the caliper bridge. Most installations will see a larger clearance to maintain the pad outer radius near the rotor outer radius. This allows for growth of the iron rotor when it is hot while maintaining enough clearance so that the rotor will not rub the caliper bridge.
Ideally the difference between pad and rotor outer radius should be no more than .012" either way. When initially fitting the caliper and rotor, check this dimension with a set of pads you intend to use as the pad friction position on the steel back plate sometimes varies from manufacturer to manufacturer.
In some applications, such as NSACAR, this fit is in constant adjustment to maintain clearance between the wheel and the caliper bridge. In NASCAR for instance, the steel wheel is the component with the greatest dimensional variance or runout which makes proper caliper mounting a moving target.
Pads must come in and out of the caliper without using force. Clearance between the pad and abutment plates and between the pads and rotor must be a minimum of .020" (.5mm). If they do not have this clearance then the length of the pad must be shortened or the thickness reduced. Another cause of pads being tight in the caliper can be worn or bent abutment plates. These problems must be corrected before use.
Care must be taken to never over tighten the bleed screws. Over tightening will weaken the threads, increase the seat width and eventually cause problems; not to mention breaking the bleed screw off in the caliper. Pro-System can, in most cases, repair calipers with broken off bleed screws. In the event that happens do not try to remove the bleed screw with an “easy-out”. We have seen the result of that attempt countless times and it is rarely if ever successful. Plus it makes repairing the caliper more difficult. We have repaired hundreds of calipers over the years with virtually a 100% success rate in cases where no one has tried a DIY repair first. Before you try to fix it think about how much it cost – if it’s a $100 caliper its worth a try but if it’s a $1500 caliper you might want to send it to Pro-System right away.
Pro-System sells the correct copper washers for use when installing inlet fittings or banjo fittings in the calipers. Copper washers should only be installed and torqued once for best results.
A floating mounting system is the most desirable way to mount brake rotors. As the brake system temperature migrates into the hub play in the hub and bearings can develop. The expanding and contracting of the hub and bearings plus the flex of the spindle and other components results in the caliper centerline moving relative to the rotor centerline during braking. Floating rotors are designed with .004" to .012" axial float to allow the rotor to "seek" an optimal path through the caliper. The design also allows the rotor to move radially allowing growth in diameter with less distortion during braking. Rigid mounted rotors will "cone" at high breaking temperatures as a result of distortion. This can produce judder or pedal pulsation as the rotor distorts. The pulsation can be of high enough frequency that the driver does not feel it, however the actual stopping power is reduced. In some cases the pulsation can become so bad that the car is hard to drive.
When installing rotor/hat assemblies check the float of the rotor after installation on the hub. A loss of float after all the lug nuts are tightened indicates that there are dings or burrs on the inside of the hat or on the face of the hub. This condition can cause several problems including rotor/wheel runout and brake drag. It is also possible with some studs for the knurl to protrude past the hub face after installation. This condition can also cause the hat to not seat flat against the hub resulting in a loss of float. Always check for this condition. The knurl will leave a witness mark on the stud hole inside of the hat. The solution is to remove the stud and turn down, to the correct diameter, that portion of the knurl that is protruding through the hub. Chamfering the inside of the hat to clear the knurl only reduces the bearing surface of the hat on the stud and allows the problem to resurface if an un-chamfered hat is later installed.
Most of our rotors have directional vanes and directional groves. On heavy braking tracks, make sure that the rotors are installed in the correct direction of rotation to insure the best cooling efficiency. The directional vanes should run back from the inside to outside diameter of the rotor. Directional or curved vanes offer increased dimensional stability over straight vanes. The purpose of rotor face groves is to add more bite and help clear away worn friction material debris from the face of the pads. A good grove design will help insure an even and consistent transfer layer of friction material onto the rotor face. The braking process relies heavily on the transfer layer. Some “stylized” grove designs do not help accomplish a satisfactory transfer layer. In most cases a simple 8 or 10 straight or curved grove design will give the best result. We don’t like to believe it but there is marketing hype in rotor grove design!
- The use of the front wheel bearing pre-load spacer kit
(PN # PSY9150PL) will minimize hub movement and improve overall braking performance and handling as well as increase the front wheel bearing and lubricant life in a NASCAR Stock Car.
- Check the float on the rotor after installation on the hub.
- Make sure that the knurl on the lug studs is not proud of the hub and/or drive plates.
- Premature cracks are usually caused by thermal shock.
- Hats and rotors should be cleaned by soda blasting, with "brake clean" spray or any good non-oily solvent.
- At the track frequently check to insure that the wheels are rotating freely without any residual line pressure or pad drag and that there is no interference between the caliper and rotor or the caliper and wheel.
- Rotors and pads should be inspected after races and long practice/test runs.
- If the pads are to be used in more than one event it is wise to remove them after the event and reinstall them before the next event to prevent contamination from washing the car or from oil.
- Rotors with cracks .200" long that have spread to the outside or inside edge and through the wall or cheek of the rotor should be replaced before a race or extended test run.
Rotors that have groves formed on the surface and/or show wear in thickness of more than .040" total when compared to a new rotor should also be replaced before a race.
With the modern metallic pads and high performance organic pads in universal use today it is not necessary to de-glaze pads or rotors. If you are over 55 years old you may remember this process and if you are under 50 you may have never heard of it. Either way forget it! Sanding or glass bead blasting the friction surface of either pads or rotors can likely diminish performance. If you must blast clean components of the brake system then the soda blasting technique is the only way to go.
- Simply fit newly bedded rotors and pads when the pads are worn out or the rotors are worn and/or cracked for best results.
BRAKE BEDDING - Brake Dynamometers
Pro-System was the originator of pre-bedded brake pads and rotors; both as a service and for new component sales. We developed the methods that are copied world wide today by virtually all racing brake manufactures. Pro-System brake bedding insures that all our rotors and pads are ready to run and require no further break-in consideration. We have three fully automated, computer controlled electric brake dynos that are used constantly for bedding, testing and development of brake parts. The fully automated bedding sequences use the correct inertia and cycle time for the job to insure that you are getting the highest quality parts available and that they are the same time after time. Drivers and team personal have more than enough to be concerned with during a race weekend or a private test day. You do not have to waste valuable track time or money bedding brakes. To avoid thermal shock, with our bedded rotors as well as with any rotor, they should be warmed up on the first lap. They do not have to be red hot, just warmed up and this will help prevent premature cracking that is common at some intermediate and speedway tracks (i.e. Charlotte) and on road racing circuits with long straights.
If you have special concerns or would like a unique bedding program for your pads and rotors we can accommodate such requests for little or no extra cost.
Within the racing type master cylinders offered in the market the most obvious differences are:
Some are forged and some are cast.
Overall lengths vary as do the position of the pressure out ports.
Lengths from the mounting flange to the end of the pushrod varies.
Some have built in reservoirs and others have provision for both remote mounted reservoirs and direct mounted reservoirs
There are pull type master cylinders and push type.
There are many different mounting configurations including the common 2 bolt flange, bulkhead mount, pivot mount, and so on.
There are many other differences not listed here that, along with the above, affect mounting the cylinders in a given application. These differences typically have little or no affect on brake performance for most drivers.
There are a few differences beyond those listed above which do affect performance:
The main one is the travel distance of the piston from rest to closing the reservoir port (making pressure) and whether or not this is adjustable. In a properly set up system you should have .020” (.5mm) of play in the pushrod with the pedal at rest. The better cylinders have adjustable travel distances for fine tuning so that together with the free play in the rod the travel is always minimal and its consistent in the front and rear cylinders.
Proper mounting of the master cylinders and pedal assembly are imperative to achieving optimal braking performance. Drivers can exert hundreds of pounds of force on the pedal. If any movement or flexing occurs within the mounting or firewall it will give negative feedback to the driver. The spongy pedal the driver feels as a result of any flex can be incorrectly blamed on the pads or the hydraulic system.
Dual master cylinders allow you to have two independent hydraulic systems. The use of this set-up far outweighs a single unit. First and foremost is safety. In the event of a loss of front or rear brake the driver still has the other system available to stop the car. This can prevent the car from slowly rolling out of control across the track after hitting the wall and also enable it to stop in the pits. Also, front to rear bias can be adjusted using different size cylinders and then fine tuned with the balance bar adjuster.
The balance bar is a fine tuning device only and should always be near the center of its adjustment range. If, after balance is achieved, the bar is over 5 turns to one end or the other then we recommend a change in master cylinder size to bring it back to near center. Make sure the master cylinder mounting places the pushrods parallel with and on centerline with the cylinder bores when under braking. If you are using one of the old style spherical bearing balance bars there should be .040" clearance between each clevis and the pedal (.080" total). Both of the above, if set up improperly, can cause a binding or a shortened pedal stroke.
To eliminate side to side slop necessitated by the use of the old style balance bars use the Pro-System balance bar part # PEY.100318. Refer to the listing on this site for its features. This balance bar is an economical and very accurate solution to an old problem. We also have a range of replacement billet pedals fitted with the Pro-System balance bar designed to fit Wilwood pedal assemblies. These easy to mount balance bars can be fit into to many different applications. Contact Pro-System to have a brake pedal made to fit your cars current pedal assembly.
When initially setting the brake balance, be sure the balance bar is adjusted to be parallel to the firewall under braking after balance is achieved (use approximately 400 to 50O psi for setup). Adjust the balance bar to be parallel by lengthening the shorter pushrod and shortening the longer pushrod equal amounts. Be sure to leave ample pushrod thread in the clevis for future adjustments, as adjustments may be necessary at the track if large bias changes are made. You can generate very high pressure in the shop with the car on jack stands but it probably is not representative of actual track pressures. If you have access to data acquisition you have noticed that typically the brake hydraulic pressure spikes in the first fraction of a second of the stop and then the pressure is modulated back to zero over the duration of the application. Set the balance bar parallel to the firewall under braking using an average pressure for the braking cycle – this is why we recommend using 400 to 500 psi for this set up.
Another useful tool for setting up the brake system and for tracking adjustments is the Pro-System brake gauge kit part # PSYBGK01 which allows one person to read the hydraulic pressure on each end of the car and set the bias all from the drivers seat. The clamping force on the rotor at each end of the car varies according to the piston area of the calipers and the stopping torque is a much more complicated calculation. Measuring hydraulic pressure does not take torque or clamping force into account. What it does accomplish is to offer a very reliable and repeatable measurement of relative line pressure. Recorded and used as a reference, this is a very good brake tuning tool. Over the years we have sold hundreds of these kits to professional racers who find them invaluable for tracking settings and changes at the track.
SETTING BRAKE BIAS and PEDAL FEEL:
When setting brake bias and pedal feel, keep in mind that a smaller diameter master cylinder will yield more line pressure, more pedal travel and less pedal effort for the same stopping power. The inverse is true when increasing master cylinder size.
Once a good brake balance is achieved at the track it is a good idea to take a line pressure reading front and rear for reference. This should also be done after a test or race if the driver indicates that the bias is correct. After a race inspect the pedal and balance bar assemblies, note their settings and how well the bar is centered and parallel to the firewall under the 45O psi test pressure. After all settings and pressures have been recorded then go through with routine disassembly, cleaning and service procedures.
- Pro-System offers a rebuild and testing service on master cylinders to insure that they are working correctly and are to factory specifications.
The high quality Brembo reservoirs are machined from solid stock and sized for the calipers used in NASCAR (front - 240cc; rear -l6Occ). A smaller 8Occ reservoir is available for the clutch but must not be used with the brake system. Reservoirs can be mounted directly to the master cylinders or remote with available fittings. The Brembo reservoir is fitted with a bellow in the cap that separates the fluid from the atmosphere while a vent hole in the cap prevents a vacuum developing in the reservoir. Do not puncture this bellow.
If a non-Brembo reservoir is used make sure that its capacity is such that the fluid will be above minimum level after maximum pad and rotor wear have occurred (with fully extended pistons) and that it has a bellows and a vent hole in the cap. The vent hole should be approximately .040" in diameter. Brembo caps and bellows are available for teams fabricating their own reservoirs. Custom fabricated reservoirs should be as tall and narrow as possible. It is important to avoid overfilling the reservoir. Initial heat build up at the start of a race can expand the fluid and cause pressure in the system until pad wear lowers the volume in the reservoir. Pro-System can fabricate reservoirs to your teams design or ours that will meet your requirements when the Brembo unit will not fit.
BRAKE FLUID RECIRCULATORS:
These systems circulate the small volume of fluid that is displaced with each brake application through the brake plumbing to a valve and ultimately back to the caliper. As the pistons retract upon release of the pedal, a volume of hot fluid passes into the pressure-out line where it loses temperature. The incoming fluid, from the pressure-in line, is obviously cooler. Between brake applications the new charge of cooler fluid absorbs heat from the caliper, seals, pistons, etc. With the next application of the pedal the process repeats itself. After a pit stop the pedal can be pumped a few times while going back onto the track to get fresh fluid into the calipers displacing the fluid that was heat soaked during the pit stop. These systems can accurately be called "brake system coolers" as well as recirculators. Their function helps keep the seals cooler allowing the designed amount of "roll-back" to retract the pistons and reduce pad drag, ultimately lowering system temperatures.
Brake fluid recirculators work very well in reducing the effects of fluid boil during a race or pit stop. With a good system, recovery time is minimal. Pro-System recommends two systems: part numbers SCOLCSB and BRE0505510 both work very well and have a successful racing history. Follow the manufactures installation procedure for both systems for trouble free results. Brembo brake systems do not like residual line pressure. Some other brands of recirculator systems have residual line pressure, which will cause brake drag and compromise braking performance. The systems listed above do not have residual system pressure.
- The use of any "anti-lock" valve or other in-line hydraulic device will compromise performance and could cause drag.
- Mount the recirculator valve as close to the master cylinders as possible keeping it below the cylinders.
- The best performing brake systems are ones that are kept simple and installed to the manufactures specifications.
Pro-System offers lines pre-assembled that have been pressure checked and part numbered for a teams specific length and location (i.e. chassis to rear axle housing). These unique part numbers will belong to the team for ordering their own spec lines. The cost is significantly less than buying bulk line and re-usable fittings and doing the assembly in-house while having the added confidence of tested line assemblies.
- It is recommended that rigid lines with an ID of 3/16" be used throughout the chassis because of their resistance to flex.
- AN-3 stainless steel braid Teflon should be used from the chassis out to the calipers and rear axle.
- AN-4 will increase displacement with the possibility of a spongy pedal feel. AN-4 is good for the clutch line.
- Route all lines down hill from the master cylinders and avoid loops that go up in the SS braided lines.
We also have the full line of GOODRIDGE hose, fittings and complete brake line kits.
BRAKE FLUID and BLEEDING:
There are many good brands of brake fluid on the market today. There are two factors that seperate fluids from each other. One is boiling point and the other is the recovery after a soft pedal from to much heat in the fluid. We recomend that you do not mix brands of fluid due to compatibility issues. Mixing fluids or changing brands without thoroughly flushing all lines and components in the car may cause problems. It is our recommendation for safety, simplicity and ease of maintenance that teams choose one fluid and use that brand exclusively.
- New or rebuilt calipers and/or master cylinders are difficult to bleed when empty and can consume a lot of expensive fluid in the process. Pressure or vacuum bleeding these components on the bench before installing on the car can make the job easier, quicker and more thorough.
- When bleeding a system with twin master cylinders, bleed one front and one rear caliper simultaneously in order to allow each master cylinder a full stroke and reduce the chance of damaging a master cylinder or the balance bar assembly.
- Start with the inside bleed screw and then go to the outside.
- Open the bleed screws and pump the pedal slowly waiting at least 2 seconds between strokes for the master cylinders to refill.
- Fast and hard pumping of the pedal should be avoided as air bubbles can be created through fluid cavitation inside the system.
- Vacuum, pressure, and gravity bleeding all work very well on the car or on the workbench.
- When bleeding is finished hold pressure on the system for 10 seconds while checking for leaks.
COOLING & OVERHEATING:
The very best brake cooling duct design requires that the cross sectional area of the duct be maintained from the opening in the nose to the duct exit at the spindle or upright and for the duct to be as short and straight as possible. In a NASCAR application this is near impossible to achieve with the compromises that must be made. However the closer the system is to that ideal the better the system will cool and the smaller the opening in the nose can be for a given flow. During construction, the brake duct should be the priority over fender bracing that could compromise the airflow or mounting. Build the bracing around the duct not the duct around the bracing. A simple cooling system is often the most effective.
It should be noted that in a test situation with only one car on the track it easy for premature pad wear and/or rotor grooving to occur in a hard 40-lap test run on a to 5/8 mile track. This can happen with the best cooling. Our experience has shown that the same wear rate rarely occurs during the race. You can destroy rotors and pads in 40 laps on a short track if you try. In these cases, an experienced based judgment call is needed between the driver and team regarding the premature wear.
Rotors operating constantly above 1130-F will grove and pad wear will greatly accelerate. If the red thermal paint is completely burning off the rotor then more cooling is needed immediately to avoid a potential failure in the system. The maximum heat soaked temperature that a brake system will see in a race may take 100 laps to develop on a short track. On a road course it can develop in as little as 20 laps. It can take a surprising number of laps to identify the week areas of a brake system.
In circle track racing increased wear on pads and rotors from overheating plus other temperature related problems could have another cause. A driver that rides with his left foot on the brake pedal, and/or uses several brake applications through a turn to set the car, and/or pumps the brakes at the end of a straight can cause this. These drivers are not doing anything wrong but are instead using the brakes to make the car do what they want. The data acquisition system is the best tool for identifying this. Trying different size pedal return springs can sometimes solve the problem but all to often the solution is in providing a better cooling duct system which in turn does not compromise the drivers driving style.
Here are some guide lines:
- Keep the openings in the nose vertical and as close to the center of the car as possible to be in the area of highest pressure.
- Flow is decreased dramatically by even slightly crushing or bending the ducting. Added length also decreases flow.
- The use of fans in the ducting is very helpful. The SRS line of fans sold by Pro-System are specifically designed for brake cooling and are the finest available. The smaller 3" fans used on boats are inadequate and should not be used.
- The cooling system should be under constant and never ending development. Never believe that the duct system is as good as it can be.
- It is much easier to find more air by pulling tape off a well-developed duct system than to be faced with redesigning an inadequate system at the track.
- You can get more air by simply improving the delivery system to the caliper/rotor without increasing the opening in the nose.
- On front engine cars, the high pressure in the radiator duct (in front of the radiator) is a low drag source for air to duct to the brakes. If this air can be used without raising engine temp, it is a good source.
- Pads that are constantly wearing with more than .040" of taper from top to bottom or .020" taper outside to inside indicate that there may be a cooling problem or a caliper mounting problem
- Premature grooving of the rotor or accelerated pad wear in a race condition is a sign of inadequate cooling.
- The pyrometer can be a useful tool if consistency is used in recording temperatures. If you are going to use a pyrometer then it should be used often as one reading could give the wrong indication. The same person should read the pyrometer each time, starting as soon as the car stops with the same wheel each time. It is important for the driver to use the same braking procedure exiting the track into the pits in order to have good data. The pyrometer can give unreliable data when used improperly. If using an infrared pyrometer then the emissivity should be set on .95.
- Temp stickers on the calipers are a good tool but must be read quickly when testing. If the car comes into the pits with extremely hot rotors, the heat will migrate into the caliper after the car stops. After a few seconds the sticker will give a reading reflecting the heat soaked temp in the pits and not the on-track temp. This is a useful tool to tell the highest temperature the caliper reached during a race and pit stops.
- The use of rotor paint is a better tool to measure temperature. The green goes off at 806o~F the orange at 1 0400-F and the red at 11 300-F The thermal paints reflect on track temperature, as the temperature must remain at or above a level for a period of time for the color to change. They will not change in the pits. Pro-System temp paint # TEM.100440 is a good choice of paint.
- By far the best tool for looking at brake temps is the data acquisition system that most teams now use in testing. Pro-System offers inexpensive thermocouples that are designed to run inside the pads near the rotor/pad interface and others that can be attached to the calipers. Contact thermocouples are available to run against the rotors but these only show a narrow ban of temperature on the rotor, are expensive and very fragil; rendering them not very useful in our opinion. The use of these devices is the best way to record brake temperatures and is very useful in developing ducting. This system will show temps on the track and also the rate at which the temps migrate into other components. If the cooling system is verified to be adequate by using these tools during a hard test, the team can go to the race with confidence that they will not have brake-cooling problems.
CUSTOM BRAKE HATS:
At Pro-System we have been machining custom hats for every kind of race car and street car for many years.
We have made hats for many sports cars over the years. If you have a Riley & Scott or a Porsche, for instance, we already have the information we need. If you have an Indy Light, IRL, Grand Am or many vintage cars we have probably made a hat to fit. The challenge in making a hat for a car in another location is getting the right offset. In some cases we ask for a sample hat. For instance if you are changing to a different brand or thickness or mounting style of rotor, having a sample of the original hat helps insure you get the part you need. In some cases we can improve brake cooling by incorporating our race proven designs into the hat flange. We have years experience with Brembo, Coleman, AP, Alcon, Wilwood and other rotor manufactures applications. We have machined hats for virtually every floating bobbin on the market.
For NASCAR and most circle track application hats only two dimensions and the brake rotor part number are required for a custom hat. The required dimensions are OVERALL HEIGHT (not the inside height) and MOUNTING FACE THICKNESS. To specify a custom hat, simply use the standard production hat part number and add a prefix that identifies the overall height first, and face thickness second.
PSY-80043 Hat (standard production part for a 12 bolt Brembo NASCAR rotor with 2.329" overall height with a face thickness of .250")
Because of a unique or new set-up a team requires a different size hat right front hat for the same rotor. The order number of the new hat might be PSY-80043-2.079-.50 (this would yield a hat interchangeable with the original but with a new overall height of 2.079", and a face thickness of .50")
In the case of sports car hats a typical part number could be HAT.100439 where HAT obviously designates a hat and the 6 digits are simply a dumb number. The description on our web site with this part number will give all the information needed for the hat.