When you are battling it out...
When you are battling it out in the closing laps, the last thing you need is your brakes to give up on you. Fortunately, paying attention to the details is the best thing you can do to guarantee that wont happen.
If youve taken a big...
If youve taken a big shot to a wheel, even if your rotor or caliper do not show any damage, its a good idea to replace them simply to ensure you wont be making a second meeting with the wall again next week.
Notice the size of the caliper...
Notice the size of the caliper mounting bracket on this Late Model Stock. Its welded directly to the spindle to try to eliminate as much movement as possible.
Keeping the rotors and calipers...
Keeping the rotors and calipers up front cool is key. Simply route some ducting from the front bumper cover to the brakes and point it at the center of the inside of the rotor. The vanes on the rotor act as an air pump that distributes the air evenly through the rotor from the inside out. For the most airflow, cut your inlets in the bumper cover down low and toward the center.
Notice how the flex line on...
Notice how the flex line on this Winston Cup car is zip tied to the upper control arm. Its simply another precaution to make sure it wont get kinked as the suspension moves.
It may not seem obvious at first, but its an undeniable fact in circle-track racing that youve got to have good brakes to go fast. To make the most of straightaway speeds you want to brake as late as possible. To do this your braking system must work effectively to slow the car without upsetting the suspension or skidding tires. Now heres the tough part: It also has to work at top efficiency repeatedly for 25, 50, and sometimes as many as 150 laps and work just as well at the end of the race as it did at the beginning. At least thats what you should expect if you hope to have any chance of being around at the finish.
Pete Bingle is the lead fabricator for the No. 24 and 48 teams of Jeff Gordon and Jimmy Johnson. Hes been building cars for Gordon for all four of his championships. This may or may not surprise you, but his most important piece of brake-related advice for the Saturday-night car builder has nothing to do with hardware. Pay attention to the details, he says without hesitation. Its details, details, details. It doesnt matter if you have the top-of-the-line equipment, if you dont pay attention to the details it doesnt matter. Because we race in Winston Cup there is some really high-end equipment on these cars. Id bet the brake system on one of these cars costs more than what a lot of racers are spending on their entire cars, but it only takes one mistake in installation to make the whole thing useless.
Whether you are using a stock-style, cast-iron unit or a pure billet unit carved from some space-age alloy, your calipers are a prime area of concern. In the good old days the calipers often didnt fit inside the wheel and wed have to grind on them, Bingle says. Thats not really a concern any more. Now the biggest problem with mounting is eliminating flex.
To lock in the caliper to the most stable platform possible, Bingle welds the calipers mounting brackets directly to the spindle. He also cautions that this is one area where you do not want to sacrifice strength for light weight.
Caliper flex under braking conditions gives a poor pedal feel and reduces the friction between the pad and rotor; the more you can do to eliminate caliper flex the better. Put your car up on jackstands and take the wheels off, Bingle says. Have your driver mash the brake pedal like he would in a race. If you can see the caliper move you know you have some work to do.
Regular inspection of the calipersas with all parts of the brake systemis vital. At minimum, inspect each caliper after every race for cracks or other signs of stress. Also, it isnt a bad idea to regularly give the calipers a more thorough inspection, including O-rings, pistons and even the piston bores, to make sure they arent scuffing to the point that they may hinder the pistons from sliding back into the bores.
Also, if you have given the wall a good lick, I would go ahead and throw away the calipers that might be affected, Bingle adds. Even if they dont show damage, chuck em. I know it sounds expensive, but its a lot cheaper than having that caliper fall apart on you in the next race and driving the car into the wall. Fixing one wreck is always cheaper than fixing two.
How light you can afford to go on your brake rotors is the $10 million question. Generally, pushing the lightweight limits when it comes to rotor selection is counterproductive. Remember, even short races are endurance events when it comes to your brakes. The heat cycles a rotor sees during a race (from heating in the entrance to the turns to cooling in the straights) are tremendous. Its difficult to keep a cast-iron rotor from warping if it doesnt have some beef to it. Plus, unlike the Winston Cup guys, you probably would like to see your rotors last more than one race. Different tracks and driving styles require different types of rotors, so its hard to give a general guideline here. The best advice is to give your preferred brake manufacturer a call. Most of the major players have drivers spread across the country giving feedback on their products and may even have recommendations specific to your home track.
The big thing to watch out for with your rotors is runout. Runout is bumps or waves in either face of the rotor. Just like caliper flex, excessive runout in your rotors reduces braking power and decreases pedal feelusually the driver will feel a pulsation in the pedal. You can check your runout using a dial indicator gauge and spinning the rotor, but an experienced driver should be able to tell when the rotors are shot from the drivers seat. The best way to keep rotors from warping and developing excessive runout is to keep them evenly cooled (more on that later).
Finally, its important to remember that the most important time in the life of brake rotors and pads is the first few times they do their jobs. Raw pads and rotors need to be mated to each other, otherwise known as bedding in, or else you likely will get glazing of the pads and/or abnormal wear of both the pads and rotors. The standard procedure for bedding in brakes is to slowly ride around the track using the brakes really hard and very often for several laps or until the driver feels the brakes fade. Continue making slow laps, this time without using the brakes at all, to allow them to cool a bit. After a few laps bring the car in and let it sit until the brakes are completely cool.
Of course, the best way to get your rotors and pads bedded in is to buy them that way. There are companies out there that will do the bedding-in process for you on a brake dyno, and some manufacturers are selling pad/rotor combinations that no longer require the driver to bed in his brakes. Not having to bed in your brakes saves your car and engine wear and also saves valuable track time that can be better used nailing that perfect setup.
Brake lines are an area that is often ignored, and generally, once the lines are correctly installed they require little attention. Keep an eye out for leaks and dented or kinked lines and you should be fine. Bingle recommends using steel hard line as much as possible and keeping your lengths of flexible steel braided line to a minimum. The steel braid can flex and give the pedal a mushy feel. He recommends never using nylon flexible line. Also, make sure that the steel flexible line is secured and cannot get caught on a moving suspension piece or wheel. Bingle often zip-ties the flex line to the upper control arm to limit movement.
Protect the brake lines from punctures by using a flexible steel spring sleeve. Some teams insulate the hoses that run through the engine compartment, but unless you are weaving the brake lines though the cars headers, the biggest concern for boiling the brake fluid is in the calipers.
Pedals and Master Cylinders
Several manufacturers produce excellent pedal and master cylinder kits for racing. Options include nearly every configuration you can imagine and all will work if installed correctly. Bingle uses master cylinders that bolt to the engine side of the firewall. They are up high to make bleeding the brakes easier and are easy to reach. Its important to keep master cylinders and the reservoirs accessible, he says. Ive seen Saturday-night cars with the stuff hidden away under the dash. Thats fine as long as the crew doesnt forget about it. All it takes is one failure because some guy didnt feel like digging down to get to the master cylinder to cause you a lot of headaches.
Finally, if you are running a dirt car and washing it every week, think about bagging the master cylinders before turning on the water hose. Moisture is the archenemy of brake fluid, you dont want to introduce it to your system every time you wash the car.
If you can afford it, use racing fluid. If not, dont worry about it; buy a good Dot 4 fluid with the highest boiling point you can find. Care and usage of your brake fluid is also very important. When you open a can of brake fluid, close it again as quickly as possible. Exposing brake fluid to the atmosphere allows the fluid to absorb moisture. The more moisture brake fluid has, the quicker it will boil in your calipers. Its also a good idea after a hard short-track race to completely flush the brake system and refill it with brand-new fluid. Once brake fluid has been very hot or near its boiling temperature, the fluids boiling point is lowered.
Regularly bleeding the brakes also flushes the system over time. If you arent using recirculators this can be nearly as effective. During a race, the fluid in the calipers may be near the boiling point while the fluid in the master cylinders may still be relatively cool. Winston Cup teams are constantly bleeding their brakes to guard against a tiny air bubble from ruining many hours and thousands of dollars worth of effort to install the perfect brake system, and thats a good idea to copy. This may sound obvious to some but it still needs to be said: When bleeding the brakes, never, ever reuse that fluid. Why take that nasty old stuff you are trying to get rid of and put it right back in just to save a buck?
When it comes to brakes, heat and moisture are the enemies. For Saturday-night style, short-track racing, getting cool, clean air to the brakes is vital. Fortunately, because the front discs are doing most of the work, they are often the only ones that need ducted cooling. Simply route some ductwork from the front bumper cover to the rotors and calipers.
Make sure the air blows onto the center of the rotor from the inside, Bingle says. A lot of times you can just tie the end of the ductwork off to the control arm and aim it at the center. The vanes in the rotors act as an air pump thats constantly pulling air from the center of the rotor and pushing it out to the edges. So, you always want to make sure that you are providing a good supply of cool air to the center of the rotors. If you just blow air across the top you wont get an even cooling pattern. One side of the rotor will be cooler than the other and then you will get whats called a dynamic stress. Its a fancy way of saying the rotor will warp over and the brakes will start dragging.
As for the caliper, all you have to do is get air across it. What happens is when your brakes start to fade you are boiling the brake fluid inside the calipers. Its not in the rotor; its in the caliper. So, if you can keep the caliper cool, you are going to help keep the fluid cool, which will help your brakes last until the end of the night. As soon as you boil it, you are done. Theres no coming back from that.