"We made a mistake at Sears," Busch adds. "At the end of the race we had the car to beat, but I lost the brakes because we didn't use a large enough (fluid) reservoir and we boiled the fluid away."
Some teams even change the type of material from the front and rear of the car.
"Most teams use the same friction front and rear on short tracks, but on a speedway they will use a less aggressive pad in the rear to prevent a 'loose in' condition," Gaylor says.
The less aggressive pad reduces some of the braking at the rear end, which helps prevent the rear of the car from locking up and sliding when the weight shifts to the front of the car and unloads weight from the rear tires.
"The biggest thing is to have drivers- even guys running in local short-track series-experiment with different compounds until they find something that works for them," Gaylor says. "Don't just run something because someone else does. They are like a pair of shoes, they have to feel good to the driver."
One driver may get on the brakes slightly earlier than others, but not brake as hard. Another may wait until the last moment and mash the pedal. Each type may want a different feel from the brakes.
Short Track Advice
If you are racing at Daytona in a Winston Cup car, you should be stopping with Winston Cup brakes. But if you are on a short track in the middle of Kansas, racing in a Street Stock division, heavy-duty street pads are probably just what you need. That's the advice of Charles Darsey, test manager for Dana Brake Parts, which builds Raybestos brand brakes and friction material sold under other brand names.
"One of the biggest mistakes you can make as a Street Stock driver is to go to someone's parts catalog and order what Rusty Wallace is using," says Darsey. "If your car is set up right, a heavy-duty, semi-metallic pad is probably all you need. If you are in a Street Stock and lighting up the rotors like Rusty Wallace at Bristol, you probably have other problems you need to tackle before changing brakes."
Here's some other advice Darsey offers:* Bigger is better: If the rules allow it, go to the biggest brakes you can fit on a car. "Sure, it will increase unsprung weight, and that's not good, but what it will do to the braking will probably offset that." The more surface area you have, the better the brakes will work, he says. They will heat slower and have more surface to release heat.
* Keep cool: "Air to the brakes is never a bad thing."
* Drilling vs. slotting: "It will reduce the weight a bit, but on a Street Stock car, it probably isn't worth the time and effort. The gains are marginal at best."
* Master cylinders: Darsey prefers using a single, double chamber master cylinder with a proportioning valve rather than twin master cylinders. Two cylinders share the pressure you put on the system while a single master cylinder uses all the pressure you apply everywhere, he explains.
* Brake bleeding: "It should be done at least once a month."
Cracking The Code
Performance Friction's code for labeling its racing brake pads is based on the year each pad was introduced to the racing market. The company has developed pads with increasingly greater frictional coefficients; that means that the higher number usually means more stopping power. Of course, there are subtleties. Here's a more complete breakdown to give you a better idea of how to break the code.
|Pad Number ||Description |
|80 ||P.F.'s lowest-friction pad. Not really aggressive when cold, but it does generate more stopping torque as it heats up. |
|83 ||Fair-to-moderate friction when cold. Aggressive friction ramp once it heats up. Can get so strong as to upset the chassis. Basically, the friction ramp never levels out. |
|90 ||Good initial bite, somewhere between 80 and 97. Slow ramp (less than 97) that trails off as it gets hotter. |
|93 ||Somewhat high bite. Ramps very hard, but between 1,200 and 1,400 degrees the friction ramp starts to fall off similar to 90. |
|97 ||Slightly higher cold friction than 80. Frictional coefficient ramps up even higher as it heats up. |
|01 ||High bite. Consistent frictional coefficient with no appreciable temperature ramp. |