Brake Basics

They are more than just a pedal to stab when you need to enter a corner properly. A race car’s brakes actually bridge the gap between the power of the engine and the handling of the chassis. And, like other assemblies on a race car, they are a highly detailed, intricate and an often complex collection of parts.

Their workload is probably more than any other item on the car. Put them together incorrectly, or with the wrong combination of parts, and the results can be disastrous. On top of that, they require certain procedures that are critical for optimum performance.

It’s no wonder the top NASCAR teams have full-time, brake specialists flogging brake dynos in pursuit of victory.

Bedding In Brakes

How important is “bedding in” brakes? Very. The process for selecting the correct pads to work with the correct rotors is one thing but actually introducing the two to each other to begin working is another.

Much like seating valves or curing paint, “bedding in” fits the pads to the rotor and heats them to their operating temperature, thus curing them. In a simple sense, it makes them ready to use.

“Bedding in” also can be done away from the track if you have a brake dyno. Using the same method of heating them up to the recommended temperature, they are “bedded in” without the expense of going to the track.

Don Burgoon, president of Performance Friction,says many manufacturers coat their rotors with a material that prevents rust and may contain silicones and other slippery substances. Also, residues from the machining process require lubrication. Any leftover substances have to be completely removed from the pores of the rotor’s metal before the rotor can be totally effective.

Performance Friction has a line of rotors that never receive any rust inhibitor or machining lubricant so they can be used with ready-to-use pads.

When brakes must be “bedded in,” slowly bring them up to the correct operating temperature. This is done through a series of slow-downs rather than complete stops. Then let them cool naturally.

When there’s no track time, there’s another way. A simple painting treatment can tell the local racer if his pads are ready to race. Burgoon suggests “painting the edges with a temperature paint to make sure.” When the temperature gets to a certain point, the paint discolors due to the heat.

He also says early warning signs such as “splotches and warping” will lead to vibrating and cracking. Incorrect attachment of the hat or disc or even incorrect machine tolerances of the fasteners may cause this. This can also lead to tire wiggle, which causes more scrub on the tires when things should be smoother and with less drag. Burgoon says lightweight brake components used on superspeedways can be good for four-tenths of a second improvement.

Blaming Brakes?

Bill Swiderski, president of Outlaw Brakes, says that as race cars get closer on chassis and brake characteristics, brakes are often wrongly blamed for an ill-handling chassis.

“There’s a lot of different things they blame the brakes for,” he says. “You could actually have rotor drag because of a bad master cylinder. It’s not allowing the release for the pistons to go back into the caliber so you end up with a rotor drag. You’ll end up heating up your brake fluid. The rotors are rubbing against the pads, thus causing more friction and friction is heat.

“And then eventually, you’re going to end up boiling your fluid. A sure sign of that is when you see people going down the straightaway and you see their rotors are glowing. A lot of guys have a bad habit of just resting their foot on the brake pedal. Just the slightest little bit of pressure, if it’s adjusted just right, will cause rotor drag. So, a lot of crew chiefs will watch and see that. Then they can tell their driver’s actually doing that. And eventually, no matter how good a fluid you have, you’ll get it hot enough to boil your fluid and you’ll lose your brakes. Now you’ve got to slow down until they cool down to regain your brakes.”

Swiderski says incorrect pad selection also may contribute to poor handling. “Years ago, all the brake pads used to be asbestos. And then they had to get rid of asbestos for health reasons. So now we’ve gone to metallic pads,” Swiderski says. “They used to refer to brake pads as soft, medium and hard and a lot of people still do. But they’re not really soft, medium and hard anymore. They’re designed for heat.

“So you have to have a low temperature pad, or medium temperature pad or high temperature pad. A lot of times guys put the wrong compounds on. Like a dirt racer running 20-lap features. He’s not really getting his heat in there if he has a high temperature pad. He’s out there and he’s slamming on the brakes and it’s just not stopping because the compound’s not suited for him. Once again, they turn around and blame the brake caliper. I mean nine times out of 10, they always blame the brake caliper. And nine times out of 10, we find out that it’s other reasons besides the caliper.”

Warning Signs

Brakes often tell in advance of problems to come, and it’s not hard to read them. Advance warning comes from two separate areas.

Carl Bush, of Wilwood Brakes, says, “One is warning signs based on driver feel and the other is warning signs based on parts inspection. The number one warning sign would be if the driver felt a change in pedal feel, pedal travel or physically, the ability of the car to slow down. Changes in pedal feel and pedal value could be the result of what is often times referred to as ‘pedal fade,’ which means the fluid is no longer working within the temperature range the car is operating in.

“Now if the pedal is still firm, and the car is not slowing down, then that may be an indication of the heat range of the brake pads being used on the car has been exceeded by the amount of heat being generated between the pads and the rotor. That’s from the driver’s point of view,” Bush says. “From a crew chief or mechanic’s point of view, one of the number one things to read on the brake system is the rotors and generally give them a good visual inspection of how the rotor face looks.”

“If they’re wearing nice and even and smooth, and they seem to have a nice, even shiny face the whole way across the face of the rotor, you can normally assume that everything between the brake pads and rotor is working just fine. But as soon as you get into scoring, cracking, gouging, splotches of material spread over the rotor, then you need to look at just how hot the rotors are getting, the brake pad material being used. If it’s a matter of excessive heat, that’s when it might be necessary to either step up to a larger, heavier rotor that can manage the heat better or look at providing additional cooling to the existing rotors if the larger rotor size isn’t a possibility on the car.”