What’s up with that tuned car in traffic beside me today?
It’s got a racing seat, sounds like a big turbo, and it’s got some pretty serious aero bits. But the brakes are squealing like it hasn’t seen service in 30 years. The owner of that fancy fast car wouldn’t let their brakes get that bad, would they? Probably not. If that well-built car is causing you audio distress, there’s a good chance that the brakes aren’t worn out, they’re just the wrong choice for the street. Because they’re the right choice for the track. This is how high-performance brake pads work.
If you start tracking your car, the first weak spot you’ll probably run into is the brakes. Well, other than the nut behind the wheel. If you’re using stock brakes, then a couple of rookie laps around most tracks will see smoke coming from inside the wheels, accompanied by that burning brake smell. A little bit of that and the pedal will start to get soft. The next thing you know, you press the pedal for whoa and nothing happens. So what went wrong? And where can you order a big brake kit?
Chances are you don’t need bigger brakes. You just need the right brake.
Brake pads, like just about everything else in a car, are a compromise. When an automaker is developing the braking system for a new car, they have a number of criteria in mind. And that probably includes them being quiet, dust free, and relatively long-lasting. Turning hot laps isn’t high on the list unless it’s a real racer. Even then, high-performance brake pads are likely still limited to certain trims or even as a dealer option.
Street pads are designed to be used at street temperatures. That means stop and go traffic or a couple of heavy stops followed by some driving. They also have to work from a cold start and in the rain. If you got in your daily driver on a sub-zero morning and your brakes didn’t work, you wouldn’t be happy. So the pads are generally safe to operate in a temperature window of around 0°F to about 600°. That seems pretty hot, but remember that there are just eight pads that are smaller than your hand doing all the clamping to stop your multi-thousand-pound vehicle. Brakes work by turning momentum into heat, after all.
Once they start to get over that 600° temperature window, they start to not stop your car as well. It’s when you’ll notice the smell and maybe the smoke. Overheating the pad means that the coefficient of friction of the pad starts to fall. Sometimes dramatically. The pad no longer grips the rotor, it just squeezes against it. So you no longer stop. And the pedal travel gets really long. Most times they’ll cool down and be ok again once you stop, but get them too hot and they can separate from the backing plate or disintegrate entirely. Then you don’t get to stop again until you replace them.
So what’s the solution? High-performance brake pads come in a staggering array of compounds for different roles. From pads aimed at autocrossers to those for occasional lapping-day users to full-out endurance racing pads that are capable of lasting 12-hours or more of constant fast laps.
While the companies that sell them don’t get into exactly what goes into the compound, they’ll all have characteristics tuned to the activity. Autocross pads don’t need to handle much more heat, but they offer more braking bite as soon as you touch the pedal. Light lapping pads will offer higher temperature resistance and a bit less initial bite. Making them easier to control on track. Race pads will be capable of handling temperatures of up to 1,600° or more. And can do it for a long period of time.
How do they do it when your original equipment pads can’t? Compromises. Only instead of smooth and quiet stopping, you get that loud grinding noise. Caused by metallic particles in the pad that help offer more stopping force. When they’re hot. They don’t really work when cold, so the first few brake applications in the morning might see you rolling through that stop sign. They make more dust, coating your wheels and rocker panels. They wear out more quickly after all that’s where the dust is coming from. They can also eat brake rotors. The metallic pad compounds grind away the rotor. You stop more quickly, even on track, but at the end of the race, you’re swapping the rotors as well as the pads. All compromises you’re probably willing to make in order to go on track, but ones that would horrify the average fast-car driver.
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So talk to your shop or the brake pad providers. Tell them your application and see if you’re willing to live with the compromises to keep your brakes working on track. Oh, and the reason you’re overheating your stock pads as a rookie? You might think that braking a little earlier and a little longer will heat them up less. It’s actually the opposite. Keep your foot on the middle pedal for as little time as possible. Brake hard, brake short, brake cooler. You might get some more life out of those factory brakes. Until you get really fast. Then, if you start overheating your high-temp pads, it might be time for a bigger brake kit. Or some extra cooling. And don’t forget to use fresh, high-quality brake fluid because it doesn’t matter how good your pads are if you’ve boiled the fluid.
This article originally appeared on GM Inside News