When we talk about track cars, or even street cars that we take to the track, an important consideration is brake cooling. Aside from high end sports cars that are made to be track ready – Porsches, BMW M cars, etc. – the brakes that come on your car from the factory are not designed to handle the heat of frequent hard stops from speeds that would get you arrested on the street. One of my favorite YouTubers, the Hydraulic Press Channel, demonstrated what would happen if your brakes continued to overheat and, by some freak occurrence, you didn’t crash. The video title says it all.
On his secondary channel, Beyond the Press, Lauri posted a video where he took his bang-around car, a 1990 Ford Fiesta, jacked it up, removed a wheel, and used his Finnish left foot braking technique to spin the brake disc with the engine while applying the brake to see what would happen under such extreme circumstances. Several cameras captured the catastrophic failure of the rotor, which, after glowing for some time, reached 1,000℃ before exploding.
This is an extreme situation that almost certainly wouldn’t happen in the real world. For one thing, overheated brakes would fail to stop the car, and excessive speed would cause a crash before the brakes got as hot as they did in the video. For another thing, the Fiesta was stationary, while in the real world air would cool the rotors as the car goes down the road or track. If nothing else, the brakes wouldn’t overheat nearly as quickly as they do in this video.
But brakes do get pretty damn hot. Glowing rotors are not unheard of on race cars as they brake hard for the turn at the end of a long, fast straightaway. But these brakes don’t explode because they are designed to handle the higher temperatures without failure. Even my Subaru BRZ, which is a fun but not particularly fast car, wears endurance racing brake pads when I take it to the track, as well as fresh high temperature brake fluid. These modifications keep the brakes from fading or failing on me under hard track use. My BRZ has almost no performance modifications, but after a track session the brakes are still too hot to touch, and the stock pads wouldn’t hold up. My endurance racing pads, on the other hand, have held up to six track days, have never faded once, and still have more of their life remaining than my original stock brake pads, which I use anytime I’m not going to the track.
Why do brakes get so hot? Because that’s what they’re for. Contrary to popular belief, your brakes are not what stops the car. Your brakes convert the car’s kinetic energy (forward motion) into thermal energy (heat) through friction between the brake pads and rotors. When you think of it that way, it makes perfect sense that big brake kits are a highly effective upgrade for track use. Bigger brakes means more thermal mass, which means they are better able to absorb and dissipate thermal energy under braking.
So if your brakes don’t stop the car, what does? Your tires, the same way they accelerate and turn the car. Whether you’re driving a simple go-kart or a Formula 1 car, everything comes down to your tires and using them effectively to make the car do what you want it to do.
For more geeky reading on brake systems, I recommend “Braking Systems…in Plain English” by James Walker Jr. of scR Motorsports. He literally wrote the book on brakes. I also chatted with him regularly during my Saturn tuning days, and occasionally crewed for his 1992 Saturn SC ITA race car under a new owner.
Geekery aside, it’s also just fun to watch Lauri’s brakes explode. It’s worth it for that reason alone, regardless of any educational value, because explosions are cool.