March 16, 2023 3 min read
The short version? You press the brake pedal, that moves some fluid around, which pushes on little pistons in your brake calipers, the pistons squeeze pads onto spinning discs, and that converts kinetic energy (motion) into heat. Car slows down. Simple.
But what if you want to slow down faster? What if you’re doing long track sessions? What if you bolted on a turbo the size of your kid brother and you’re hitting braking zones 20 mph faster than before?
Stopping distances are important, but heat management is crucial. Either way, we need to understand the major parts in the system.
Our brakes are converting kinetic energy into heat and rotors are our heat sinks. These iron discs store and dissipate the heat.
Most of the time, we’re working with plain face rotors that work well in most situations.
Drilled rotors are slightly lighter and improve initial response, but can crack more easily. You rarely see drilled rotors on racecars.
Slotted rotors can improve initial response and provide a consistent braking feel, but can wear brake pads a little more quickly than a plain rotor. These are commonly seen at all levels of motorsports.
Vented rotors have an internal vane structure that allows air to flow through the inside of the rotor. This improves cooling dramatically over a solid rotor. Different internal vane designs exist, in some cases requiring a specific left and right side rotor.
A 2-piece rotor is lighter than a conventional 1 piece (all-iron) rotor because the center section (the hat) is made of lighter weight aluminum. Properly designed 2-piece rotors allow the iron ring to expand independent of the hat, reducing thermal stress and cracks. Additionally, a smaller amount of heat is transferred to other brake components.
The caliper is what squeezes your brake pads onto your rotors. Most cars come with sliding brake calipers. They’re cheap and they work reasonably well. Pistons on one side of the discs push a brake pad onto the rotor, with another pad on the other side. The caliper is essentially 2 pieces, with one side able to move in and out when you press the pedal.
Alternatively, fixed or opposed-piston calipers have pistons on each side of the rotor, each pushing a pad onto the rotor face. The entire caliper assembly is rigid and “fixed” to the vehicle. Better performance, better feel, and better pad wear. And yes, they do look pretty cool.
So what’s a big brake kit or BBK? That’s a set of calipers designed for use with bigger discs.
The goal, other than looking good, is usually a better caliper and a bigger heat sink rather than more braking power. Brake fade, or overheated braking components, is an issue on track with temperatures exceeding what you see on the street. High speeds means more kinetic energy to turn into heat. Sticky tires reduce stopping distances and motion turned into heat more quickly. That’s all hard on brakes.
Brake bias is for another time, but a bad BBK can increase stopping distances.
Depending on the car, a good set of track brake pads and high temperature brake fluid is all you need for a day at the track. Brake pads are your friction material, designed for specific temperature ranges to do the work of converting kinetic energy to heat.
The key is choosing the right brake pads and fluid for your intended usage. Factory pads work on the street, but won’t produce the friction you need on your 10th lap on track.
Caliper piston sizes, rotor sizes, different types of brake fade, pad friction, cooling...there’s much more to heat management and brake performance. Stay tuned for more.