Brake calipers come in a lot of different sizes and styles but they all do the same thing. They push friction material – that’s the brake pads, to you and me – into the spinning brake disc, slowing the rotational speed of both the disc and the wheel it’s attached to.
Here’s a bit of context. The most common type of brake caliper uses just one piston in what’s called a ‘floating’ setup. The brake pedal presses fluid down either rubber or braided brake lines and into a cylinder inside the caliper, where it pushes the brake piston out and onto the disc.
That’s one side covered, but floating calipers can move inboard slightly when that first pad strikes the disc. The first pad’s contact effectively then pulls the other pad onto the opposite side of the disc, creating the necessary grip to haul your speed down as far as needed. Lift off the brake and everything returns to normal.
This kind of setup works just fine for ‘normal’ cars and warmed-up hatchbacks, provided it’s lubricated and maintained properly. For everyday driving there’s no real reason to upgrade, other than for aesthetics. But better systems exist, for where there’s a demand. Heavier and/or faster cars need brakes that can handle more heat, more often, and deliver even more force to a disc with even more control at the brake pedal. That’s what multi-cylinder brake calipers are for.
As well as twin-piston floating calipers that work in the same way as above, you can get twin-piston fixed items that feature a piston on both sides of the disc, squeezing equally and – the theory goes – offering a greater feel of control at the bite point. On top of that there’s potential for more initial bite and more even wear because both pads should make contact with the disc at the same time. A twin-opposed-piston setup works really well for racy but still lightweight cars.
With more speed or weight comes the need for even better brakes. Sports cars need a wholesale upgrade with larger brake discs as well as more brake caliper pistons. Reason one is for heat management. All that extra speed and weight creates much more heat at the pads, and excess heat is the brake system’s nemesis.
Larger calipers with more pistons have larger brake pads, which resist temperature build-up better than smaller ones made of the same material. Larger rotors also shed more heat from their greater surface areas.
Reason number two is that a four-piston caliper, with two sets of opposed pistons, can be set up to squeeze the front two pistons slightly before the rear pair, which gives more modulation and feel to a good driver; useful for wet roads. The more gradual force input at the bite point can also be less destabilising if you have to brake mid-corner, although much of that comes down to specific setup.
Reason number three why multi-piston brakes are better is the simplest. More pistons equal more force. You already know there’s more friction material in a bigger pad, but more of it is being pressed against the disc at full strength. In short, multi-piston calipers can stop you faster on the road and let you brake later on track – but only if your tyres have enough grip.
Of course, larger pads are way more expensive to replace and the best brake upgrades can cost an arm and a leg to begin with, so the investment is one to consider carefully.