MTB Disc brakes with 4-piston brake caliper
In the case of hydraulic disc brakes, the brake pads are pressed onto the brake disc via the brake caliper. The caliper is available in many variations and we distinguish the fixed caliper, the floating caliper and the pendulum caliper. The fixed caliper has crossed the floating and pendulum cliper. The pendulum caliper has only a brake piston and over a tilting of the caliper the pads are led to the discs. The disadvantage is the uneven lining wear and the uneven brake pressure across the brake lining surface. The floating caliper works similarly, also has only one brake piston and over a shift of the brake caliper (float) the pads are guided to the brake disk. This system has also not been adopted because the floating displacement of the brake caliper is an additional friction point and an additional source of error.
Today's modern brake calipers are designed as a fixed caliper with at least two brake pistons. The brake caliper sits firmly on each side and there is a brake piston on each side, which guides the brake pad over the hydraulic pressure. The advantage is the uniform braking effect, low restoring forces and even wear on the brake pads. The braking force is based on the transmission ratio of the encoder to the slave piston, so an effective braking performance can also be achieved with a 2-piston brake system.
In the case of brake discs with 4-piston brake calipers, the manufacturers' options are many times greater than for 2-piston systems. The braking force can be increased by the size of the brake pistons by the double number of brake pistons. In most cases, there is a small and large brake piston per side, the small provides for a quick brake response, the large increases the maximum brake force. The disadvantage is, of course, the increased weight and the higher maintenance expenditure due to more components.