Motorcycle Disc Brakes Explained

Recently we had a few people asking about brake specifications and if we could explain the differences between different technologies. So we will try to explain a few of the things you can find in motorcycle specification regarding the brake system…

First the floating brake disc. A floating disc is a brake setup wherein the brake disc or rotor is mounted using rivets on a carrier, which, in turn, is mounted on the hub. The carrier enables the brake disc to move parallel to the axis of rotation. The calipers on either side grip the brake disc, so pressure is applied to both sides of the disc.

High performance motorcycles use radially-mounted calipers, which make a difference on track. However, series production motorcycle benefit from the lower weight unit. Performance-oriented motorcycle, from the Benelli TNT300s and KTM 390 Duke to the Kawasaki Ninja ZX-14R and Suzuki GSXR1300 Hayabusa, use floating discs at the front. Conversely, fixed discs are mounted rigidly to the wheel hub and use floating calipers.

For the floating caliper a brake setup moves with respect to the brake rotor or disc, parallel to the axis of rotation to the disc. Pistons on one side of the disc push the inner brake-pad until it makes contact with the surface of the disc, then pulls the caliper body with the outer brake-pad, so pressure is applied to both sides of the disc.

Combined braking. In order to minimize braking errors, some manufacturers have begun employing combined braking systems to regulate brake-force distribution between the front and rear wheels. Many ill-informed motorcyclists tend to use the rear brake of the motorcycle more than the front, where the actual weight transfer happens when slowing down, and that often leads to rear wheel lock-ups. Alternatively, those who panic brake often tend to lock up the front brake.

Either situation leads to a skid and, more often than not, a fall. To counter this, some motorcycle manufacturers, such as Honda have combined braking system on small-capacity scooters (called CombiBrake) that also engages the front brake when the rear brake is applied. The first manufacturer to use linked brakes was Moto Guzzi. The Honda Gold Wing was among the most inspiring motorcycle to use this technology and bring it to the fore.

Another question about motorcycles brakes is regarding brake fade. Brake fade is a condition brought about by repeated brake application, resulting in build-up of heat on the brakes that causes a temporary reduction of fading of braking effectiveness. It often becomes a concern for some high-performance motorcycles under hard braking manoeuvres. In racing, brake fade is overcome with the use of carbon-composite discs that manage temperature better than steel discs.

The Perimeter disc. A perimeter disc is a large-diameter disc brake that is mounted parallel to the circumference of the rim, hence ‘perimeter’. It is claimed to offer better braking due to a larger braking surface area. Some say it offers more efficient cooling, which is thanks to the rotor being mounted to the wheel rim leading to better heat dissipation. The perimeter disc was/is widely used on the front wheels of Buell motorcycles.

Brake pads or brake shoes. Brake pads are made from high-friction material designed to grip in pairs on each side of the brake rotor when brake pressure is applied. Earlier, asbestos was used, but due to its hazardous properties, it was replaced by sintered metal. There are two brake pads on each caliper. The pads are mounted in the caliper, one on each side of the rotor. They are constructed from a metal shoe with the lining riveted or bonded to it.