🛑Braking system

How it works

The braking system is the single most important safety component on a motorcycle: it converts kinetic energy into heat to slow down and stop the machine. Most modern motorcycles use hydraulic disc brakes, especially at the front (which handles most of the braking); many models have a drum brake at the rear, while older or smaller-displacement bikes may use drums on both wheels. On a hydraulic disc brake, the chain of action works like this: the lever (or pedal) actuates a master cylinder that pressurizes the brake fluid; that pressure is transmitted, with no loss since fluid is incompressible, through hoses to the caliper; inside the caliper, one or more pistons push the friction pads against the disc, which is bolted to the wheel; the friction slows the wheel and dissipates the heat. Brake fluid is hygroscopic - it absorbs moisture over time, which lowers its boiling point (risking 'vapor lock') - so it needs periodic replacement. On a drum brake, a mechanical linkage (cable or rod) rotates a cam that spreads two lined shoes against the inside of a drum. Many motorcycles are also equipped with ABS, which prevents wheel lock-up under braking. Failure modes include: worn pads (reduced bite), aged fluid or air in the circuit (spongy lever), a warped or worn disc (pulsing), a seized caliper or master cylinder (a brake that's either hard or dragging), and pads or discs that are glazed or contaminated with grease (weak bite). Braking tolerates no shortcuts: any work on the hydraulic circuit or ABS, or any doubt about braking effectiveness, must be handed to a professional.

Maintenance tips

• ✓Regularly check pad thickness (through the caliper or by removing them): replace pads in pairs before they reach the minimum spec (often around 1.5 to 2 mm of friction material, or the wear indicator), and well before they start grinding into the disc. Check the exact figure in your manual.
• ✓Check the level and color of the brake fluid at the reservoir: clear, straw-colored fluid is healthy; dark or brown fluid should be replaced. Have the fluid bled and replaced periodically (often every 2 years), regardless of mileage.
• ✓Watch the feel of the lever/pedal: one that goes soft and sinks (air or boiling fluid) or one that's very hard (seizing) calls for inspection - any work on the hydraulic circuit should go to a professional.
• ✓Check disc condition and thickness: a warped disc (pulsing under braking) or one below the minimum thickness stamped on it ('MIN TH') must be replaced. Never ride with an undersized disc.
• ✓Every so often, clean the discs and calipers with brake cleaner (never anything oily on the friction surface) to clear away dust that causes squealing, and check that the pistons and pins slide freely.
• ✓With the wheel raised, check that each wheel spins freely with the brake released and that no brake is dragging (a disc that heats up abnormally): a dragging brake wears out, overheats, and can lock the wheel.
• ✓After replacing pads or a disc, pump the lever/pedal before riding off and bed in the new parts gently (progressive braking over the first few kilometers) to restore full bite.
• ✓At the slightest doubt about braking performance, don't ride and have it checked by a professional: this is the safety component above all others, and it tolerates no guesswork.