Understand and Troubleshoot Your Motorcycle Brakes
The motorcycle brake system is simple. A lever or pedal provides manual pressure and compresses the brake fluid to the caliper, which pushes the pads against your rotor. Since the system is airtight, any air in the system will decrease allowable pressure. The more pressure, the harder the braking.
Basically anything that leaks fluid or allows that pressure to bleed off will impact your braking efficiency. When you engage the brakes but the pressure seems to fade away, it's known as "brake fade." Here's the rundown of the components.
The front brake lever engages your front brakes. The lever presses into the master cylinder and compresses the brake fluid. It should move smoothly and not stick. Typically, after a drop or crash, the brake lever can likely be bent and should be replaced. The rear brake pedal has the same mechanics, but it's engaged by your right foot. During a drop or crash, the pedal can get bent into the bike, causing it to stick or rub against the frame of the bike. Always be sure that it moves freely and comes back to start position when you release your foot.
When a lever or pedal is compressed, it engages the plunger in the master cylinder and pushes the brake fluid through the system to the caliper. It's a one way valve so once you release it, it resets and refills with fluid. If the plunger or any of the O-rings are bad, this will allow pressure to escape and the brakes will not engage fully or at all. Rebuild kits are available to fix these issues.
Brakes lines allow the fluid to travel from the master cylinder to the caliper. Any cracks or damage to the connections, banjo bolts or the line itself will allow pressure to leak out and cause brake fade. Original Equipment Manufacturer (OEM) lines are typically rubber, and for race-or-high-heat applications, an upgrade to steel-braided lines is common.
Brake fluid has a higher viscosity than water. This means that it is harder to compress than air and won't release air into the line when compressed like water. It is rated as DOT 3, DOT 4 and DOT 5/5.1. This rating mainly refers to its heat rating. Most motorcycles run DOT 4 and can be upgraded to DOT 5 or 5.1 for race-or-high-heat conditions. Heat brakes down the viscosity of the fluid
The fluid ends at the motorcycle brake caliper, which is attached to the forks and has pistons that the brake fluid pushes out. The pistons press against the brake pads and clamp down on the rotor, slowing the wheel. They also have O-rings that maintain the seal. If dirt or debris gets in there, it can cause brake fluid leaks. Rebuild kits are available for fixing motorcycle brake calipers.
Motorcycle brake pads sit in the caliper on either side of the rotor. When the brakes are engaged, the piston pushes them together and the pressure slows the wheel down. Make sure to keep an eye on your brake pads and change them when they get low. If the pad gets low enough, you will scrape metal to metal, which is bad for braking and will destroy your rotor.
Motorcycle brake rotors are fixed to the wheel. When the pads compress against the rotor, the friction is what creates your stopping power. Inspect the surface for excessive wear and make sure it's smooth. Any grooves or cracks in the surface will require a replacement.
Do It Yourself
The motorcycle braking system is really quite simple despite all the different components. The system must maintain sealed pressure to work. If it fails, you have to find the leak, which could be any of the components listed above. Once you find the leak, replace or rebuild the component and bleed the air out of the system to reseal it.