How to Adjust Disk Brakes on a Motorcycle Scooterby Chris Gilliland
Once the prevailing method for braking, the drum and shoe brakes of yesteryear are gone for the most part. Although effective enough for most situations, drum-type brakes required constant adjustment to provide maximum stopping power. Disk brakes, which rely on hydraulic power to squeeze the brake disk or rotor between a set of pads, have become the preeminent method. Providing tremendous stopping power in a low-maintenance package, disk brakes can perform without constant tedious adjustment, requiring only the occasional replacement of the brake pads and replenishing the fluid that powers the hydraulic brakes.
Replacing the Brake Pads
Spray the brake calipers with brake cleaner and immediately wipe away the cleaner with a rag to remove dirt and oil build-up.
Locate the mounting bolts that secure the brake caliper to the lower fork leg or bracket. Select the appropriate Allen or hex head socket and break the torque on the caliper's pair of mounting bolts. Remove the bolts and slide the brake caliper completely off of the rotor.
Remove the bolts that secure the brake pads to the calipers. Pull the brake pads and mounting clips out of the caliper.
Spray the interior of the caliper with brake cleaner and wipe away immediately. Inspect the pistons on the inside of the caliper for signs of damage or corrosion that can cause the piston to bind.
Assemble the new brake pads and mounting clips then install them into the caliper. Slide the bolts into the caliper and through the mounting clips then tighten to secure.
Press the brake pads in to seat the piston. If necessary, slide a flat head screwdriver between the pads to act as a lever. This will return the pistons to their fully open position and will restore brake lever "feel."
Slide the caliper over the brake rotor and onto the mounting bracket or lower fork leg. Reinstall the caliper mount bolts and tighten to secure.
Flushing the Brake Fluid
Open the brake master cylinder cover and top off with fresh brake fluid. There will be a distinct difference in appearance between fresh fluid and old, dirty or contaminated fluid.
Locate the air bleed valve on the brake caliper. Attach a length of 1/4-inch clear plastic tubing over the valve. Place the opposite end of the tube into a container or bucket to collect used brake fluid. On most motorcycles, this valve can be opened by a 10 mm wrench. Place the wrench on the valve.
Pull the brake lever in a few times then hold it in to maintain pressure in the brake line.
Open the bleed valve with a wrench a quarter to a half turn. A small amount of fluid should stream into the tube; at the same time, the brake lever will lose pressure and collapse against the handlebar.
Close the valve then release the brake lever. Repeat this process until the brake fluid in the tube is clear, then check the master cylinder's fluid level and top off as needed.
Remove the plastic hose and immediately wipe away any brake fluid that may have spilled. Tap the fittings on the brake line lightly, working your way up to the master cylinder, to remove any air bubbles that may have been trapped in the line.
Top off the master cylinder and replace the cover. Pull and release the brake lever until pressure has returned to the brake line.
- To simplify the bleeding process, you can use a suction-type tool to pull brake fluid through the lines.
- Take your old brake fluid to a local auto parts store for recycling.
- If you doubt your ability to complete this project, have the work done by a qualified technician.
- Check and double check that the brake pads are securely held in place by the clips and mounting bolts. A loose pad can create a hazardous loss of control or braking performance.
- Do not, under any circumstances, use WD-40 or similar products on your motorcycle's brake rotors. WD-40 has lubricating properties that will impair your motorcycle's braking capabilities, possibly leading to a crash or injuries.
- Be sure not to spray any painted parts with brake cleaner as the cleaner eats through paint easily.
- Brake cleaner can be dangerous if mishandled. Always wear gloves and protective eyewear when working with chemicals.
Items you will need
- Work gloves
- Eye protection
- Allen head socket set
- Hex head socket set
- Socket wrench
- Flat head screwdriver
- Brake pads
- Combination wrench set
- 1/4-inch clear plastic hose
- Brake fluid
- Bucket or container
- Clean rags or towels
- The Professional Motorcycle Repair Program; Professional Career Development Institute; 1995
- Disc Brake Tech
- Hemera Technologies/Photos.com/Getty Images