Changing brake shoes on a drum brake

While a drum brake may not be as powerful as a disc brake system with a six-piston caliper, it offers more than sufficient performance for the rear wheel of smaller motorcycles, or choppers and touring bikes. If the drum brake is fitted to the rear wheel, a service life of 13,000 to 19,000 miles is not unusual, given proper maintenance. The enclosed design of the drum brake means that brake dust (abraded particles from the linings) cannot easily escape. Unlike a disc brake, you can only get at the brake shoes by removing the rear wheel. But once you've removed the rear wheel, it's an easy job to expose the brake linings.

Some drum brakes have an inspection port, which is covered by a small rubber plug. By removing the rubber plug, you can see the thickness of the linings through the port. Refer to the repair manual for the specified minimum lining thickness (you always measure the thinnest point of the lining, which is bonded to the brake shoe). The rule of thumb is 2 mm. Many motorbikes have a wear indicator in the form of a pointer on the brake lever. This points to a marking on the backing plate. If the pointer is at the end of the marking when the brake pedal is depressed, the shoes are worn and need replacing. However, you will only know for certain what state your brakes are in if you remove the rear wheel. Only then will you be able to properly inspect the entire brake pad and identify any vitrified, oil-fouled (e.g. due to defective wheel bearings) or cracked brake pads. Due to its design, the brake linings of a non-servo brake wear down slightly unevenly. This is completely normal.

Once you have removed the rear wheel, you can take the brake backing plate out of the drum. 

The shoes can be levered off using a wide screwdriver. Hold your hand (wear a glove) over the shoe and springs while doing this – it might save you a long search for the springs on your garage floor. The springs are now very easy to unhook from the old brake shoes. If your new shoes did not come with springs, never re-use the old ones if they are rusty, damaged or stretched (refer to your repair manual for max. permitted length)! However, if the springs you have taken out are OK, then clean them and re-use. 

Now clean the brake drum and brake backing plate with brake cleaner. As with all other maintenance tasks on your brakes, meticulous cleanliness is crucial.

Once you have made sure everything is clean and grease-free, check that the brake shaft is operating smoothly. If it can only be turned with difficulty, you will need to remove the shaft and clean and lubricate it. Removing the shaft is not a big job. In most cases you just need to remove the brake lever and the shaft can then be pushed out. However, before you unscrew the lever, use a centre punch to mark its position on the shaft. 

After you have cleaned the shaft, lubricate it lightly with copper paste and re-insert it in the brake anchor plate. Fasten the lever back in the position that you marked previously.

On the new shoes, apply a thin layer of copper paste to the surfaces that are in contact with the support and the brake cams. To secure the new shoes to the brake backing plate, first hook the springs back into place. Now hold the shoes under tension in a V shape, and position the shoes on the brake cam and the fixed pin. Press down on the outer edges of the V until the mechanism engages. If the lining surfaces have become soiled from your hands during installation, give them a quick clean with sandpaper. Carry out a final check to ensure that the springs and shoes are correctly seated.

Before replacing the brake backing plate with its new shoes in the drum, check the brake drum for any signs of damage. Signs of rust and glazed surfaces can be removed by sanding lightly.

However, if the brake drum is badly worn and scored in the area of the brake linings, you will need to visit your local motorcycle workshop and get professional advice as to whether the brake drum can be resurfaced or whether the max. diameter has already been exceeded. If your bike has spoke wheels, the hub can be replaced. But if you have cast wheels, you will unfortunately need to buy a complete new wheel.

Now mount the rear wheel, complete with brake anchor and brake rod. Correctly tension the chain and tighten all the screw connections to the specified torque. If your bike is fitted with disposable rather than reusable split pins, these will need to be replaced. 

Now adjust the brake. Rule of thumb for free travel is approx. 5 mm to 10 mm play at the pedal until the brake engages (check your owner's manual). It is crucial to ensure that the play is set correctly, otherwise the brake may engage too late or it may even seize if it overheats. The play is adjusted at the end of the brake rod via an adjusting nut. 

Once you have made the adjustment, turn the rear wheel by hand a few times to make sure it turns freely and nothing is rubbing (motorcycle needs to be jacked up). And to round off this job, adjust the brake light switch. If you loosen the lock nut of the brake light switch, you can turn it. The brake light should light up just before the brake engages.