Castrol guide: Putting a stop to brake problems
Making sure your bike or scooter stops well is more important than making it go! So understanding how brakes work and how to keep them working perfectly is essential in basic motorcycle maintenance.
There are two types of brakes, drum brakes and disc brakes. Most modern motorcycles use disc brakes, but some older bikes and scooters use drum brake systems to slow down efficiently.
This article deals with drum brakes, coming back to their disc counterparts at a later date. With drum brakes, a set of shoes sit inside a drum which in turn sits inside the wheel. When you hit the brake pedal or pull the lever, a piston pushes a set of brake shoes which sit inside the drum against the inside of the walls of the drum. When this happens, the shoes wedge themselves against the inside of the drum tighter and tighter to increase the braking force. When you release the lever or pedal, springs pull the shoes away from the walls of the drum allowing the wheel unrestricted movement.
There are two types of drum brake system: the single leading shoe and twin leading shoe. In the single leading shoe system, there is a cam which pushes one end of each brake shoe outwards to make contact with the brake drum, while the twin leading shoe system has two cams on each end of the brake shoe to push both sides of the shoe in contact with the drum.
For drum brakes to work properly, the brake shoes must remain close to the drum without touching it. If they get too far away from the drum (when the shoes wear down for example) the piston pushing the shoes apart will need more fluid to push them apart the same distance, or if the brake is cable operated then the brake lever will come further back without any braking force being applied to the drum. Thankfully you can use the adjuster to keep the shoes at the optimum distance from the inside of the drum, some machines also use an automatic adjuster.
Regular checking of drum brakes is essential. This ensures that the material left on your brake shoes is at the optimum level and not too worn down or that the glue on the brake material is still holding it to the shoe. Some friction material is held on with rivets, so check to see that the rivets don’t show through, as these will then start cutting grooves into the inside of the drum as you apply the brake.
Other potential fault areas are the brake cams, which push the shoes against the drum and are often prone to seizing. In order to avoid rusting and seizing use copper grease on all brake components, but be sure not to let the grease come into contact with the brake shoe or inside of the drum.
For maintenance, open the drum and check the wear on the shoes to see if they need replacing. If you have friction pads which are bonded on to the backing plate of the shoe, then replace the shoes when they have 1.5mm (about 1/16th of an inch) of material still showing. If you have the shoes with the friction material riveted on to the backing plate, then replace the shoes when the material is around 1mm (or 1/32nd of an inch) away from the rivets themselves.
To replace the shoes, simply lever one of them up and both will come free as they’re both connected by the springs. Then, just attach the springs to the new set of shoes and lever them back on.
Remember never to breathe in any of the brake dust, in fact wear a face mask if you have one. Give the inside of the drum - where the shoes come into contact with it - a check over and sand the area with an emery cloth. Then clean up the brake backing plate, grease the brake’s cam and pivot post and rebuild the drum.