Different materials, different compounds are available for different types of rim. Steel rims don’t offer very good braking – with a marked loss of stopping power in the wet. Special brake blocks for steel rims help a little. Softer brake blocks stop you better but wear down faster. A hard brake block will last longer but may accelerate rim wear.
Check The Brake Block Faces
As brake blocks wear the action of the brake changes, some brake blocks – for example’V’ brakes, and one side of a dual-pivot calliper – move away from the tyre. If part of the block starts to miss the rim it won’t wear. The resulting ridge tends to hook the blocks in the ‘ON’ position so they can’t release.
Trim If Necessary
Take the brake block out of the brake if necessary and carve off any ridge with a knife. File the face smooth. If you take the block off note carefully the position of any washer.
Replace If Necessary
The blocks may have a wear line. When the wear reaches the line or they start to look thin replace them.
If the bike is used for high-performance change the brake blocks every couple of years regardless of wear as the rubber gets hard with age and the blocks don’t work so well.