Knowing how to properly check the operation of a v-brake will help you diagnose any problems.
Pull the front v-brake on, push the bike forwards. The back wheel must lift off the ground. Pull the back v-brake on, push the bike backwards. The front wheel must lift off the ground.
When the v-brake lever is pulled as hard as possible there must be at least another twenty millimetres of travel available. You can pull harder when you’re frightened and the system must be able to cope with this. Release the lever as gently as possible. If the system has any tendency to stick ‘on’ this will reveal it.
Lift the wheel and spin it gently, it must rotate freely and come to rest in a free position not stuck against the v-brake.
The outer cables need to be free from splits or cracks, the inner cables must not be frayed. Check for broken strands inside the lever and where the cable is clamped on the v-brake mechanism. Look for any weaknesses or signs of leaks in hydraulic cables. This is most important immediately after a crash. If the system is leaking for any length of time it won’t operate
Rim V-Brake Blocks
The blocks need to be held firmly, must hit the rim and not the tyre. There must be enough material left in the blocks to comfortably last the duration of the proposed trip.
Check the v-brake blocks won’t touch the tyre anywhere around the rim. The rim may not be a perfect circle.
Rims also wear away when used as a braking surface. Some rims have a groove to help diagnose the point when they need replacing.
Disc Brake Pads
There must be enough material left in the pads to comfortably last the duration of the proposed trip.