There are a number of elements that wear in a caliper brake system, so they should be checked for operation regularly.
Operation of the caliper brake
Pull the front brake on, push the bike forwards. The back wheel must lift off the ground. Pull the back brake on, push the bike backwards. The front wheel must lift off the ground.
Test the limit
When the caliper 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 caliper brake.
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 Brake Blocks
The caliper brake 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 wheels
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.