Some brake blocks have a wear indicator line on them but, if yours don’t, a good indication is the groves cut into the brake block. If the groves on you blocks are almost gone, it’s time to replace them. It’s important to replace your brake blocks in good time as, just behind the groves there’s a metal backing plate which could do permanent damage to your rims if you wear them down to it. It’s also important to look at the entire block as they can sometimes wear unevenly, looking fine from the top but completely worn out underneath.
If you do need to replace your brake blocks, make a note of the fitting you need. If you’re unsure about this, you can always remove one of the blocks or take a picture and bring it in to us. We’ll be very happy to advise you on what replacement blocks you need.