If your brakes are rubbing it could be down to a bent rotor, so here are some tips to help you identify the problem and how to go about straighten a bent rotor — if that's the cause of the issue.
If your brake is rubbing, first check that the caliper is aligned with the rotor.
Loosen the calliper bolts just enough to allow you to move it from side to side. Spin the wheel, then adjust the position of the caliper by hand until it no longer rubs, or only rubs at one point of the rotor.
Tighten the bolts alternately, a little at a time, until tight.
Rotor still rubbing at one point? It’ll need straightening. If it’s the back wheel that’s affected, shift onto the smallest rear sprocket, remove the chain from the cassette and hang it over the dropout. This will make it easier to identify the bend in the rotor.
Spin the wheel and listen out for a rubbing sound. Stop the wheel at the point where the rotor contacts the pads. Look down through the caliper to see which pad the rotor is touching. If it’s the right pad you’ll need to bend the rotor left, and vice versa.
Note which part of the rotor is rubbing, then rotate the wheel until the bent section is free of the caliper.
With a rotor truing tool, adjustable spanner or clean hands, pull the rotor a few millimetres in the opposite direction to the pad it was touching.
Rotate the bent section of rotor back into the caliper and look down through the pad slot again. If the rotor is still touching the same pad, repeat step 4, but this time bend it a little further than before.
If the rotor now touches the opposite pad, you’ve bent it too far. Repeat step 4, but this time bend the rotor more gently and in the opposite direction to before.
Repeat until it’s central between the pads.
Spin the wheel again, listening out for any rubbing spots. If necessary, repeat steps 3 to 6. When the rotor is no longer rubbing, put the chain back on the cassette and you’re ready to ride!
What's a rotor truing tool?
Also known as a truing fork, this tool makes it easy to bend the disc back into shape. A (clean) adjustable spanner can be used instead. Sometimes it’s easier to straighten the rotor by hand, particularly if a large section is bent.