I've had an ongoing problem with this, but as I've just fitted new pads I thought I'd try and get it sorted out properly.
Basically, when I pull the rear brake, the caliper doesn't return to the "unpulled" position when the brake lever is released. Or rather, it does return, but only slightly so one of the pads still rubs on the rim.
I've taken the caliper off, soaked it in petrol, and then in oil so it's working nice and freely. Refitted it, and I have the same problem.
If I don't tighten the retaining bolt properly, then the pads release better, but of course the caliper sits to one side so that a pad rubs on the rim anyway!
Anything I can do? this is driving me up the wall!
The caliper is a Shimano sidepull jobbie
Taken from
http://www.sheldonbrown.com/rim-brakes.html#centering
Centering Adjustment
When the brake is released, the brake shoes retract away from the
rim. Ideally, the shoes on both sides should back off by the same amount. If they don't, the brake is not properly centered. In extreme cases, one of the shoes may not retract, and may rub on the rim even when the brake is not being applied. If a brake appears off-center, check first that the wheel is installed straight in the frame/fork. If the wheel is crooked, and you maladjust the brake to compensate, you are creating two problems where there was only one before.
If the brake is, in fact, off-center, it is often the result of too much friction on one of the pivots. Unhook or loosen the cable (the
transverse cable, on a cantilever or centerpull brake) and try moving each brake arm individually by hand. They should move smoothly and freely, and always come to rest near the same position. If you suspect friction, unscrew the bolt that holds arm to the
boss or pivot, and remove the arm. The surface of the pivot should be smooth, free from rust, and coated with
grease. If it is rusty, that is usually a sign that the bicycle was sloppily assembled by the dealer who sold it. Use emery cloth or sandpaper to remove the rust, and wipe off the dust and sand. Coat the boss or pivot with grease, and re-install the brake arm.
Spring Adjustment
If your wheels are centered, and your brakes are not, and, if the pivots are properly lubricated and free-moving, the brake shoes should be centered. If they are not, you probably need to adjust the spring tension on one or both sides Different types of brakes feature different systems for adjusting the springs.
- Most caliper brakes can be centered by rotating the entire brake assembly around the bolt that attaches it to the frame or fork. Loosen the nut that secures it, and hold the bolt steady, with a wrench if possible, so that it does not rotate as you retighten the nut. On some older and cheaper caliper brakes, including those on many English 3-speed bicycles, the return spring is rigidly attached to the spring block, which fits between the brake arms and the frame or fork. The spring block has a concave surface to mate with the convex surface of the frame or fork. It does not rotate with the brake arms. These brakes can be centered only by bending the spring or repositioning the brake shoes.
