Welcome to our Ask a Mechanic column where our expert mechanic Daniel Slusser answers your bike maintenance questions. If you have a question for Daniel, please post it on our Facebook Wall or e-mail Daniel directly at firstname.lastname@example.org.
Question: I have a hybrid with disc brakes on quick release wheels. When replacing the wheel after a puncture it is very hard to center it. The disc rubs on one or other of the brake pads. Is there a quick fix for this? From: Steve
Answer: Your hubs likely have a threaded axle fitted with locknuts at either end. The face of the locknut on the end of the axle is never perfectly perpendicular to the axle. This means that the orientation of the axle (i.e. rotation) when it is inserted into the frame or fork dropouts will affect your disc alignment within the caliper.
But before I explain the fix for this, you need to ensure that your hub is properly adjusted and that the lock nut is tightened down on the bearing cone. If your wheels are wobbly or the axle locknut is loose, the bearing adjustment is altered every time the wheel is taken in and out of the dropouts, so you need to fix this problem first, if you have it.
Now that your hubs are properly adjusted and the locknuts are nice and tight, we are ready for the remarkably simple fix. Use a silver Sharpie or a paint pen to mark the axle while it is installed in the dropouts with the caliper adjusted so that the disc doesn’t rub on the brake pads. Make a corresponding mark on the dropout that you line up with the axle every time you install the wheel in the dropout. Admittedly this is a bit of a hassle, but it should cure your problem.
Daniel Slusser is a professional bicycle mechanic with over ten years of experience. He holds a bachelor’s degree in business administration from HSU and a master’s degree in history from Cal Poly. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.