Issue replacing Avid BB7 disc brake pads
If only one brake pad rubs and there is a gap between the rotor and the other pad, then your brake isn't centered well. To fix it:


Use an allen key to loosen the caliper so that you can slide it around but it is still attached.
Pull the brake lever. This way, the brake goes into a position centered around the disc.
While still holding the lever, secure the brake again.
Release the brake lever and find out that your brake doesn't rub any more!