the piston on the rear caliper is on a thread. the piston must be wound back in on the thread. there is a special tool available for this, but, with a little patience you can do this job without the special tool. you will need a set of mole grips and a set of swan neck pliers ( water pump pliers ). using the swan necks, apply moderate force on the face of the piston whilst simultaneously turning the piston in a clockwise direction using the mole grips. CAUTION.. do not clamp the molegrips onto the rubber dust shield as you will tear it. do not apply too much pressure with the swan necks as you could cause internal damage to the caliper. NEVER try to force the piston back without rotating it, you WILL f**k it up. hope this helps
tony j
August 2007