My colleague at work ran into an unexpected result when he tried to push the piston into the caliper on the rear disc brakes. The c-clamp method that worked great on the front calipers failed miserably on the back set.
My research on the Internet showed that the pistons on these type brakes must be rotated while they are being pushed in, and there is a special tool for the job.
My question is why do the pistons have to be rotated? What physical/mechanical feature makes this necessary?