Posted here where I'm more confident of an engineering debate than car forums where there seems little understanding or the ability to express an argument in words.
I have a Ford Cmax and amongst the web forums for this car it is acknowledged that the back disc brakes wear more quickly than the front ones. This appears to be caused by the caliper not releasing fully and there is always a silght drag on the rear wheel when jacked up. The handbrake does release fully and the cables are slack at the caliper so not related to the wear.
This has started me thinking about disc brakes in general. How do they release to give clearance for the disc once hydraulic pressure is removed? There is no return spring as there is in a drum brake. I can only think that a small amount of disc runout is desirable to push the pad away from the majority of the disc surface.
I'm changing pads soon so I almost wonder if it is worth using some shim stock to induce slight run out (still within spec) as an experiment.
Can anyone perhaps shed some light on this please?