Why do rear calipers often need winding back?

[a7x88]

As above really. It always seems to be just the rears..... How come? What purpose does it serve?

[E-bmw]

It is because of the different way they operate, as in they have dual operating modes handbrake & footbrake, both put a force on the pads in a completely differently way.

[VAGslag]

It's because they have self adjusting hand brakes...

[Pupp]

Always been intrigued by how the mech works... they need to be wound back in but extend out linearly... The pistons are not threaded are they?

[S0 What]

Pupp said:

Always been intrigued by how the mech works... they need to be wound back in but extend out linearly... The pistons are not threaded are they?

The adjster inside is threaded, as the piston moves out the adjuster turns, to unadjust as you can't reach the adjuster you turn the piston, the pressure the tool puts on the caliper holds the threaded adjuster still allowing the caliper to wind around it and go back into the caliper body.
Have alook below at a typical rear caliper

https://www.2carpros.com/forum/automotive_pictures...