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The calipers fitted to the rear of the ur-quattro - except the very early two-part caliper - are self-adjusting. It is necessary to assemble and fit them in a specific way in order to have a fully functional handbrake - the process is not intuitive.
Diagram 1 - handbrake OFF - as shipped by the factory for fitting to a disc and pads with a nominal thickness of 44mm. The handbrake lever must not be operated until the caliper is fitted and bled. It is best to loosen the handbrake adjustment (centre of vehicle, above propellor shaft - deep 10mm socket and long extension) and not refit the handbrake cable until the footbrake has been pressed 5 to 10 times after bleeding.
Diagram 2 - handbrake ON - if the caliper is correctly fitted, the handbrake should be fully functional. However, if the factory settings are wrong or the caliper has been fitted to an old disc or pads, it is possible that the piston will remain out and the handbrake will not work.
Diagram 3 - handbrake OFF - there is play between the piston and the pads and a handbrake solution will not be achieved.
Diagram 4 - handbrake OFF - measure the total thickness of the disc and pads (e.g., 39mm) and add 1mm to permit fitting. The piston must be rotated to adjust it - 90° is approximately 1mm - and set in this example to 40mm.
Diagram 5 - handbrake ON - this is now correctly adjusted, similar to Diagram 1, but for the example disc and pad thinkness of 39mm.
If fitting new discs and/or pads to this type of caliper, the same adjustments must be performed. See the article on renovating calipers for general hints and tips.