Well, they don't do any work at road speeds ( rmember virtually all our cars are frontwheel drive with load proportioning valves to limit rear brakeline pressure, so I don't see the need. Also the handbrake mechanisms are a real pain. Every rear caliper I had to change on the VW worked perfectly as a hydraulic device.... except that the mechanical handbrake mechanism would fail, therefore a certain fail on the UK annual roadworthiness test (MOT test). That was a Girling design that is used on LOTs of European cars. The separate mini drum for the hanbrake used by Porsche is OK, but if you are as mean as me, that makes disc replacement horrendously expensive!
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