[Shop-talk] Why in the world do we need 'spinning' brake pistons?

[John Miller]

On 9/13/2018 4:16 PM, Brian Kemp wrote:
> I'm told it is how the parking brake adjusts itself when the pads get 
> worn.  The parking brake lever pulls a cable which actuates the rear 
> brake calipers.  Discovered the special tool after battling the rear 
> brakes on my wife's Jetta.  I borrowed the special tool from the local 
> O'Reilly or Pep Boys.

You have three basic approaches out there for a parking brake with rear 
discs.  One (common in higher-end German products, trucks, and a few 
others) is to put a drum in the hat of the rear rotor.

One (found generally on high-end products - Italian exotics, high-end 
Jags, Tesla Model S/X) and some aftermarket kits) is a separate 
mechanically-actuated parking-brake caliper.

The third and by far most common is to put a screw-jack mechanism inside 
the rear caliper piston.

This is where the retraction tool comes in, and yeah, it's a PITA that 
they're all different.

John.