Ferrari Mailing List: Re: confused over adjustmenmt or 308 rear brakes..

[robert_h_bowser [at] juno.com (robert_h_bowser]

It is a weird setup....

Doing this from memory (from ten years ago...).   The allen screw is a male 
screw that reaches into a star-shaped fitting that fits into the back side of 
the piston.  Basically, it consists of a female threaded plug with a spring 
steel outer section that snaps into a grove inside the piston.  So the inner 
threaded plug can move back and forth a millimeter or so with respect to the 
piston.  So you screw it down until the range of motion allowed is within the 
range of motion required for the brakes to work.  If you screw the piston down 
too far, the rear brakes bind (not good).  Too little, and the rear brake 
piston can't move far enough to engage the rotor, so the rear brakes don't work.

I gave up long ago trying to do the 0.1mm adjustment with a feeler gauge.  As 
the pads/rotors wear and get grooved, it is impossible to use a feeler gauge to 
get the right clearance.  I just screw the piston down until it bottoms against 
the rotor, then back it off about a quarter turn.  As the brake pads wear, the 
brake pedal starts going further and further down towards the floor.  Adjusting 
it brings the pedal back up to the original position.  Seems like I need to do 
that every 500 miles or so.

When I first bought my 308, I rebuilt the brakes.  Front calipers were a snap.  
I tried to take apart the rear calipers.  Not knowing how it all fit together, 
I tried to pry out the pistons.  Thought they were just stuck in the bore.  
Finally did pry one out, and realized how they fit together.  Felt like an 
idiot.  All you need to do to get the piston out is use the allen screw to push 
the piston out.

Bob
'78 308GTS
'01 Corvette Z06

-- Gavin Bedggood <gavinnz [at] xtra.co.nz> wrote:
Ok, thanks for the advice on the brakes, it's very helpfull.
   
  Just one thing I have spend a few days trying to get my head around and 
failed.... the plug on the face of the caliper that faces in towards the centre 
of the car... you take that out and inside is a fastening that an allen key 
fits into.... that when I wind it back and fourth the piston moves.... both in 
and out.
   
  I have read you need to adjust the clearnace from pad to disc to 0.1mm using 
that fastening...
   
  BUT... what I cant get my head arund is how does that fitting adjust the 
position of the piston AND STILL LET THE PISTON MOVE when you apply the 
brakes????
   
  HELP!  My brain is MELTING!!!!!!
   
  Gavin
  New Zealand
  '78 308... jacked up with back wheels off.
   
   
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