[DeTomaso] Stock rear calipers questions

MikeLDrew at aol.com MikeLDrew at aol.com
Thu Apr 24 04:11:20 EDT 2014


Guys,

I've been trying to figure out how the stock rear calipers work.   I 
haven't touched a set in years and I confess I've just given up trying to figure 
out their mechanics.

I understand that the piston must be rotated 45 degrees to unlock it before 
it is compressed to fit new pads; it is then rotated back into position.

But as to how the caliper actually works, I'm at a loss.

AJ has terrific photos here:

http://www.teampanteraracing.com/gallery2/v/asajay/pantera/brakes/rearbrakes
/

I'm used to the idea of a caliper that is open on the rotor side, and 
closed on the back side; I can wrap my brain around the idea of hydraulic 
pressure being applied to the back side of the piston, and being forced out of the 
caliper housing and thus acting on the back of the brake pad.

But the stock rear calipers are open on both sides.   I know there is a 
heavy steel housing that wraps around the calipers, so it's safe to assume that 
the side facing away from the rotor presses against this housing, which 
wraps around to the inside and acts on the back side of the inside pad.

I take it that brake pressure is introduced into the center of this 
chamber, and the two halves of the piston arrangement are forced outwards, away 
from one another?   One works directly against the back of the outer pad while 
the other works on the metal surrounding housing and transmits force to the 
other pad?

What I don't understand is the function of the parking brake system.   It 
appears that when the caliper is in the normal orientation, with the slot 
facing straight up-and-down, the two halves are locked together, and by 
rotating the piston 45 degrees, the threads unlock and the piston can be 
compressed.

What I don't get is how the piston then extends out of the caliper, if it 
is locked to the other side and pressure is trying to force them apart?   How 
does the piston move and compensate for pad wear?

Because I've never had a set of rear calipers apart in my hands, I'm just 
not getting it.   Anybody care to do some 'splainin'?

Mike (loves the simplicity of non-sliding four-piston fixed calipers!)
-------------- next part --------------
   Guys,
   I've been trying to figure out how the stock rear calipers work.  I
   haven't touched a set in years and I confess I've just given up trying
   to figure out their mechanics.
   I understand that the piston must be rotated 45 degrees to unlock it
   before it is compressed to fit new pads; it is then rotated back into
   position.
   But as to how the caliper actually works, I'm at a loss.
   AJ has terrific photos here:
   http://www.teampanteraracing.com/gallery2/v/asajay/pantera/brakes/rearb
   rakes/
   I'm used to the idea of a caliper that is open on the rotor side, and
   closed on the back side; I can wrap my brain around the idea of
   hydraulic pressure being applied to the back side of the piston, and
   being forced out of the caliper housing and thus acting on the back of
   the brake pad.
   But the stock rear calipers are open on both sides.  I know there is a
   heavy steel housing that wraps around the calipers, so it's safe to
   assume that the side facing away from the rotor presses against this
   housing, which wraps around to the inside and acts on the back side of
   the inside pad.
   I take it that brake pressure is introduced into the center of this
   chamber, and the two halves of the piston arrangement are forced
   outwards, away from one another?  One works directly against the back
   of the outer pad while the other works on the metal surrounding housing
   and transmits force to the other pad?
   What I don't understand is the function of the parking brake system.
   It appears that when the caliper is in the normal orientation, with the
   slot facing straight up-and-down, the two halves are locked together,
   and by rotating the piston 45 degrees, the threads unlock and the
   piston can be compressed.
   What I don't get is how the piston then extends out of the caliper, if
   it is locked to the other side and pressure is trying to force them
   apart?  How does the piston move and compensate for pad wear?
   Because I've never had a set of rear calipers apart in my hands, I'm
   just not getting it.  Anybody care to do some 'splainin'?
   Mike (loves the simplicity of non-sliding four-piston fixed calipers!)


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