[s-cars] Big Red (blacks) ?

[bob.rossato at att.net]

Are you using the Black 928 GTS calipers?  If so, did you swap the bleeder
lines around?  If not then, assuming that you installed the calipers such
that the bleeder valves are pointing upwards, you ended up with the pistons
lined up in the wrong rotational orientation and that is your problem.  The
smaller piston is supposed to be the leading one (with regard to a point on
the rotor surface entering the caliper) and the larger one is trailing.  So,
in the orientation that the calipers mount on our cars the smaller piston is
supposed to be at the top.

The reason for the difference in diameters is that as the first piston acts
on the pad/rotor some small amount of pad material is carried away which acts
to spread the downstream area of the pad away from the rotor.  In order to
compensate for this and end up with equal pad wear the second piston needs to
be larger.  With the caliper mounted backwards you will end up with the wedge
shape wear on your pads.

If you are using the 993TT Big Reds, which don't need to have the lines
swapped, then ignore the above.

Bob

> --
> [ Picked text/plain from multipart/alternative ]
> Hi all,
>  While switching to the Porsche drilled rotors today I noticed that on both
> calipers the top of the pads were almost gone and the bottom was barley used. I
> pulled the pads out and recessed the pistons. All four of them moved freely
> and seemed to be fine. I bled them all and put new pads in. Anyone had this
> happen? Any Ideas what caused it? Thanks,
>
> Elijah
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