Front Caliper Piston Retaining Clip

[72S#1711]

Are these gizmo's really necessary?
I reassembled one side without them to give it a test and everything seems to work fine.
Are there long term considerations I need to be aware of?
My early S's pistons are relieved on leading edge and do not run these things.

Any advise would be greatly appreciated.
Thanks

[Dave at Pelican Parts]

Those are to keep the stock caliper piston orientation, so the pistons do not rotate. There is some asymmetry about the piston, which is supposed to combat taper wear in the pads.

The S calipers may not have those--I don't really know. The 911 board might, or Eric at PMB Performance would certainly know.

--DD

[72S#1711]

Thanks for the quick response Dave,

I'll dig a bit deeper and see what I can learn.

Cheers

[TheCabinetmaker]

They are anti-rotation clips, I Bought a 914 that had front brake pads that were worn crooked, leading edge worn down considerably more than trailing edge (or visa versa, I forget which now)) I found the prior owner had omitted the anti-rotation clip and the pistons did indeed rotate out of specification. (piston rotation orientation is specified in the repair manuals)
the piston is NOT symmetrical, and is designed to apply the pad to the rotor in a slightly uneven fashion to compensate for the fact that the pad is pulled un-evenly on the rotor as it makes contact, simply because the rotor is spinning in one direction nearly always (except when backing up, which is done at low speed)
One pad had near a 1/4 inch difference in trailing edge verse leading edge, very significant!!!

I would certainly install the anti-rotation clip, it is needed, it is there for that reason, to assure uniform pad contact.

How long before your pistons rotate out of spec I don't know, It varies as each pad on the afore mentioned car was worn differently, some pistons rotated more than others when the clip was not installed.

Get them clips installed!!!!