Brake piston orientation

[Scott R]

I'm getting around to sorting out a big box of parts I aquired and I was going to rebuild these calipers, but I believe the pistons are 180 deg off. Anyone know by looking at the picture? They should be clocked the other direction at 20 deg I think.

[SCOTITUDE]

looks right

[Scott R]

OK, I flipped the caliper and put the tool in according to what I believe the picture means.

[aston@ultrasw.c]

I don't have a caliper in front of me but....

Decide if the caliper is intended for the left or right. Orient the caliper as it would be mounted with the bleed screw at the top. Now insert the tool.

Imagine that the rotation arrow in the diagram intersects with the cutout at approx 90 deg.

If you are still not sure print the diag and tape it to the fender where you are working. On the passenger side the ink will be on the outside. On the driver side the ink will be on the inside.

[Scott R]

Originally Posted by aston@ultrasw.c

I don't have a caliper in front of me but....

Decide if the caliper is intended for the left or right. Orient the caliper as it would be mounted with the bleed screw at the top. Now insert the tool.

Imagine that the rotation arrow in the diagram intersects with the cutout at approx 90 deg.

If you are still not sure print the diag and tape it to the fender where you are working. On the passenger side the ink will be on the outside. On the driver side the ink will be on the inside.

Thanks for that tip, I'll give that a try this weekend.

[aston@ultrasw.c]

Originally Posted by Scott R

Thanks for that tip, I'll give that a try this weekend.

I'm glad that made some sense

[djdsc]

Originally Posted by aston@ultrasw.c

I don't have a caliper in front of me but....

Decide if the caliper is intended for the left or right. Orient the caliper as it would be mounted with the bleed screw at the top. Now insert the tool.

Imagine that the rotation arrow in the diagram intersects with the cutout at approx 90 deg.

If you are still not sure print the diag and tape it to the fender where you are working. On the passenger side the ink will be on the outside. On the driver side the ink will be on the inside.

Yes do this!!!

[Scott R]

Is that from the FSM? That's perfect! Thank you both!

[CCM911]

If you look closely in the Bentley manual, you can see where the piston orients. I have been doing mine by eye for the past ten years(numerous track days led to many rebuilds) and have never had any issues.

[McLovin]

I've always done that, but never known the purpose!

Why does it matter?

[CCM911]

The argument is that as the pads close in, the rotation of the disc will try to angle the pads, as opposed to having them lie flat against the rotor as the pistons push the pads.

I am sure there is an expert out there that can explain this better than I.

Bill Verberg, are you out there?

[JJ 911SC]

If off the 20 degree line, they would squeal like little piglet...