To avoid brake squeal, Bentley says the pistons should be oriented so that the chamfers on each piston form a 20 degree angle with the lower surface. I've read about this in this and other forums, including "the piston can be rotated with a needle nose pliers or a screwdriver tip...be careful not to tear the rubber dust cover/seal."

I am assuming the chamfered edge is the indented edge in the attached picture - correct?

I took a look at my right caliper that is being replacing. The chamfered edge went from 10:00 to 2:00 on the outer piston and 8:30 to 12:30 on the inner piston. I don't recall every having brake squeal.

Then I took a look at the new caliper. The chamfered edge on both the inner and outer piston goes from 10:00 to 2:00.

So how important is it to orient this at 20 degrees (or from ~5:00 to ~9:00) for the chamfered edge for both inner and outer pistons. Looking at the brake pad shim and the caliper, I could not see how this would do anything.

And something I have not seen mentioned - is the 20 degrees relative to the back of the caliper where the pads get inserted, or relative to the front of the caliper?

Not sure how to show the image, but it is here:

http://www.brickboard.com/IMAGELIB/index.htm?uid=31749&pix_type=TECHNICAL&js_link=1