Who says trigonometry doesn't pay!

[autobonrun]

Taking a break from my caliper rebuild job to design a template to measure the required 20 degree angle for the piston. Didn't have a protractor but I did remember enough trig to figure it out.

FYI. A triangular piece of cardboard 4 inches wide by 1 15/32 inches high gives you the 20 degree angle and fits well in the caliper.

Whoever did my brakes previously had the piston angles all screwed up. One piston was at the correct angle but the elevated portion of the piston was at the top. The other piston was no where close to 20 degrees. I assume both pistons should have the recessed portion at the bottom?

Other than brake squeal, is there anything else that having the piston at the wrong angle causes?

Thanks Wayne, the book made this somewhat easy. First time trying this, I had one caliper off and a new brake line on in less than an hour from starting. I need to buy a second book for the coffee table because I can see this one is going to get dirty.

[RoninLB]

Un-even pad wear. Don't know of many mech. who take that angle setting seriously. I do it, neuritically speaking.

[Roland Kunz]

Hello

The angle is important to prevent geting a turn impulse into the piston. This will generate souns, uneven waer and the piston will spin tearing the rubberprotectionboot into pieces.

Grüsse

[autobonrun]

Originally posted by Roland Kunz
Hello

The angle is important to prevent geting a turn impulse into the piston. This will generate souns, uneven waer and the piston will spin tearing the rubberprotectionboot into pieces.

Grüsse

Roland, your response explains why my the rubber boots were destroyed on my pistons. I thought it was just wear but the ones that were torn had the pistons installed at odd angles.

Historically, has Porsche always designed the pistons this way or was this something they learned later in the 911 evolution? I haven't checked other manufacturers; is this design used by all or specific to Porsche?