20 Degree Caliper Piston Setting Tool

jmackro

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So I’m doing a rear break job on the Bav and saw these 20 degree cut outs on the pistons. What is the point to it?
The point of the cut out is to tilt the brake pad into the rotor, which prevents it from vibrating. Or maybe it tilts it away from the rotor. Anyhow, it is important to install these pistons correctly, though I suspect that 19° or 21° would work equally well.
 

Jon B

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Here's an illustration from the Porsche manual...

DSCN3047.JPG

The intent is for the caliper piston to apply less pressure to the leading edge of the brake pad, so that the friction material will wear evenly.
 

E3_UK

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Here's an illustration from the Porsche manual...

View attachment 118435

The intent is for the caliper piston to apply less pressure to the leading edge of the brake pad, so that the friction material will wear evenly.
Any idea if the Porsche caliper is the same ATE part as BMW ?. Joking aside I would like to buy the tool rather than mess around with bits of paper.
 

Jon B

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Any idea if the Porsche caliper is the same ATE part as BMW ?. Joking aside I would like to buy the tool rather than mess around with bits of paper.
I'm not aware of any Porsche calipers being the same as those on your E3.
Even so, the 20° piston angle was the same, and the tool from Buttys Bits should work well on your BMW too.
 
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