Brake piston gauge

Christopher

Christopher

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The blue books say that the angle of the piston should be checked to ensure a 20 degree setting when replacing the rear brake pads, with a brake piston gauge

http://www.e9-driven.com/Public/Library/BMW-E9-Manual/pages/en/34212010.html#refertoc

a/ - where can i get a gauge (i can't source one via an internet search)
b/ - how likely is it that the pistons have moved during removal of pads
c/ - how necessary is this to do anyway ?

Any guidance appreciated
 
Christopher said:
The blue books say that the angle of the piston should be checked to ensure a 20 degree setting when replacing the rear brake pads, with a brake piston gauge

http://www.e9-driven.com/Public/Library/BMW-E9-Manual/pages/en/34212010.html#refertoc

a/ - where can i get a gauge (i can't source one via an internet search)
b/ - how likely is it that the pistons have moved during removal of pads
c/ - how necessary is this to do anyway ?

Any guidance appreciated
Click to expand...

yes
i did a gauge for my car from a piece of thin plywood (4mm)
i have not checked this yet, but i am prepared to
i think that if the book says to do it, ....you'd better do it
 
a/ - make one
b/ - fairly likely that they have rotated
c/ - only if you want quiet brakes
 
What are we trying to do?

Is this all about rotating the piston until it reaches a certain point? I tried to understand the description via the link but I think I am missing the point. Is there a mark on the piston that has to face a certain position, the book said something about the 20 must be adjacent to the point where the piston enters the fixed caliper. I do not understand this, can anyone help?
If the above is correct, then what are we trying to do, are the pistons formed to a special shape?
I ask as I am not happy with my brakes and plan to dismantle again soon.
Thanks
C
 
There is a raised semi circle on the piston (see pic), the bisecting line is supposed to be 20 degrees off of center or something. I took pictures and just estimated the way it was before it came out. No problems.

photo.JPG


Cornishman said:
Is this all about rotating the piston until it reaches a certain point? I tried to understand the description via the link but I think I am missing the point. Is there a mark on the piston that has to face a certain position, the book said something about the 20 must be adjacent to the point where the piston enters the fixed caliper. I do not understand this, can anyone help?
If the above is correct, then what are we trying to do, are the pistons formed to a special shape?
I ask as I am not happy with my brakes and plan to dismantle again soon.
Thanks
C
Click to expand...
 
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