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Discussion Starter #1 (Edited)
Hello All,

I recently rebuilt my brake calipers, and yes, you can get them from Rockauto or send them into PMB to be rebuilt easy enough, but I wanted to do it myself.

One part that was a challenge was getting the caliper piston positions correct. Translation, I got it wrong, put them on the car and had to take them off to get it right! :grin2:

I used the old IAP page that had the templates. I cut the templates out and glued them to cardboard so that they could be handled easily.

View attachment Caliper Piston Position templet (1).pdf

I also found this diagram which "helped"

caliper_piston_alignment.gif

I never say that I am the brightest one, but after reading the "directions" I thought I got it right. Wrong!!!!

It wasn't until I saw this, that it hit me on the correct positioning of the pistons, Front and Back, Left and Right. Each piston is different from the other, even if they are on the same side of the vehicle (my initial thoughts).

Caliper Piston Orientation.jpg

Here is a picture of the pistons. You can see the raised edge and the gap in between. ATE designed the raised edge to help with even wear of the brake pads. The gap is to face the direction of the brake rotor turning.

Front Pistons Raised Edge.JPG
 

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Discussion Starter #2 (Edited)
So I made up this chart that shows the in car position of each caliper piston.

Summary.JPG

And here are some pictures of the calipers and the templates, setting the piston positions.

Left Front
Left Front.jpg

Right Front
Right Front.JPG

Left Rear
Left Rear.JPG

Right Rear
Right Rear.JPG

All calipers have 2 pistons. The other piston is to be set with the mirror image of the one shown above. Basically, use the other side of the template.

Hope this helps someone getting it right the first time.

Vin
 

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Agree! I FINALLY figured it out for my brain - the "open' end faces the leading edge, and the big side of the 20 degree tool goes INWARD . If ya line up the inside 'edge' with the center of the wheel you are good to go. Took me about 8 brake jobs to figure it out; it was very confusing to me.
 

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Discussion Starter #4
Agree! I FINALLY figured it out for my brain - the "open' end faces the leading edge, and the big side of the 20 degree tool goes INWARD . If ya line up the inside 'edge' with the center of the wheel you are good to go. Took me about 8 brake jobs to figure it out; it was very confusing to me.
Thanks for that!

I have to admit, I was getting confused and the more I thought about it, the worse it got! :wink2:

I literally got the Left Front correct and the other 3 wrong!

Glad I am not the only one out there.

Vin
 

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and both sides of the same caliper are mirror imaged --- inside piston and outside piston have same orientation ; mirror imaged. That too took me while and like you, I'd set the thing, then doubt would creep in, I'd go check it and lo and behold it was not correct 75% of the time (the other 25 was the 1 in 4 chance to get it right based on spacial orientation!
 

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if you think about it, that's ridiculous !!! im grinding them flat like every other caliper piston on the planet !!!
 

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im grinding them flat like every other caliper piston on the planet !!!
I always thought this whole business of getting the piston orientation correct was unique to my Alfa Spider. Just the other week I learned that Mercedes W123 have the exact same set up!

A bit embarrassing, as I own a W123 as well. I will say to my defence that I do much more mileage in the Spider. Whereas I can take the callipers of my Spider blindfolded by now, I have not yet ever had to do any brake jobs on the W123!

Jeroen
 

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This is out of the Alfa Romeo ATE brake manual from the mid 60's.
 

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according to the ATE Bremsenhandbuch (389059008X) , the 20° set up is designed to hinder uneven wear of the pads.
 
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