Need advice with original (?) brakes!
 

Hi everyone,I'm starting to work on my C3 and have two questions:1) I removed my Calipers front and rear.The rear rotor inner wall is thiner than the outer (7mm vs 9mm) which is, I think a huge difference. The Rear rotor is also riveted, So does that mean I need to replace the entire rear rotor?2) I separeted the calipers (delco moraine) . Rear piston diameter is 1 7/8" and front piston is 1 5/16". Are those standard sizes and should they be different? I was reading that I should replace them with O-ring pistons --- any suggestions on how to proceed?
Thank you in advance.

https://cimg8.ibsrv.net/gimg/www.cor...c7d02a0a9.jpeg
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https://cimg9.ibsrv.net/gimg/www.cor...819db988c.jpeg
https://cimg0.ibsrv.net/gimg/www.cor...ce8686170.jpeg
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I just rebuilt my calipers last month. They are SS sleeved I installed in about 1984. I like these guy's parts and they have pretty good tech advice. I'm not sure what the rules are about posting links to non-supporting vendors web sites so someone let me know if it's not allowed. At any rate, I'm sure this will start a good conversation.
Cheers
https://www.duntovmotors.com/tech-calipers.php