Caliper Piston Sizes/Compatibility

[Nate37]

I took apart the brakes on my 318is to rebuild the calipers and get the calipers sandblasted and re-plated. Unfortunately the sandblasting shop lost my pistons, so now I have beautiful caliper housings with nothing to put in them. I did a bit of searching on this, but nothing turned up: are the caliper piston sizes the same across all the E30 disc brakes? This page made it sound like the rears are interchangeable, but in the front it may matter whether the caliper was made by Girling or ATE: https://www.e30zone.net/e30wiki/inde...rakes#Calipers My car has Girling calipers in the front. Does anyone know for sure if they are the same?

Basically, I'm wondering if these will fit, even though they say they are for ATE calipers and do not list the 318is as a compatible model:

https://www.bimmerworld.com/Brakes/Caliper-Parts/Stainless-Steel-Brake-Caliper-Piston-Set-Ate12.html

https://www.bimmerworld.com/Stainless-Steel-Brake-Caliper-Piston-Set-Ate13.html

If neither of those will work, where else can I source them? Hoping to buy just the pistons without having to go buy 4 whole calipers from a scrap yard...

[Vincenze]

The rear brakes are all ATE.

There are remanufactured Girling brake calipers on eBay, etc for $40.

[fitswell]

the issue with reman calipers is that they will arrive without the protective zinc coating, especially if you go for the budget version. they will rust up and look like poo in no time at all.

[Nate37]

Thanks guys. Been meaning to write this up in my build thread, but I ended up sourcing new pistons on eBay and using my old calipers. I bought them from Frentech UK - would highly recommend if anyone ever needs new pistons. They were very responsive and even created a new item on their eBay store with only the parts I needed to order. Here's their store: https://www.ebay.com/usr/frentech-uk?_trksid=p2047675.l2559