I need assistance in identifying the unidentified callipers on my 1983 e24 (late model) so that I may obtain the appropriate pistons.

[DolSquirrel]

Hello everyone, I am reaching out from the bigcoupe community in a last attempt to get assistance in identifying these brake callipers. They can be directly attached to my 1983 633 csi, but they are certainly not the original callipers since the size of the pistons is different. Additionally, the brake callipers used in the e28 model have identical component numbers.

I am currently in the process of rebuilding the callipers for my restoration project. Unfortunately, I mistakenly discarded the old calliper pistons and the new ones I purchased do not fit properly due to their larger size. I have searched online for suitable replacements specifically designed for the 633 model, but all available options are also too big. I am aware that I should not have disposed of the old parts, as I usually do not make such errors, but this was an accidental oversight on my part.

The calliper lacks a part number and instead displays "BMW 57/25" on one side and "BMW ATE" on the other. The only web information I came across pertained to the e46s, maybe. However, all of those options have a larger or same calliper bore size. I am certain that if my bore size is 57mm, I cannot use a 57mm piston since there has to be some clearance.

The bore measurement indicates an internal diameter (ID) of 57mm. Therefore, would it be correct to assume that I need pistons with a diameter of 56mm? Which specific BMW calliper is compatible with my e24 and can be easily installed? The primary enigma that stumped everyone was the e24 gang.

I am now facing a challenge in the restoration process as I am unable to determine the appropriate size of pistons required. Furthermore, I am reluctant to get other callipers as I have already meticulously prepared and painted these callipers, and have also obtained new seal kits and other necessary components. Currently, I am quite intrigued in the potential dimensions of these objects.

If anybody has any suggestions, please inform me. I reached out to ATE, but they were unsuccessful. I also contacted other brake supplier businesses, and they all confirmed that higher size pistons are required for the factory e24 (and e28) brakes.

[w4rlock]

Have you attempted to explore this location...

https://www.realoem.com/bmw/enUS/showparts?id=5274-USA-06-1983-E24-BMW-633CSi&diagId=34_0451

[DolSquirrel]

What is the utility of realoem if it does not provide a component number? Furthermore, realoem does not provide information on the sizes of calliper pistons. As I said before, these callipers are not the standard e24 callipers, hence the brake diagrams on realoem.com are not useful.

[w4rlock]

[w4rlock]

It would have been better to avoid the inconvenience and purchase appropriate components instead.

[DolSquirrel]

As previously mentioned, the component number obtained from realoem corresponds to a brake calliper specifically designed for a 633csi. The brake callipers installed are not the regular e24 brake callipers. Therefore, the component number, which only refers to the seal kit and not the actual piston, is of no value to me since these callipers are not the original e24 callipers.

[HeadlinesQuick]

A simple Google search will provide hundreds of results.

[w4rlock]

Consider bringing the aftermarket caliper/piston to a BMW dealership...