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I want assistance in identifying the unidentified callipers on my 1983 e24 (late model) in order to get the appropriate pistons.


Grundysp

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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 mounted into my 1983 633 csi, but they are certainly not the original callipers, since the size of the pistons is different. Interestingly, 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 the options available 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 does not have a specific component number. It is just labelled as "BMW 57/25" on one side and "BMW ATE" on the other. The only information I discovered online pertained to the e46s, maybe. However, all of those options have a larger or the same calliper bore size. I am certain that I cannot use a 57mm piston if my bore size is also 57mm, 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 alternative callipers, since I have already invested effort in preparing and painting them meticulously, and have also obtained new seal kits and related 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 unable to assist. I also contacted other brake supplier businesses, all of whom confirmed that higher size pistons are required for the standard e24 (and e28) brakes.

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What is the utility of RealOEM if it does not provide a part number? Furthermore, realoem does not provide information on the sizes of calliper pistons. As I said before, the callipers I have are not the standard e24 callipers. Therefore, realoem does not provide any useful braking diagrams for them.

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As previously mentioned, the component number obtained from realoem corresponds to a brake calliper specifically designed for a 633csi model. 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 not helpful to me since these callipers are not the original e24 callipers.

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