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My freehub body is totally stuck

The only way to turn it at the moment is with a whip chain and a cassette on.

I cleaned it with WD40, but that didn't help at all.

Also I tried to "hammer" it down with the cassette, just veeery gently, because I don't want to damage the cassette. But nothing.

There where balls in the freehub body that I removed not to lose them.

Any suggestions ? Should I use pure force ?

enter image description here

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Edit:

Cloud open it with a hexagonal wrench, 12mm. (opening is anticlockwise) Thank @olliebulle for the suggestion. enter image description here

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Just to be clear, the part shown on your pictures is called a freehub body (black cylinder with splines). It incorporates the ratchet system enabling the hub to engage one way and to disengage the other way. This is where you attach the cassette. A freewheel, on the other hand, is a single part that combines the ratchet system and the sprockets. (I edited your question to update the wording)

A freehub body can definitely need to be replaced if the internal bearings are gripped or show excessive loose. You would need to use an hexagonal/Allen wrench of the correct size (e.g. 10 mm) to unscrew the fixing bolt in the middle to remove it. One good way if it is stuck is to clamp the hex wrench in a vise and put your freehub body over it. You will have a way longer lever (turning the wheel instead of turning the wrench) to help you. Make sure to inspect the threads for damage and put grease before installing another one.

You could also try to service the freehub body yourself if you want to reuse it. This is not a procedure one would normally do as freehub bodies of the kind you have are not supposed to be opened but it is doable. See this video for a demonstration.

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  • Thanks a lot! Any suggestions how to find out what kind of freehub body, I've got ? I will definitely buy a new one. And does it look like 11 mm to you or is that like a standard size ?
    – Schwenk
    Feb 26 at 14:18
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    Freehub bodies are notoriously hard to determine what you have, and, thus what you need for replacement until they are removed. While the outside, splined part is standardized (for the number of gears on a cassette its designed to carry), the hidden, inner aspect differs between manufacturers. The differences are based on how the body is attached to the hub and the location and number of pawls. Unless the hub model and manufacturer is known, and enough of them has come to market where there may be references available--only disassembly will shed light on the replacement need.
    – Jeff
    Feb 26 at 15:09
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    @Schwenk it could be 11mm. However a 10mm is a common size for that application. In fact, my bike tool kit has a specific 10mm Allen (hexagonal) wrench that mates up to a 3/8-inch ratchet (or torque) wrench just for that type of application. I would put a small wager that it is 10mm.
    – Ted Hohl
    Feb 26 at 18:16
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    10mm is likely, but freehub bodies also are a place where weird sizes lurk. It could be 11 or 12mm or some weird imperial size too. Since the freehub body itself is also unique, OP might be best taking it to a LBS and getting it replaced there. Clean it first, mechanics love that.
    – Criggie ♦
    Feb 26 at 18:42

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