What size are the nuts holding the front wheel?

  • I am trying to install a front wheel on a bike - the axle of the wheel is threaded, but I'm having trouble finding out what size thread it is, and what nut can go on this. The size of the thread on the axle is the same as an 8 mm screw, but a standard M8 nut (with 13 mm hex) does not fit on it. Do bikes have some special kind of nut there?

    If I look at the thread, and at a standard M8 screw, the thread on the bike axle is a bit more dense then on the screw, but I am not aware of existence of two kinds of M8 nuts, so far every M8 nut I've seen fits every M8 screw.

    For those coming here looking for a wrench size for the bolt, it's probably 15 mm.

    It depends on the bike. Most bikes bought in a bike shop made by any large brand use mm, but some cheaper bikes purchased at big box stores use american or non standard bolt sizes. Even on bikes that use the metric system, 5mm bolts are very common, so are 8mm and even smaller ones.

    Simplest thing to do is to take the wheel (or just the other nut) to a hardware store and have them find a match in their bins.

    I was looking for the same. Took wheel with axle to hardware store, but nothing matched up with the threads. It appears to be extra fine thread. If I used what they had, I would've had to force the nut onto the threaded hub shaft and it would've been ruined. I'm going to have to go to a specialty fastener shop or contact the manufacturer representative, if possible. Seems odd that they

  • There's a wide variety of axle diameters and threading.

    There is a spiffy table here: list of common bicycle thread sizes from Park Tool.


    Edit: while it's probably too much to include the whole table, the ø8mm sizes are reproduced below.

    8mm x 1mm Square-type crank bolts, front solid axle hubs, suspension system hardware

    8mm x 1.25mm Stem hardware, stud type crank nuts, suspension hardware

    8mm x 0.75mm Chainring bolt

    FWIW 8x1.25 is the (coarse) default for M8, but 8x1 and even 8x0.75 are allowed as the "fine" pitches by ISO 262.

    So, 8x1 isn't exclusive to bike use or non-standard, it's just less common.

    Thanks, so it seems like bike axle thread has a pitch of 1 mm, while a standard M8 screw/nut has a pitch 1.25 mm.

    the link appears to be broken

    Answers should include answers, not just links.

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Content dated before 6/26/2020 9:53 AM