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I was replacing a tyre a couple of days ago, and noticed my rear axle had snapped.

So I replaced the axle, just a normal road 10mm x 145mm, it's a basic Shimano sprocket set and no-name aluminium rear hub.

I fitted the new axle, with new bearings and plenty of grease, that all seemed fine.

On the bike though, the wheel is not straight. Oddly it seems to come from the sprocket side of the rear hub. I would say the axle oscillates within the hub, as the wheel turns. This is probably best explained with a video. The oscillations occur once per revolution.

Things I've checked... * That I've not put too many bearings in either side. * That the hub, where the bearings sit, is not damaged. I think it's OK, though it's hard to see.

Things I think it might be, but not sure... * Have I bent the hub? Not sure if that's even possible. * Some other deformation in the hub.

Sprockets

Freewheel

Update

Thanks to Andrew Henle and Noah Sutherland for the comments, both really helpful. So, I took off the freewheel and checked the number of bearings.

Taking off the freewheel and a rubber grommet meant I could get a much better look at what was happening. From this, I think the hub itself is distorted, but I'm not sure really. There was some damage to the part of the hub where the bearings sit, but just really small scratches. You can see the uneven movement in the short video below.

At this point, I think I need a new hub. I guess the impact that snapped the axle also distorted the hub.

Keen to hear if anyone else has further thoughts on this though.

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    Did you put enough ball bearings in the bearing race? It looks like there might not be enough bearings, allowing the axle to move off center as gaps grow as the bearings move about while the wheel rotates. How many did you put in? Can you compare the new axle with the old one? Is the bearing surface the same size/diameter?
    – Andrew Henle
    Feb 26, 2019 at 11:49
  • Thanks Andrew. Yea, I think so, but I'll check again.
    – AndyGaskell
    Feb 26, 2019 at 12:22
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    I would take the freewheel off and see how the axle works with just the hub. Also, that looks like an awful lot of axle sticking out past the lock nut. Are you missing a spacer? Not that that would affect this problem though.
    – Noah Sutherland
    Feb 26, 2019 at 16:28
  • Thanks Noah, I'll try with the freewheel off, just got myself a freewheel tool today.
    – AndyGaskell
    Feb 27, 2019 at 0:01
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    @DanielRHicks if you say so. my 40 year old Campy Super Record hub is a bit tighter than a single ball space.
    – Stanley Pawlukiewicz
    Mar 4, 2019 at 18:00

1 Answer 1

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Very common on freewheel hubs. The gears extend beyond the bearing which puts a lot of stress on the drive side. With a casstte this is not the case. Personally I would upgrade.

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    Yeah, on looking at the video again I would guess that the hub is bent somehow.
    – Daniel R Hicks
    Jul 3, 2019 at 12:02
  • Aye, I figured in the end the hub was twisted or warped somehow. It seemed unlikely that suck a large chunk of aluminium would deform, but kind of ruled out all other possibilities really.
    – AndyGaskell
    Jul 14, 2019 at 11:01

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