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My rear fixed-gear wheel seized up yesterday on my commute home. I suspect it's the result of my bone-headed adjustment after replacing a broken locknut on the axle (I may not have put the new locknut on tight enough). The wheel now refuses to turn - the axle is bound.

I'm curious though: what has actually happened inside? I noticed it happen over one or two revolutions, as if something was wrapping around the wheel. Could it be that a bearing cage came loose and wrapped around the axle somehow? I've tried to take it apart and see, but though I got the locknuts off, I've nearly rounded off the cones themselves (and ruined a cone wrench) trying to get them unscrewed.

Thanks!

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  • the bearing cage is rather rigid, however the bearing balls may have grouped and shifted and then scored the surfaces
    – ratchet freak
    Feb 14, 2014 at 13:08
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    The fact that the cones are so tight suggests that the cones have been screwed together by the wheel motion, due to a loose locknut. In effect you were using a wrench with a 13-inch-long handle. (Probably best to take it to a bike shop. They will probably have replacement cones (and a new cone wrench)).
    – Daniel R Hicks
    Feb 14, 2014 at 19:12

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It is rare for a bike bearing to suddenly seize. Even a bearing "run dry" or exposed to saltwater or whatever will generally just get rough and squeaky.

In order to seize you generally have one of two things:

  1. (Rare) A fragment of something -- sand, a sliver of metal, etc -- gets in between the balls in the bearing, causing them to lock.
  2. (Common) The failure to properly fasten a lock nut or other fastener results in one of the bearing cones being "screwed" more and more tightly into the bearing, eventually making the bearing too tight to turn.

The good news is that the above second case rarely results in "fatal" damage (though it may have the effect of adding a few thousand miles to bearing wear). So long as the situation is corrected and the bearing not "forced" to ride a considerable distance the damage is usually minor.

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  • Yep - it sounds like the second cause is probably the case; I likely did not properly tighten the locknut. I'm trying to understand how a loose locknut would result in a massively overtightened cone though. Would the axle itself have been rotating? Now I just need to figure out how to get the cones unscrewed. Thanks!
    – Matt Jones
    Feb 15, 2014 at 2:46
  • @MattJones - The wheel was rotating, the axle stationary. Depending on the way the forces worked out either friction or "precession" would have screwed the cone nut tighter and tighter.
    – Daniel R Hicks
    Feb 15, 2014 at 3:32
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If you over tighten the nut it will squash the bearing cage and damage the axel if your not careful ie new wheel

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