lock nut spacing / rear frame spacing mismatch

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lock nut spacing / rear frame spacing mismatch

Postby yugyug » Tue Jan 21, 2014 8:43 pm

I recently bought an old steel frame mountain bike and noticed that its rear wheel was dished or out of dish (?) but anyway leaning to one side. It must have be known about because the cantilever brakes had been adjusted for it so the wheel spun ok.

I took off the wheel to check it out and it seems the rear frame spacing is 13.5mm but the locknut spacing on the hub is 12.5mm or so and the outside nuts (no quick release) were just tightened, especially on the left side, to squeeze the frame in. This is what causes the dishing problem I think. The frame symmetry seems ok.

If I am reading the problem correctly (am I?) then what is the best solution - Sheldon Brown's page says the frame can be bent in, or that spacers which can be used on the axle, I guess outside the lock nut? Seems to me that an extra 5mm thick nut on either side would work - is that right or are there special spacers??

thanks in advance
Last edited by yugyug on Tue Jan 21, 2014 8:58 pm, edited 2 times in total.
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by BNA » Tue Jan 21, 2014 8:47 pm

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Re: lock nut spacing / rear frame spacing mismatch

Postby mitchy_ » Tue Jan 21, 2014 8:47 pm

135mm is a standard mtb frame width, sounds like you have a 126mm wide hub (6/7 speed?) stuffed in there. surprised that the frame hasn't had issues with the dropouts being cranked in tight.
ideally you want a 135mm hub put in there, as well as getting the frame checked...
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Re: lock nut spacing / rear frame spacing mismatch

Postby yugyug » Tue Jan 21, 2014 8:51 pm

Yeah its a 7 speed shimano cassette marked UG which I guess is uniglide.

Maybe the frame does have issues! I only just got it. But I checked the symmetry with the string method, seems fine. Is there anything else I should look for on the frame?

I don't really want to replace the hub - its an old but nice bike I just want to fix it up cheaply for so I can ride off road a bit. Wouldn't spacers work?
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Re: lock nut spacing / rear frame spacing mismatch

Postby il padrone » Tue Jan 21, 2014 8:58 pm

Must be old 7 spd or a road 7 spd used for a wheel rebuild as the old MTB 7spds from the early 90s had 135mm hubs.

Cheapest solution is to get the frame squeezed in, ideally by your favourite LBS workshop. It should only cost about $30. The better solution would be to get a proper 135mm hub and rebuild the wheel (costly). You may be able to track down a 135mm axle and get a few spacers and rebuild the axle in the correct longer length. This last option will be a lot cheaper but requires some mechanical skills. Probably your best option if you feel you can do it, or get someone you know to do it.
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Re: lock nut spacing / rear frame spacing mismatch

Postby yugyug » Tue Jan 21, 2014 9:03 pm

il padrone wrote:You may be able to track down a 135mm axle and get a few spacers and rebuild the axle in the correct longer length.


cheers - you know I think the threaded axle itself might be for a 135mm - its very long relative to a road bike - it protrudes at least 23mm past the lock nuts on either side....
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Re: lock nut spacing / rear frame spacing mismatch

Postby il padrone » Tue Jan 21, 2014 9:07 pm

Ah, no worries then. This is a bolt-up axle then? Just track down some suitable spacers for the 135, then get the wheel dish checked out.
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Re: lock nut spacing / rear frame spacing mismatch

Postby yugyug » Tue Jan 21, 2014 9:14 pm

thanks. So what are suitable spacers?
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Re: lock nut spacing / rear frame spacing mismatch

Postby il padrone » Tue Jan 21, 2014 9:25 pm

You need 9mm width of spacers (preferably just one) placed on the non-cassette side. Try a LBS for some, they should be easy to come by.
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Re: lock nut spacing / rear frame spacing mismatch

Postby yugyug » Tue Jan 21, 2014 9:41 pm

thanks very much, will do.
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