Why does a wheel go out of true?

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orderodonata
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Why does a wheel go out of true?

Postby orderodonata » Fri Jan 18, 2013 12:58 pm

Just curious, what is the mechanism (apart from damage) of a wheel going out of true?

Is it because the spoke nipples loosen and turn, or the spokes stretching, or what?

I suppose it's probably the constant bumps in the road leading to the spoke nipples loosening off, in which case wouldn't a bit of threadlock be a good idea?
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Yossie
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Re: Why does a wheel go out of true?

Postby Yossie » Fri Jan 18, 2013 13:09 pm

Because, much like Armnstrong, its a lyin' cheatin' b*stard.
This is only a joke by the way, I am in no way implying directly or otherwise that there is any kind of link or similarity between BR and North Korea :)

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ride_whenever
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Re: Why does a wheel go out of true?

Postby ride_whenever » Fri Jan 18, 2013 13:35 pm

The only reason that wheels go out of true aside from damage is that they aren't built properly.

A properly built and stress relieved wheel simply does not go out of true unless it is damaged. The tension should be high enough to prevent the spokes unwinding, and there should be no residual torque in the spoke from tightening that could slip under loading and effectively loosen the spoke.

thecycleclinic
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Re: Why does a wheel go out of true?

Postby thecycleclinic » Fri Jan 18, 2013 22:08 pm

Also when riding particulaly out of saddle the torque on the wheel can cause the NDS spokes to go slack. This means the spokes can loose tesnion. If there is low tesnion spoke somewhere that is the one that can unwind. Also a wheel that is not laterally stiff enough can flex too much. Lack of lateral stiffess can be caused by narrow flanage seperation, a light weight flexible rim, low spoke counts and thin spokes or a combination of the above. This is why a wheel builder will ask you a number of questions before commiting to a build.

Also spokes can loose tension going over lumps and bumps. The odd thing though a wheels radial stiffness is dependent on the spoke count. It is dependant on the radial stiff of the rim and that it.

So insufficent tension and un even tension are only one cause. The wrong rim, spoke count, spoke gauge and the wrong hub for the riders weight, riding style and road conditions all contribute. Bad wheel buildin is the other cause.
http://www.thecycleclinic.co.uk -wheel building and other stuff.


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