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Context: Bicycle wheels can become untrue if the rim is bent, e.g. from hitting a curb.

The usual question: Can a bent aluminium rim be bent back straight?

The two camps (figuratively):
1. Sure, go for it! See for instance: http://www.sheldonbrown.com/on-road-wheel-repairs.html
2. NEVER bend aliminium. See for instance some posts at: http://www.bikeforums.net/bicycle-mechanics/374083-pothole-damaged-rim-fix-replace.html

I have observed that many people hold an opinion in between. For instance Zinn in his book Zinn & the Art of Road Bike Maintenance claims that an aluminium rim can be bent as an emergency repair on the road (The Sheldon Brown link is also framed as conerning roadside repairs).

My question: Does bending an aluminium rim actually make it much more prone to failure?

I am well aware that the question can be interpreted in many ways and that it can produce low quality answers with anecdotal evidence. To prevent this, I will try to specify what kind of answers I do and do not seek:

  • Please do not mention one single instance when you bent a rim straight, then your rode it a few times and it still remained intact.
  • Please do not mention if your rim broke one, after bending it straight, as a result of an accident that could otherwise easily have bent it.
  • Answers that refer to multiple, well monitored cases observed over a long time are premiered. For instance, if you have bent several rims straight for several friends over 20 years of time and you know that each of them have ridden the wheels for a long time and that they would report if something went bad.
  • Please add details, such as how bent the rims were before you straightened them (approximate deflection from the straight wheel plane) and for how long and "how hard" the wheels have been ridden, if possible.
  • As an exception to the above points, I would be interested in single cases that a rim has collapsed after being bent straight, after being used under normal, not exceptionally straining conditions. This is because I have never ONCE heard of this happening. And I have seen and read about quite a few bikes in my time.

Although the question still can lead to multi-faceted I think that it is highly relevant. I think of this often, but I have been unable to find solid evidence for one camp or the other. Either people claim that bending rims has worked for them on few occasions, or they claim that "aluminium must not be bent", as if that were a universal truth without room for exceptions.

closed as off-topic by andy256, Móż, Gary.Ray Sep 8 '15 at 12:46

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If this question can be reworded to fit the rules in the help center, please edit the question.

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    Please do not give orders. This a free site for advice. Fact aluminum fatigues when bent and fatigues again went bent back. Aluminum even fatigues if it is stressed less than the yield point. -1 – paparazzo Sep 5 '15 at 20:15
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    I would edit your question to make it answerable, but the entire point seems to be your rant about what you don't want to hear. You seem to be asking for the job diary of a busy wheelbuilder over several years, with analysis. That sort of work costs money. – Móż Sep 6 '15 at 5:57
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    I'm voting to close this question as off-topic because because it's a rant. – andy256 Sep 6 '15 at 7:14
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This comes down to the difference between plastic and elastic flexing.

This is from the Sheldon Brown article you linked to.

Often, surprisingly, a lightweight rim is only flexed, not bent, and the wheel can be sprung back nearly into its original shape.

This refers to aluminum that has not been stretched beyond its elastic range. As long as you stay within the elastic range, you're okay.

It is damaging to bend aluminum into its plastic range. That's where you start to compromise its strength.

  • Incorrect on "start" to compromise. Aluminum will fatigue even when flexed within the elastic range. – paparazzo Sep 6 '15 at 10:25
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I've bent numerous WTB rims back after "pinging" them and creating a flat spot in the bead.. I've also done the dresser drawer trick to straighten a slightly warped rim. Yes the strength of the rim is always diminished. I've never had catastrophic failure but the WTB rims would just refused to be trued after a couple goes.

Mavic rims would stand up to more punishment but never responded well to brute force.

Long story short, If you value your safety and a true wheel and if you can't true it with spoke tension, get a new rim.

Maybe you should learn how to build wheels? it's not hard...

edit: oh yeah .. I forgot. 2005 whistler, mavic 213, bead lip bent back up and de-warped with a foot against a car tire. Catastrophic failure in a transition after a medium table-top on a-line. stiches required. Don't be cheap with your wheels.. they keep the rubber between you and the road.

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    Please see the help center. You are expected to be nice. Issues with the question should be addressed at the question, for example by reporting it for moderator intervention. – andy256 Sep 8 '15 at 12:41

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