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Old 09-20-12, 09:16 AM   #1
RaleighSport 
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How bent is too bent? (wheel question)

I did a bike emergency swap out this morning for a family member, they had fallen while on the bike and stepped on their rear wheel bending a section a good couple inches out of true.. these are decent alloy rims.. is the rim toast? The section is probably 1' of the diameter of the rim itself
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Old 09-20-12, 09:46 AM   #2
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It depends on the exact nature of the bend, but a decent mechanic who knows what he's doing can bring back almost any wheel that still turns within the fork or frame, and many warped worse than that. Often a wheel can be made very decent, as in close enough that you can still keep brakes adjusted, but not perfect.

There are those who insist on perfect wheels, but most urban riders realize that all the road hazards you encounter, you either learn to accept imperfect wheels, or you go broke pretty fast.

Bring the wheel to the local guy, and if he says he can save it for a decent price, do it.
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Old 09-20-12, 09:49 AM   #3
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Originally Posted by FBinNY View Post
It depends on the exact nature of the bend, but a decent mechanic who knows what he's doing can bring back almost any wheel that still turns within the fork or frame, and many warped worse than that. Often a wheel can be made very decent, as in close enough that you can still keep brakes adjusted, but not perfect.

There are those who insist on perfect wheels, but most urban riders realize that all the road hazards you encounter, you either learn to accept imperfect wheels, or you go broke pretty fast.

Bring the wheel to the local guy, and if he says he can save it for a decent price, do it.
I was more thinking as a project for myself when things get slow again, I've already swapped out the family members wheel for an almost identical looking one that they can keep. FYI, the wheel could not turn in the frame, it rubs the non driveside stays now and the brake.
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Old 09-20-12, 09:51 AM   #4
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There are those who insist on perfect wheels, but most urban riders realize that all the road hazards you encounter, you either learn to accept imperfect wheels, or you go broke pretty fast.
That's one reason why my commuter bike has drum brakes.
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Old 09-20-12, 10:08 AM   #5
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I was more thinking as a project for myself when things get slow again, I've already swapped out the family members wheel for an almost identical looking one that they can keep. FYI, the wheel could not turn in the frame, it rubs the non driveside stays now and the brake.
One thing FB did not note is that part of the process to save a wheel that has had force applied to it (such as being stepped on) that resulted in the bend is physically bending back the rim. It technically can be done by someone with less experience but it is not simple to bend back the right amount so that one ends up with fairly even spoke tension and therefore both a more true wheel and a stable one. With a bend that severe I generally recommend a good wheel person do the repair.

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Old 09-20-12, 10:51 AM   #6
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cny-bikeman raises a good point. You'll notice that I said it depends on the nature of the bend. There's a subtle distinction between a bent and a warped rim, the issue being how local bends are and and how much local force is needed to overcome them. Warped rims (looks like a potato chip) come back pretty nicely, but a local bend like from a pothole needs big differences in spoke tension to compensate for the rims desire to stay bent.

If you're willing to undertake this as a DIY learning experience, you can probably get it decent if you're patient and bring it home by degrees. Don't crank down on any few nipples trying to bring an area back to center, but instead work broad areas bringing the worst up to the 2nd worst, then continuing by always just bringing the worst areas in a bit, as you work around the rim. Be sure to work from both sides toward the middle. When you get reasonable close, you'll want to confirm that it's dished to the center of the hub (not the flanges of a rear wheel).

Good luck and don't get flustered.
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Old 09-20-12, 10:51 AM   #7
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One thing FB did not note is that part of the process to save a wheel that has had force applied to it (such as being stepped on) that resulted in the bend is physically bending back the rim. It technically can be done by someone with less experience but it is not simple to bend back the right amount so that one ends up with fairly even spoke tension and therefore both a more true wheel and a stable one. With a bend that severe I would recommend a good wheel person do the repair.
That's the fun part. Loosening the spokes, laying it on the ground, and carefully stepping on the rim to bend it back ..... Gotta have calibrated toes

Then it's up to you to define "good enough"
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Old 09-20-12, 01:40 PM   #8
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That's one reason why my commuter bike has drum brakes.
And mine as well. Currently, two of our bikes have drum brakes, and three have Shimano rollerbrakes. Rim brakes are disappearing from my household.
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Old 09-20-12, 02:00 PM   #9
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Fourty-two.


One of my Co workers in a shop used a Newtonian approach..
there was a post sticking out from the wall, which was solidly braced.

putting the wheel with the dent from hitting something, and flat spotting it ,
was hung over the post , then slammed down from the inside out
with a force similar to the one that deformed the rim in the 1st place..
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Old 09-20-12, 02:12 PM   #10
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...a local bend like from a pothole needs big differences in spoke tension to compensate for the rims desire to stay bent.
Sorry, but another clarification. You have to bend the rim back before you attempt any correction using the spokes. If the rim is bent to one side the spokes on that side will already be loose, the ones on the side away from the bend already tight, so one has to push it back somehow so that you can have both decent tension and useable trueness. If the spoke tension from one side to the other is wildly different the wheel will just fail again.

The technique varies depending on whether the bend is symmetrical or not and the preference of the person. Some do it with the wheel laced, some unlace completely, some push with their hands, others stand on the rim, and some just wack it on a bench. The asymmetrical bends typically are dealt with by putting the wheel in some sort of slot-type opening and twisting in the opposite direction of the bend. I've done all of the above.

Nobody can tell you if you have enough experience and the right touch to bring back such a wheel with a combination of bending and spoke tensioning. You can try it to maybe save some money, or pay someone else to try. Depending on the shop they may say it's not worth it, may charge you even if the results are not good, or may agree to try without a charge if they can't get it to "AGAP" standards. Either way be prepared for the possibility of needing a new wheel.
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Old 09-20-12, 02:21 PM   #11
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There are those who insist on perfect wheels, but most urban riders realize
that all the road hazards you encounter, you learn to accept imperfect wheels.
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Old 09-22-12, 12:04 AM   #12
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I flipped over my handle bars after hitting a pot hole. Front rim was tacoed. I took the wheel off of my bicycle and hammered it on the curb (hittig at the tire only) until the rim was true enough to ride home. When I got home I fine tuned the wheel true and checked rim for flat spots. I'm still using that front rim but I had to replace my front fork.
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