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Old 11-06-08, 10:40 AM   #1
h2o_polo_boi
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bent wheel in crash but rim is perfect?

I totaled my rear and front wheel in a bad crash. They were both bent beyond the point of repair, rubbing against the brake pads. Yesterday, I decided to build another wheel using the salvaged spokes, nipples, and hub. I took apart the rear rim. Turns out, the rim is perfectly fine when I set it on the ground. Looks true radially and vertically. Does that mean the rim is functional and can still be rebuilt or would the integrity of the rim be compromised? It's really strange for the wheel to be bent like crazy but the rim is fine. I wonder if it's because they're Mavic Open Pros.
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Old 11-06-08, 11:16 AM   #2
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If the rim is really round and there are no signs of cracking or crimping I'd think you should be able to use it.

Al
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Old 11-06-08, 11:22 AM   #3
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i guess the question i'm really after is why isn't my rim bent despite the crash. Seem's kind of puzzling to me. Do the spokes just take up the tension or did some spokes loosen up? Some (2-3 spokes) were slightly bent near the nipple but i was able to bend them back.
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Old 11-06-08, 11:25 AM   #4
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i guess the question i'm really after is why isn't my rim bent despite the crash. Seem's kind of puzzling to me. Do the spokes just take up the tension or did some spokes loosen up? Some (2-3 spokes) were slightly bent near the nipple but i was able to bend them back.
You should throw away the spokes that were bent. Bending and straightening introduced metal fatigue that will probably lead to failure.

Bob
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Old 11-06-08, 11:29 AM   #5
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You should throw away the spokes that were bent. Bending and straightening introduced metal fatigue that will probably lead to failure.

Bob
Even if it's steel? The bend was hardly noticeable and is nothing compared to the natural bend when spokes cross on the inside of trailing spokes.
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Old 11-06-08, 11:32 AM   #6
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Even if it's steel? The bend was hardly noticeable and is nothing compared to the natural bend when spokes cross on the inside of trailing spokes.
Oh, that kind of "bend". That's ok. From the description of the crash, I thought it might be some severe bends in the spokes.

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Old 11-06-08, 11:49 AM   #7
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Are you sure the wheels were true beforehand? They might have wandered a bit out without you noticing. I just happened to notice that my rear was out of true the other day, just because I happened to spend a lot of time near, but not on it.
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Old 11-06-08, 12:54 PM   #8
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Did you try truing your wheels after the crash? From the sounds of it, some of the spokes where bent from impact. This could cause them to pull with more tension than others causing the wheel to go out of true.

Most of the time, it's the rim that has a permanent bend that forces you to use very uneven tension to true. In this case, it's an unfixable taco and the rim needs to be replaced. After unlacing the rim, if you place it on a glass coffee table, you can see the taco shape.

In your case, if the rim's perfectly straight, I don't see why you can't reuse it. It sounds like some of the spokes got tweaked, and maybe some of the nipples were stripped, leading to uneven tension.
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Old 11-06-08, 03:19 PM   #9
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My thought on this is that if the rim looks perfect (no substantial scratches, dents, and the rim is 100% true and did not have to be bent back into original shape) then what might have happened is that only the spokes and or the hub was damaged. Metals have a specific amount of springiness. Up to a certain point a metal will flex under load and then return to its original shape once the load is removed without a change in the materials properties. Once you exceed this maximum point of springiness the material deforms and even if you are able to bend it back to its original shape it will have lost strength.

Is the rim true in all dimensions? It might lay flat on a table but is not necessarily true. From the side view is it a perfect circle? If the impact came not from the side but from a taller angle then it would lay flat but might be other than circle (egg shaped or a circle with a flatter spot on the outer diameter of the rim). Also what might have happened to your rim is the same thing that happens when you over tighten spokes which is the spoke nipples begin to stretch the material around the hole where the spoke nipple nests deforming and weakening metal around nipple hole which increase the chance that the whole nipple could ultimately just tear trough the inside of the rim. This could have occurred in your case from an impact to the spokes. In might have stretched the spoke nipple holes out which would cause the wheel to not spin true because the relative tension of the various spokes changed because of a permanent change in the shape of the wheel.

As for the spokes I would throw any away that show signs of impact or having been bent beyond the point of springiness even if they are steel. What you keep depends how careful you want to be. If you have several compromised spokes then a hard bump could lead a massive failure of several spokes causing your wheel to taco causing you do go down dangerously. But even one spoke breaking can be dangerous. I have seen a loose spoke wrap around the hub which caused the wheel to lock up which can be just as bad.
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