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So, theoretically, can I strip an old rear 700c wheel of its rim and then use same (aluminum) rim to build a wheel with a different hub and different spokes? I'm aware that stressed aluminum is dangerous, but I wonder if one can get away with it.

Any advice appreciated.

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    There's nothing wrong with it, if the rim is in good condition. Generally one should not reuse the spokes, however, and economically it's often cheaper to just buy a new wheel. – Daniel R Hicks Nov 30 '17 at 23:13
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    As long as the rim brake track is not excessively worn you can reuse the rim. Even if it is worn you can use it but expect to re-replace it sooner rather than later. You need the number of spoke holes in wheel to match the replacement hub, and the spoke length to be close enough. If its a rear, do keep all the drive side and non-drive side spokes separate. I'd consider replacing all the spoke nipples anyway. I would not bother with new spokes unless they're corroded or kinked or have a habit of breaking. – Criggie Dec 1 '17 at 1:58
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    Reinforce @Daniel comment - Unless its a high end rim, a new wheel will probably be cheaper. – mattnz Dec 1 '17 at 2:13
  • @mattnz totally correct, but the question didn't reference price. I sometimes enjoy sinking hours into trying something new and learning. – Criggie Dec 1 '17 at 8:27
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Yes, absolutely, and it can make plenty of sense sometimes. Hubs failing early is one case. It has also become more frequent, although maybe not common, for people to want to swap carbon rims around, especially on disc brake wheels, because they have so much invested in the rim, and they can go a long time. I've rebuilt a handful of carbon rims in recent years for people playing with different hubs who wanted to keep their big dollar rims.

When you unlace the old rim, you want to do so in a fairly gentle, gradual way, especially at first when the spoke tension is still high. It's not good for rims of any material to be bent around unnecessarily, which is what happens if all the tension gets released at once on a spoke while the others are still tensioned. In other words, cutting the hub out like one does to re-lace a hub is not what you want to do here. What I do is go around doing detensioning layers of a half turn per spoke until I have quite low tension, then go to full turns. As soon as the spokes are sloppy loose, there's no tension and you can cut them or use a nipple driver in reverse from there.

Once you have your bare rim, it's a good idea if possible to check what kind of shape it's in without being acted upon by spoke tension. I always do this by taking a good quality new machined sidewall rim of the same size, laying it on the bench or ground, and laying the rim to be reused on top of that. You're essentially making a surface table out of the new rim, and it works well. Any lateral kinks or distortions will reveal themselves easily. Major radial dips or rises can be felt for this way too, but it's more subtle. If there are any radial distortions, the old rim probably isn't worth messing with. If you find lateral waviness inside of 2mm total gap or so it's probably fine; it will create some amount of tension imbalance, but only on the order of a couple quarter turn adjustments.

As far as fatigue, if you're gentle with taking the old wheel apart, there's not much difference between reusing the rim and continuing to ride the old wheel.

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People generally reuse hubs rather than rims because of the cost and lifespan differential.

That said, as long as the spoke count and dish/pattern* is the same, you should be ok.

  • Some rims are asymmetrical to account for brake or cassette dish. Even with a symmetrical wheel, you’d want to maintain the lacing pattern and dish to ensure the wheel isn’t encountering new stresses. So don’t flip a rear rim to the front and vice versa. Or at least be aware that this will further reduce the rim’s lifespan.

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