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I have a rear wheel with a 29" WTP STp i25 rim. The rim is irreparably damaged, but the wheel is otherwise in good condition. The spokes are not affected, the hub is great, and the wheel was pretty new when it was damaged. It's been hanging in my garage as I mull over what to do with it. I think I'd like to rebuild it. If I could find an identical rim, I would (in very broad strokes) just need to undo the spokes (probably tying them together in such a way as to make the rest of the job a little quicker), re-lace onto the new rim, dish/tension, retension, voila!

The problem is that I can't find another one of those rims. I can find a couple of i29 rims, I think, but not the i25. So, my question: For my brilliant scheme to work, don't I just need another rim with the identical ERD? Or is there more to it? My goal is to repurpose as much as possible of the current wheel into the new build.

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  • Note that you need a rim with the same spoke count. Aug 13, 2020 at 0:38
  • Yes, you're right, of course. I should have stated that, but the need to explicitly state it didn't occur to me when I wrote.
    – Andrew
    Aug 13, 2020 at 14:14
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    I'd check if a replacement wheel doesn't come cheaper, unless for some conservation of historic material you wish to re-use the existing parts.
    – Carel
    Aug 13, 2020 at 15:30
  • @Carel - Yep, if you need to hire someone to swap the rims then a whole new wheel is almost always cheaper. Aug 13, 2020 at 17:15
  • The problem of pre-built wheels is that they are typically of poor quality. They may have non-Shimano hubs that fail in no time, straight gauge spokes as opposed to 2.34mm-1.8mm-2.0mm DT Swiss alpine III spokes and rims that lack double eyelets that prevent cracking around the spoke holes when the spokes are tensioned really high. The nipples also may not be optimal (i.e. they lack the DT Swiss "pro-head" feature that supports the load even at an angle). Also such pre-built wheels are often machine built, having undertensioned spokes that lack the stress relieving step.
    – juhist
    Aug 14, 2020 at 15:47

2 Answers 2

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Yes, you basically just need another rim of the same ERD. You actually have some wiggle room as long as you're tracking what the thread engagement was like on the first time and know which way to wiggle it. (Don't use aluminum nipples if you're going to have less than optimal engagement.) Also you can switch nipple lengths to have yet more options.

If it was an offset/asymmetrical rim, in theory that could throw it off and leave you with some spokes too long or too short, but it usually wouldn't make enough difference.

Looking way back in time, the "handedness" (offset orientation of the spoke holes adjacent to the valve) of rims didn't used to be universal like it is now, so you'd have to look at that on a vintage wheel you were doing this to.

Use new nipples. Rounding one off because of trying to save $2 wouldn't be good.

You can check how satisfactory the thread engagement is of the existing spokes, measure them, measure the hub, and then use all that information to calculate the ERD of your rim (or its ideal replacement) in reverse. SpoCalc makes it pretty easy to do that.

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Correct - your replacement rim MUST HAVE

  • The same number of spoke holes
  • The same Effective Rim Diameter (ie the surface where the spoke head rests on)
  • A suitable rim brake track if your bike has rim brakes

There is no need to have the same brand or style or width of rim, as long as the critical points are met. OPTIONAL thoughts:

  • Similar visual design, so the bike looks "balanced" or you could go completely different.
  • Internal rim width at the back could be wider than the front, allowing a wider rear tyre (assuming that the frame clearances are sufficient for that tyre) You would not gain anything from having a narrower rear rim.

Depending on what happened, you may choose to reuse the tube and tyre if they're okay. However I'd suggest a new rimtape straight away.

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