Changing Spokes? - Rim Damage?

[Chexjc]

I have a couple of questions. As anyone who's noted my Coker or Coker Parts thread in the Trading Post section knows, I'm helping a friend build up a 36" wheel. We already have mostly everything we need. For the rim, I've decided to upgrade my steel rim to the Nimbus Stealth Pro and sell him mine.

Ideally, I'd like to upgrade to the 14g Stainless Steel Spokes - but they are out of stock until the 30th. Because we'd like to build up his wheel ASAP and couldn't afford to do that regardless, would it be reasonable to reuse the same 12g spokes with the new rim and upgrade later in the summer to the stainless steel? Of course I've considered the additional cost of having the wheel rebuilt, but I guess what I'm asking is - will reusing spokes compromise the strength of the wheel? AND - will eventually switching from the 12g spokes to the 14g SS spokes compromise the rim at all?

Thanks,

Jason

[UniDudeDX]

there wil lbe no problem., but the spokes will be a little stretched...

[ntappin]

If you are using the same hub in both the your uni and his, then why not just you take his hub and he takes your complete wheel? That way it saves the wheelbuild, and guarantees strength. If you aren't going to have the same hub, then the spokes won't fit anyways.

[Chexjc]

Originally Posted by ntappin

If you are using the same hub in both the your uni and his, then why not just you take his hub and he takes your complete wheel? That way it saves the wheelbuild, and guarantees strength. If you aren't going to have the same hub, then the spokes won't fit anyways.

Because then I have no spokes to use, unless I use the set of used spokes that are already in shipment to him. I'd rather use my spokes, because I know what they've been through and what sort of condition they are in.

At the moment, we aren't sure what hub he is going to buy. I'm a little confused because UDC says the super-wide chromo hub is drilled for 14g spokes - but can be drilled for 12g. Does that mean they can drill it? If not, he's stuck with the narrower, wide chromo hub...which isn't a terrible thing anyway.

[Chexjc]

Bump.

[adelman]

Originally Posted by Chexjc

will reusing spokes compromise the strength of the wheel? AND - will eventually switching from the 12g spokes to the 14g SS spokes compromise the rim at all?

The short answer is spokes can be reused if they aren't damaged without compromising anything. I've got a mountain-bike wheel I've replaced the rim on twice that is still on the same set of spokes.

The long answer is a little more complex. When you take apart the old wheel, it is important to evenly release the tension on the spokes (say, one turn at a time) so that you don't deform the rim in the process. When you build up the new wheel, the wheel will be just as strong as if you used new spokes, provided you tension the spokes properly. However, the individual spokes, if not installed properly, may fail prematurely from fatigue.

A spoke in a wheel doesn't follow a straight line; it has a set of bends near the hub, a bend where it crosses the spokes that face the other direction, and a small bend where it goes into the nipple. A good wheel builder, using a few different techniques, pre-bends (or strain-relieves) the spokes, so that they are in the same shape absent the tension as they are with the tension. If you don't do this, as the wheel rotates in use, the spokes are like a paperclip being bend back-and-forth, and eventually work-harden and fail. In a properly built wheel the spokes don't fatigue in this manner -- actually, if I get normal service life out of a rim without any spoke breakage due to fatigue, I *prefer* to reuse the spokes when replacing the rim. Since they didn't fail, I take that as proof that they didn't fatigue and were property strain-relieved. Why would I want to start over and take my chance on a new set?

Spokes can always be reused if the wheel is build rebuilt with the same type hub and rim, and provided you keep the spokes in the same position (left inner, left outer, right inner, right outer). Changing the rim type usually isn't a big issue, but changing the hub flange shape could be. If you must reuse spokes in this situation, you may want to evaluate how different the shape might be and whether it would be possible to straighten them prior to lacing the wheel. Properly strain-relieving will be important.

If you totally ignore the bends in the spokes, reinstall them randomly, and don't strain-relieve, worst case is that the spokes suffer from premature fatigue and break one-by-one. Breaking of a single spoke shouldn't damage the rim. Properly tensioned, even if not property strain-relieved, the reused spokes will resist a "potato-chip" type failure of the entire wheel as well as properly tensioned new spokes.

You could re-drill the unicycle.com hub for the wider spokes, but you'll need to property bevel the edges of the new holes. 12g spokes are 2.5mm diameter; I'd guess you'd want a 2.7mm hole, or about a #36 drill bit. Beveling the edges is left as an exercise to the reader. If you later wanted to rebuild the wheel with 14g spokes, you'd need to replace the hub as well.

[Chexjc]

Originally Posted by adelman

...

Wow! You weren't kidding when you said "long answer." Thanks a lot! I'll have to have a talk with the LBS guy and see how comfortable he'll feel about doing this operation haha.