DarKris

So I'm going to have my wheelset with 9x100 & 10x135 QR changed to 12x100 and 12x142 TA and I went to determine the spoke length required for the new hubs compared to my old hubs. I found that the TA hubs would need spokes that are 2.2-2.5mm longer than my current spokes.

I also calculated the spoke length so I assume that the actual spokes are rounded but I am not 100% sure. However based on the difference that I found, is there a significant difference to require new spokes?

cpach

How far did the spokes engage in the hubs on the wheels before? If they were flush with the end of the nipple or beyond it might be OK, but 2-2.5mm is kind of a lot in this case. The spokes need to be long enough so that they go past the edge of the rim--otherwise, the nipple will be in tension between the rim and the threads of the spoke, instead of in compression between the end of spoke threads and the rim. Too short and the nipples will be prone to failure. If you're anywhere near the borderline at the very least use brass nipples as they survive being in tension better-aluminum nipples will almost certainly fail if the spokes are significantly too short.

dsaul

It seems like it would make more sense to just get a new wheelset with the thru axle hubs, unless you have some really expensive rims.

DarKris

I just checked and they are flush reaching the end of the threads on the nipples with a few spikes extending past. Is it possible to get longer spoke nipples to make up the difference or no?

Regarding the current spoke nipples, the build used dt Swiss stainless steel spokes & spoke nipples.


The wheelset that I’m converting is 27.5 (650b). The cheapest wheelset that I could find that was 12x100 were the Hunt Wheels which are $359 + tax. I got the replacement hubs for ~$100 and a wheel build for both would be ~$140-150 re-using my current wheels (spokes not factored in if I 100% need new ones).

Dan Burkhart 

To calculate the spoke length, you will need the critical dimensions from the new hub. If the hub flange diameter and center to flange dimensions are the same as your old hubs, then the spoke lengths will be the same.
Typically, a difference of 10mm in the center to flange measurement means a 1mm difference in spoke length, so there is some room to fudge there.

DarKris

I did calculate these:



QR Front



TA Front



QR Rear



TA Rear

cpach

Longer nipples don't make any difference, the issue is if the end of the spoke goes past the rim or not. Your case sounds marginal. Based on what you've described I would not agree to build your wheels with those spokes. Also spokes in even the best built wheels undergo fatigue—if you have some good miles on the wheels it may be a good value in longevity to replace the spokes anyways.

Anyhow for $140-150 your wheel builder should be able to advise you on whether the spokes can be reused confidently.