Wheelbuilding advice wanted from other builders.

daddylonglegs

Okay, I learned to build wheels twenty years ago when I worked as a mechanic at my local bike shop. During that time I probably built hundreds of wheels. Since I left I've kept my hand in over the years by occasionally repairing and building my own wheels.

The method I've always used to relieve spoke tension during a build is to use my hands to squeeze pairs of opposing spokes. I have also always laid the wheel on the floor or a solid surface and pushed down on the rim allowing it to flex slightly and giving any twists in the spokes a chance to unwind. I have never had a problem with this method.

Yesterday I was building a rear wheel using a Mavic 32 hole Open Sport with a standard 3x pattern. I was getting close to finishing when, while I was using the method described above to untwist the spokes the rim broke, coming apart at the join. One of the pins holding the rim together was pulled partially out and bent. Needless to say this brand new rim is a write-off.

Should this have happened? Have I just been lucky that it has never happened before? Is this method best avoided on cheaper, un-welded rims? Any comments from experienced wheelbuilders, Mavic reps(!?), wheel and rim experts and anyone else who think they can help would be greatly appreciated.

whyamihere

The method is fine. It sounds like you had a dodgy rim. Good job it broke when it did really, as if it hadn't I feel pretty sure it would have gone while riding.

ride_whenever

The method for untwisting you describe works for me although some people say it puts undue stress on the bearings and flanges, which is probably true.

Did you use a tension meter? Even so the rim shouldn't have broken, and mavic are pretty good about warranty, so I doubt you'll have an issue.

daddylonglegs

Thanks for the comments, I wasn't using a tension meter, but I never do. The spokes weren't particularly tight though and I was finishing the job so tension was even. The rim was mail order from Chain Reaction. Anyone know how they are likely to be over this? Uh-oh, I can feel the headache developing already...

dennisn

whyamihere wrote:

The method is fine. It sounds like you had a dodgy rim. Good job it broke when it did really, as if it hadn't I feel pretty sure it would have gone while riding.

+1

Dennis Noward

nmcgann

That happened to me too with a pinned rim (DRC ST17). I think I just pressed too hard on that occasion.

I still use that method to get out any residual wind-up in the spokes and haven't had any other problems.

Neil

balthazar

I suspect that you have two procedures - unwinding residual spoke twist, and stress-relieving spokes - muddled.

The second of your two methods (pushing against the wheel on the floor) is an old fashioned procedure for relieving spoke twist. Other methods included: bending the wheel in a half opened drawer; or walking over the spokes in your socks. I prefer Jobst Brandt's method, which is to account for spoke twist during the build, by overtightening then backing off each spoke. The result is a wheel which has no residual spoke twist to relieve.

Squeezing opposing spokes together hard serves a different function - stress-relieving. This procedure addresses a subtle problem in the material characteristics of the spokes, and results in a more durable wheel. Rather than attempt to explain it myself I'll refer you to the original:

http://www.sheldonbrown.com/brandt/stre ... eving.html

My feeling is that the rim failed because you pushed against it too hard. A wheel in use never sees the stress you gave it, and would never fail in this way. That is why I wince when I see people bending wheels like this. Welding the join, though serving no function in use, prevents rims breaking under the ministrations of an over keen builder, and I wonder if that is why they became common.