At 9:35 AM -0500 9/28/08, Earle Young wrote:
> By reducing the maximum
>variation in spoke tension to less than 10 percent, the increase in the
>strength of the wheel is about 20 percent (90 percent of maximum tension
>vs. 80 percent of maximum tension). If anybody has an issue with this
>logic, I would be glad to hear it. But if you want to dispute it, please
>do so with some numbers.
Since you threw down the gauntlet, I'll point out that you need to show that 1% reduction in spoke tension equals a 1% reduction in wheel strength before you apply the above logic. I suspect it's more of a threshold value. If your spoke tension goes below a certain point, the spokes work excessively, and will break prematurely. Of course, your reasoning that even spoke tension means that the least tensioned spoke is tensioned more, is correct.
I don't doubt that even tension is desirable. The strongest wheels probably are the ones you build up by tensioning (stepwise, as you describe) each spoke, and when you are done, the wheel is true and round, with no corrections needed. Unfortunately, this happens generally only with heavy rims and large spoke counts. The old Mavic GP4 built up like that sometimes, and I recently built a 40-hole rear wheel with a super-beefy Mavic Module 4 that needed only the most minor of corrections. I don't even use a tensiometer, but just pluck the spokes to even the tension by tone.
When you use lightweight rims, you cannot get even spoke tension and a true, round wheel. Your goal has to be to get the spoke tension as even as possible and still obtain a round, true wheel. Building a wheel with an old Scheeren wood-filled 270 gram rim is more an art than a science. Even so, wheels built by Spence Wolf with those rims have stayed true for decades, if they are not abused.
Also, some rims build up better than others. Mavic MA-2s were terrible, the current Velocity Synergies are very nice. That said, I have had zero problems with MA-2s once they were built, so the slightly uneven spoke tension apparently isn't a huge deal.
Jan Heine
Editor
Bicycle Quarterly
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