Originally Posted by
WizardOfBoz
Velocity Wheels kindly recommends between 110 kgf and 130 kgf. But this is for all of their rims, and they have a lot of different kinds. And they state "the mark of an excellent wheel builder is the ability to find the highest tension a rim will allow while maintaining its radial and lateral true." I don't agree. I mean, they have some experience, but this statement is at odds with people like Damon Rinard, Jobst Brandt, Musson, and Schraner. In fact, Rinard's stiffness test would seem to indicate that you get the same lateral stiffness at a range of tensions. And engineering reasoning would have you use a tension that is in that range, perhaps near the high end, but with some allowance for increased stress due to bumps, moshing the pedals, etc. Further, if you get close to the max, you stand a higher chance of potato-chipping the rim. It seems to me (PhD in engineering FWIW), that there's no need to get the rims to the point just adjacent to buckling.
The idea behind this is that the higher the tension, the more of a hit you can take without a spoke going slack. How much tension you can apply is a function of the rim strength (lateral and radial and tensile - for spoke pull-out)
Basically you need enough tension that the spokes don't go slack, and not so much that the rim starts to fail or potato chip. The stronger your rims are, the more of a range in acceptable tension you'll have. I don't remember if it was Brandt's book, but somewhere in the literature I've read it said to keep laying on the tension until the wheel starts to potato chip, and then back off a half turn or so all around, and that's basically the same idea.
The real value in your tensionometer is getting all the spokes with even tension, rather than one specific tension value.
And here's a photo of my rim with the important stats printed right on the decal... I think they sell a lot of these to engineers.
I'd be really surprised if your 40-year old rims could stand this much. I'm sure you can do the conversion, but 1200N = 122kgf so that's in the middle of the range Velocity is giving.
