[fallzboater]

I understand how and why tire pressure causes circumferential rim compression and resultant reduction in spoke tension, but I was surprised to learn how much.

I just built a wheel with a 32h PowerTap SL+ hub and Velocity A23 rim, 2x with DT Comps and brass nipples. This is a fairly light rim (435g) and I weigh 180 lb, so I didn't want to go too high on the max spoke tension. However, due to the flange spacing, the tension ratio is pretty poor. I'm running a Hutchinson Intensive Tubeless tire, now, but may also run a 28mm slick or 33mm cross tire on it.

I greased the spoke holes in the rim and used WS Spoke Prep on the threads. I stress-relieve by squeezing parallel spokes, and remove any windup by pushing down on the rim with the wheel laying on its side. Using a Park Tensiometer, I started with about 125-130 kgf DS tension, and had some NDS spokes loosen on the first ride (55miles with 4,500' of climbing).

After re-tensioning/balancing, and measuring a few spokes, I currently get the following aproximate tensions:
At 20psi: 125kgf DS, 70kgf NDS
At 90psi: 100kgf DS, 60kgf NDS

If I continue to have NDS spokes loosen, I may increase the tension some more, or try some Loctite on the NDS nipples. Lacing the DS radial or 1x heads in, and OSB rim, or lighter NDS spokes might have helped, Any other observations or suggestions?

 

[rruff]

Seems like a solid build and 60kg should be fine on the NDS. If you have plenty of derailleur clearance, you can lace the DS heads-in and that should solve your problem, but I wonder again if the stress relieving wasn't aggressive enough, so the spokes are settling in as you ride.

 

[fallzboater]

Thanks for the reply. Yes there may well have been some settling, in addition to the drop in tension with tire pressure. How many rounds of spoke-squeezing do you use, or do you have another technique that you like? I'm stronger than average, but maybe I need to use some heavier gloves.

I'd considered using another DS pattern, but it was a used hub that had already been laced 2x, and I prefer to cover the old flange marks.

 

[Mike T.]

How many rounds of spoke-squeezing do you use, or do you have another technique that you like?

Do all the techniques that are on my wheelbuilding page. There's every technique I've ever read about there - and I do 'em all. If I can find more I'll add them. No spoke ever dares loosen off.

 

[rruff]

I don't squeeze the spokes, but rather lay the wheel down and press on the spokes at opposite sides of the rim, and on the NDS and front I press on the edges of the rim also. Each spoke gets hit twice, and I generally do this 4 times after the tension is up and even, and the wheel is true. When the tension on all the spokes stays the same and the wheel remains true, you know you are done. The hard part is knowing how much pressure to apply. You want the parts that need it to yield slightly (spokes, nipples, interfaces, hub flange, etc), but you don't want to go so hard that you tweak the rim.

I mostly use oval spokes so squeezing is difficult, plus I don't think you can get the same degree of tension increase that way. On the other hand, there is little of no chance of over doing it, but a greater chance of under doing it IMO.

 

[fallzboater]

I'll try that technique, thanks. I'm always afraid that I'll rip the nipples out of the rim, but it never seems to happen.

 

[Kerry Irons]

On and off

After re-tensioning/balancing, and measuring a few spokes, I currently get the following aproximate tensions:
At 20psi: 125kgf DS, 70kgf NDS
At 90psi: 100kgf DS, 60kgf NDS

Can you go back and forth on this? IOW, do you see the tension go back to the original numbers after you ride, then deflate your tires again?

 

[fallzboater]

Can you go back and forth on this? IOW, do you see the tension go back to the original numbers after you ride, then deflate your tires again?

Yeah, it's repeatable. I had the wheel in my living room and took the pressure up and down a couple of times. It may be worse, with these fairly light and wide rims, than what you'd see with most others. I've also noticed a significant change if you measure spoke tensions immediately after bringing a wheel inside in cold weather, vs. allowing it to come up to room temperature.