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I built my wheels up with 100kgf spoke tension (open pro on chorus 32 hole hubs and ACI butted spokes) but when I recently checked the tension, it only measured 60kgf.

Thinking the spokes must have stretched, I've just put the wheel in my truing jig to re-tension the spokes and now that I've removed the tyre, the tension measures up around the 100kgf mark again.

So: should I aim to have the spokes tensioned correctly with the tyre inflated or leave the tension as it is? (Tyres are Hutchinson Fusion 2 tubeless inflated to 90psi)
 

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Two wheels=freedom!
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IMHO, Once the wheels are built up, put your gauge away unless you are having problems keeping them in true.

I would assume that you made sure the spokes were evenly tensioned during the build, and remained so after truing the wheel.

Spokes don't "stretch" any appreciable amount. If you were carefull during the build to properly bend the spokes at the crosses and the heads, you should not have to worry about tension. If you did not bend the spokes during the build, then yes, you might see lower tension after the wheel settled in. But if you are still keeping in true, then you should be fine.

Funny thing, over the years, I've built over 100 wheels for both Road and Mtn, never once used a tension gauge, never had any problems.

If it aint broke (out of true) don't fix it!
 

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wow

hugphot said:
I built my wheels up with 100kgf spoke tension (open pro on chorus 32 hole hubs and ACI butted spokes) but when I recently checked the tension, it only measured 60kgf.

Thinking the spokes must have stretched, I've just put the wheel in my truing jig to re-tension the spokes and now that I've removed the tyre, the tension measures up around the 100kgf mark again.

So: should I aim to have the spokes tensioned correctly with the tyre inflated or leave the tension as it is? (Tyres are Hutchinson Fusion 2 tubeless inflated to 90psi)
So, you saying that simply inflating the tire caused the spoke tension to drop by 40%? I'd retest a few times and check for consistency.

If this is happening, then the only physical means would be that the tire pressure is causing the rim to be deformed inward, removing tension from the spokes, right? I suppose that is theoretically possible, but I'd want to recheck it a few times. I'd mark the spokes and test specific spokes with and without pressure.
 

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40% does sound excessive. But I always build to, as I found out after I bought an FSA tension-meter, around 130Kgf. And the inflated tires subtract maybe 10%.

Regards the 130Kgf, I also checked as many old (pre-cheap Park Tool TM-1 tension-meter) wheels people have been riding for years. They almost always were around or above the 130Kgf mark. None had failed. I think those tension-meters are causing unnecessary anxiety among the cycling community.

While I do use a beam torque-wrench to check my work on other components, the specs for rims I will disregard as my wheels have been rolling a long time with no problems, and trued to less then .25mm lateral-true and under .5mm vertical-true.
 
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