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tidelag said:
How can somebody believe that the wheeltrueness decreases when one add a tire? Eric killed a myth with his video?
Simple, because no rim is without internal stresses. When an additional force acts on the rim things will change. It's difficult to see, but when you watch carefully the read outs on the video with and without tire aren't identical. Also, no tire is perfect. The casing thickness and shape uniformity varies and thereby effects how it acts on the rim. If you have a pair of accurate calipers you'll also find that clincher section of a rim will slightly spread open as you pump up the tire. (note, were talking very small variances here. Not something you would normally consider actually "going out of true".)

Recently I asked for help here about my crappy 24 spokes wheel. Got ~7% difference in tension, which seemed okay. But it did recently go out of trueness recently so my suspection is that this wasn't stress relieved good enought by me. dammit! ;)
That's why I searched more about stress relieving.
When I have got more time, I'll try to do it more carefully.
Or I'll build a new wheel, I does not know yet.
Aside from durability, being able to maintain tolerances after it has been ridden, is proof of a properly built wheel.

BTW, there's an easy bench test that will confirm whether your wheel will stay true during use. Put axle on ground (preferably a piece of carpet so you don't damage it), press on opposite sides of the rim. Go all the way round at every spoke of the same hub side and do both sides of the wheel.

When your wheel has been built well you'll only have to make minor corrections after this procedure. Repeat until wheel stays with-in the same tolerance.....a badly built wheel will never stay the same and you'll be repeating this procedure forever.

BTW2, make sure you also correct for optimal spoke line. Without it your build won't be good either.
 

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wheelbuilder
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divve said:
It's difficult to see, but when you watch carefully the read outs on the video with and without tire aren't identical.
They are two different wheels. You have a point and I'll have to redo the video and compare the same wheel with and without a tire for more imperical evidanve of what you are talking about. I'll also measure for any rim expansion (at the brake track). I use 120psi because that is a real world pressure. Higher pressures offer no benefit. I'll shoot them up to 140 just for S&G.

-Eric
 

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divve said:
If you have a pair of accurate calipers you'll also find that clincher section of a rim will slightly spread open as you pump up the tire. (note, were talking very small variances here. Not something you would normally consider actually "going out of true".)
Thanks for nuancing it more, that was a factor I forgot. (or did not grasp)

BTW, there's an easy bench test that will confirm whether your wheel will stay true during use. Put axle on ground (preferably a piece of carpet so you don't damage it), press on opposite sides of the rim. Go all the way round at every spoke of the same hub side and do both sides of the wheel.

When your wheel has been built well you'll only have to make minor corrections after this procedure. Repeat until wheel stays with-in the same tolerance.....a badly built wheel will never stay the same and you'll be repeating this procedure forever.
Well, one can damage the hubaxle, the ballbearings or the rim, so it was why I did not
mentioned the procedure.
That's why I want to do first what Jobst Brandts recommends; a least four spokes+two hands.
Read what he says himself: http://www.sheldonbrown.com/brandt/stress-relieving.html
"Pressing axially on the hub, while supporting the rim, requires a force larger than is manually possible..." so it seems pointless to do so.

BTW2, make sure you also correct for optimal spoke line. Without it your build won't be good either.
Good spoke line - that's means a straight spoke line from the hubflange to the rim?
One bends it carefully with hands, or a plastichammer?
(according to Sheldon Brown's page)

[thanks to Mark McM for pressure information,very useful]
 

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tidelag said:
Well, one can damage the hubaxle, the ballbearings or the rim, so it was why I did not
mentioned the procedure.
That's why I want to do first what Jobst Brandts recommends; a least four spokes+two hands.
Read what he says himself: http://www.sheldonbrown.com/brandt/stress-relieving.html
"Pressing axially on the hub, while supporting the rim, requires a force larger than is manually possible..." so it seems pointless to do so.
Wheel building is a procedure that requires careful attention to detail. The better you control that process, the better your wheels will be.
I specifically didn't mention the words "stress relieving". Instead, I used the term bench testing. The procedure that I outlined upsets the balance in your newly built wheel to the extent that it will expose the weakness of your build. It's an easy method that will allow you to find the tweaks that are necessary for the "perfect" build, without having to actually ride the wheel first. You won't destroy your wheel. Use just enough force for the "system" to be stresses. When done properly, in most regular builds you'll hear the non-drive side spokes relaxing. The other sides won't relax enough due to the higher tension.
 

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NeoRetroGrouch
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In all this I haven't read anything about equal spoke tension. Did I miss it? I hope that you place + or - 1% spoke tension (or the best you can measure) well above the last 0.05mm radial or lateral trueness. - TF
 

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That was covered way in the beginning when we mentioned as good as the parts will allow...or something to that extent.
 
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