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I am building a wheel and it is (pretty much) perfectly dished

Spoke tension calculator measurements say: enter image description here

However, my wheel required a lot of offset to get the dish correct. My park tool TM-1 verified that my tension is thus,

Non Drive Side Tension

TM-1 Reading: 16

Spoke Tension (KGF): 73

Drive Side Tension

TM-1 Reading: 20

Spoke Tension (KGF): 110

My rim manufacturer says:

o lo

Is 73 KGF too low to ride the wheel?If I keep proper dish I could probably only go up by 1 TM reading on both sides.

Here is a picture of the wheel if you care:

enter image description here

  • FWIW, The Park TM-1 isn't the easiest tool to get consistent results from. I use it more to ensure that the wheel tension is even rather than getting to a specific value. – Fred the Magic Wonder Dog Jun 15 at 16:48
  • @FredtheMagicWonderDog I was getting pretty consistent readings as long as the tool was touching only the 1.7mm surface. My spokes are double butted, so if you accidentally clamp the tool halfway on the 1.7mm and halfway on the 2.0mm the readings are inconsistent. – Kolob Canyon Jun 15 at 18:39
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The left to right side tension numbers you have are thoroughly normal. 70%-ish is where a lot of disc wheels land.

Once you're actually building the wheel, as opposed to planning it, you're only looking at the more tensioned side to see how close you are to your target tension. The other side falls where it falls. Since you're within the recommended range now, stopping would be perfectly reasonable. The extra 10kgf on the drive side would buy you more strength but also a little less fatigue resistance in exchange, plus you're in the range where windup can be a handful. (Sometimes while learning, builders can overshoot tension and make the wheel unstable, even to the point of ruining it, but this rim is likely far too stout for that.) It's not a totally marginal amount of strength gained, especially if the wheel is going to see the kind of riding where it will die by violence before it ever dreams of cracking from fatigue, but there are tradeoffs either way and you'll gain some experience in making the call either way.

Note also that this is the exact place where the whole third power of the smallest inscribed diameter thing comes into play in a major way for a newer wheelbuilder; getting that extra 10kgf out of 1.7s and still having a windup free finished wheel is well within what a skilled wheelbuilder can do, but it takes practice to get there. Presuming your tensiometer is telling you right, you won't be able to do it successfully without good overshoot and backlash technique. The reasonable limit for a 1.7 even for an expert is probably about 130, and in practice most applicable rims max out at 120 like yours. In comparison, if they were 1.8s it would be much easier, and 2.0s make it trivial. Yet on the flip side, the nagging irony is that thinner spokes mean more elasticity which means more innate resistance to rim fatigue, which brings the choice to go for more strength closer to being all upside. Most of the time, it would be the right thing to do in a professional setting I feel.

https://www.engineeringtoolbox.com/torsion-shafts-d_947.html

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  • What is windup? – Kolob Canyon Jun 14 at 6:16
  • @KolobCanyon Windup is when tightening a spoke nipple causes the spoke to twist with it and get held that way under the tension. Then when the wheel is ridden, compressive loads cause the tension to be released and the spoke can unwind, potentially causing the wheel to go out of true. Windup is prevented by wheelbuilders in a few different ways. That is a larger conversation but the basic skill is to overshoot your intended adjustment and then turn the wrench back to where you want. Conventional wheels can typically have windup eliminated this way, but there are fancier approaches too. – Nathan Knutson Jun 14 at 8:44
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    Just want to add that adding air to the tube/tyre changes the spoke tension. I don't know if you took the readings with or without it, but the picture has it, so I thought I should mention it. – abdnChap Jun 14 at 12:31
  • @abdnChap it's funny that you mentioned that. I noticed the tension dropped massively when installing the tire. I re-tensioned it with the tire on. I'm going to do one ride on it today and then check it after the ride. – Kolob Canyon Jun 14 at 17:13
  • FWIW, I've tried all the tricks to eliminate wind-up and I still get a few pings on the first ride of a new wheel build. The ping is a distinctive noise of a spoke releasing it's windup under lower tension. But I am not a pro only build one or two wheels a year. – Fred the Magic Wonder Dog Jun 15 at 19:21

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