spoke lengths: round up or down
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spoke lengths: round up or down
My understanding is that spoke lengths are generally forgiving rounded to the nearest even or odd number, plus/minus almost 2 mm and they will still fit without any problems. My question is whether it is optimal rounding these numbers up or down. A shorter spoke may not start showing threads beyond the nipple but could be shy of engaging threads in the head. A longer spoke may not bottom out its threads but still engage ample threads in the head of the nipple, while there is usually ample space within the walls of a given rim to allow for some spoke protrusion. Therefore, would people generally agree rounding up 1.5 mm is better than down 0.5 mm? Attached are a couple wheels I am working on in case there are any opinions.
Last edited by joedab; 05-28-22 at 10:17 AM.
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I'll go .5mm short, but not 1mm short IF I'm taking the erd to the top of the nipple heads. This keeps the top of the spoke well into the nipple head. Shorter is a sure fire way to promote the nipples popping their heads (for me, usually before 5000 miles). I've found I can usually poke 1.5mm above the nipple head without running out of thread. (I may hit the end of the threads, but I've found the softer nipple will simply distort around the spoke for a thread or so and not be an issue.)
Edit: This is a good reason to measure your rims for the erd and not take a published (or someone else's) value. Besides, published values may well have been printed before that rim went into production or a change make on the line.
Edit: This is a good reason to measure your rims for the erd and not take a published (or someone else's) value. Besides, published values may well have been printed before that rim went into production or a change make on the line.
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For me, it depends on how much I expect the spoke to stretch. I'm comfortable rounding rear drive-side spokes down a bit, since they will stretch the most, especially if using thin butted spokes. The others I might round up, unless that puts me at 2mm too long or more.
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I found a spoke calculator that allows for spoke stretch:
https://www.wheelpro.co.uk/spokecalc/
If you look at the 'log' tab it looks like
The stretched spoke lengths agree with the Spocalc results.
I've also found a (UK) spoke supplier that cuts to any length in 1mm increments.
https://www.wheelpro.co.uk/spokecalc/
If you look at the 'log' tab it looks like
Spoke lengths required
- Left : 298.2157 (will stretch 0.1969 to make calculated length).
- Right : 295.8789 (will stretch 0.4400 to make calculated length).
The stretched spoke lengths agree with the Spocalc results.
I've also found a (UK) spoke supplier that cuts to any length in 1mm increments.
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Always go longer. There's no downside. The head will be far stronger. They seem to calculate short all the time anyway.
I have 2 specific flat screwdrivers, one with a notch and the other with a tooth sticking up for starting the nipple.
I have 2 specific flat screwdrivers, one with a notch and the other with a tooth sticking up for starting the nipple.
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I'd go with longer. Worse case, you end up using nip washers to address shortages regarding thread length.
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given the tentative consensus on longer spokes, in this particular case:
either 1. all @ 290 2. round n-ds up 1.4 mm for half at 292 3. worth spending on 191?
splitting the distance between both, leads to the fourth option of 288 and 290, even though shorter.
regardless, stretch would seem to be negligible until getting into spokes double-butted above 15 gauge.
could all be trivial if a given spoke has ±2 mm between either bottoming out or exposed threads ..
either 1. all @ 290 2. round n-ds up 1.4 mm for half at 292 3. worth spending on 191?
splitting the distance between both, leads to the fourth option of 288 and 290, even though shorter.
regardless, stretch would seem to be negligible until getting into spokes double-butted above 15 gauge.
could all be trivial if a given spoke has ±2 mm between either bottoming out or exposed threads ..
Last edited by joedab; 05-28-22 at 11:05 PM.
#9
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Longer always if available--you have a ton of room past ideal before anything bad happens. Even if you start having to force the last half turn or so to get ideal tension its not the end of the world. Here's a good explanation of why: https://wheelfanatyk.com/blogs/blog/...ed27ffcf&_ss=r .
With your specific situation I'd probably build with 290 and 292 if I had them (or were ordering), would feel OK building with 290s all around otherwise.
With your specific situation I'd probably build with 290 and 292 if I had them (or were ordering), would feel OK building with 290s all around otherwise.