Spoke lengths - round up, or round down

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Smurfy

Naturist Smurf
I think you make a good point and particularly the sentence I highlighted. It would help any builder to understand exactly what the calculator is doing or not doing.

As for the various combinations of spokes and nipples, all the major spoke brands use a 9mm long thread. This includes SAPIM, DT, Wheelsmith and Pillar. Have you come across any with different thread length. In addition, nipples with exactly the same thread characteristics (for a given length nipple) include SAPIM, DT, Pillar and Lilly. Which ones have you come across that bottom out with different results? Perhaps I should ask about the particular combinations.?
I found that with Sapim 12mm and 14mm nipples, a Sapim double butted spoke will go all the way to the top of the nipple slot, but will only go as far as the bottom of the nipple slot with a 16mm Sapim nipple. The no-name double butted stainless spokes I recently removed from a wheel would allow 2mm of spoke above the nipple head.
 

Spoked Wheels

Legendary Member
Location
Bournemouth
Incidentally, the late Sheldon Brown used to round upwards. Post 12 http://www.bikeforums.net/commuting/371033-lacing-wheelbuilding-advice-needed.html
 

S.Giles

Guest
My way of looking at it (which may be overly simplistic) is this. The further you round down, the more the spokes (tend to) become difficult to thread, which is a gradual process. Rounding up, however takes you closer to the situation where the spoke's thread runs out. This isn't a gradual process, it's a brick wall (which you won't encounter until later in the wheel-building process). Personally therefore, I'd rather err on the rounding-down side of things.

On my latest wheel-build (last week), I calculated the ideal spoke length at 264.9, and ordered 264's, (rounding-down by 0.9mm). I subsequently ended up using a rim with a 1mm larger ERD than originally planned. I had therefore effectively rounded-down the spoke length by a further 0.5mm (so 1.4mm total). Did this cause any lacing problems? Not at all! The wheel still went together like a dream, suggesting there is some safety margin there.
 
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