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Spoke length rounding up/down?

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kwarwick

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Discussion starter · #1 ·
Appreciate advice on spoke selection for an upcoming wheel build that requires:

Front: Non drive side: 268.5mm drive side: 270.5mm
Rear: Non drive side: 271mm drive side: 269mm.

I'm planning on using DT Swiss Competition which generally seem to be available in even 2mm increments, so would it be better to use half 268mm and the other half 270mm spokes in this case?

Or could I get away with 270mm for all of them?
 
#2 ·
I'd round down if they are butted spokes because they can stretch. Just a little bit, but enough. I prefer to have enough length to get the spoke flush with the inside of the spoke head, but I've also ran out of threads on a spoke before. If you run out of threads, you can't tighten it any more, and you're just stuck.
 
Discussion starter · #3 ·
Thanks. Sounds like you're saying 268/270mm would be the safest bet? ERD of the RIM seems to be the wildcard as it is sometimes a few mm off from what is quoted and I don't have the patience to wait for the rims to arrive before ordering spokes.

Worst case the spokes end too short or too long and I get to replace half of them with the next increment up or down. Not like I haven't had that happen before regardless of how careful I try to calculate everything. ;-)
 
#5 ·
I think I might go with 270's all around.

It depends on the program used and more importantly the accuracy of the measurements that are imputed but I always rounded up without issues. Usually spokes can be at least 2 or 3mm beyond ideal without issue whereas slightly short isn't so good.
 
#6 ·
#8 ·
boomslang64 said:
I round down. A spoke too long ends your wheel build. A slightly short spoke is fine.
Click to expand...
I disagree. 2mm long is no problem, 2mm too short? Not ideal, especially when using alloy nipples. Way too long can end a build (happened to me many times) but you have to be pretty far off on the calculation for that to happen IME.

Yes, measure erd if at all possible, and measure on a few different points on the rim.
 
Discussion starter · #9 ·
Thanks for all the input guys! After reading all this (including the tale of woe) now I'm also thinking I should round up. I used 3 different spoke calculators and they all gave within .5mm of each other. Only one had the ability to compensate for the staggered spoke holes of the rims I've ordered (Light bicycle carbon 27.5+ 50mm). I also asked Light Bicycle to tell me what length spokes they use for their builds since they offer complete wheels with the same rims, spokes and hubs I've chosen and they provided the values in my OP. But again, its all about the ERD and considering these are essentially handmade rims I imagine variances are more than possible.
 
Discussion starter · #10 ·
Well just a quick update, and a warning about rounding down *too* much.

I recalculated spoke lengths using DT Swiss's spoke calculator and got slightly different values for spokes with the calculator recommending 268 and 269mm (using DT Swiss 12mm 14G nipples). Since you don't seem to be able to easily get 269 unless someone cuts them for you, I tried going with 268 for both sides figuring rounding down 1mm wouldn't be a big deal.

Well last night I found out otherwise... on the 269 side of the hub the 268s were just a little too short with ~1 spoke threads visible above the nipples. :madman: I know some wheel builders think a spoke thread showing is acceptable but not in my book so I was cursing thinking I'd need to source some 269 or 270mm spokes until I remembered I also had a stash of 14mm nipples. Sure enough the extra 2mm overall length and extra 1mm of thread in the outboard part of a 14mm nipple was just the ticket to correct this problem.

I guess I'm paying a slight weight penalty with the 14mm nipples, but I actually prefer them due to the slightly longer flats which gives a little more surface area for the spoke wrench to engage... if you've ever accidentally let the spoke wrench ride up a bit too far while doing the final tension and distorted the nipple you'll appreciate the benefit. :thumbsup:
 
#11 ·
Spoke length calculations are meaningless without accurate data. Garbage in = garbage out. The ERD measurement is critical. Don't trust published values. It's always best to get the rims and measure the ERD yourself. Then buy your spokes with confidence.
If you're really pressed for time buy extra spokes in various lengths so you have everything ready to assemble as soon as the rims arrive. Still make your own rim measurements and recalculate spoke lengths. Then just return the unused spokes to your vendor.
As for rounding spoke lengths, I was taught to round up if the calculation yields xxx.8 or more, and round down if its xxx.7 or less. YMMV.

Cheers,
-S
 
#13 ·
kwarwick said:
Well just a quick update, and a warning about rounding down *too* much.

I recalculated spoke lengths using DT Swiss's spoke calculator and got slightly different values for spokes with the calculator recommending 268 and 269mm (using DT Swiss 12mm 14G nipples). Since you don't seem to be able to easily get 269 unless someone cuts them for you, I tried going with 268 for both sides figuring rounding down 1mm wouldn't be a big deal.

Well last night I found out otherwise... on the 269 side of the hub the 268s were just a little too short with ~1 spoke threads visible above the nipples. :madman: I know some wheel builders think a spoke thread showing is acceptable but not in my book so I was cursing thinking I'd need to source some 269 or 270mm spokes until I remembered I also had a stash of 14mm nipples. Sure enough the extra 2mm overall length and extra 1mm of thread in the outboard part of a 14mm nipple was just the ticket to correct this problem.

I guess I'm paying a slight weight penalty with the 14mm nipples, but I actually prefer them due to the slightly longer flats which gives a little more surface area for the spoke wrench to engage... if you've ever accidentally let the spoke wrench ride up a bit too far while doing the final tension and distorted the nipple you'll appreciate the benefit. :thumbsup:
Click to expand...
Stop banging your head! Anything above the nipple is doing nothing.
 
#18 ·
I've rounded down on my first build by 0.3mm, so I should be safe. Was fortunate that all spokes ended up even/standard lengths (268/270/272). Spokes/nips arrive later on today, so we'll see soon enough. FWIW, I did measure the ERD on both rims before ordering spokes. :thumbsup:

What's the general consensus WRT greasing the nipple seat of the spoke hole to minimize spoke wind up?
 
#19 ·
carbine_275 said:
I've rounded down on my first build by 0.3mm, so I should be safe. Was fortunate that all spokes ended up even/standard lengths (268/270/272). Spokes/nips arrive later on today, so we'll see soon enough. FWIW, I did measure the ERD on both rims before ordering spokes. :thumbsup:

What's the general consensus WRT greasing the nipple seat of the spoke hole to minimize spoke wind up?
Click to expand...
I use oil. I put some oil in a jar and put my spokes in that jar thread down. And then make sure it's no dripping before I lace the spoke. It helps for a smooth application versus a dry squeaking when tightening. What do I know. I just follow wheel building book instructions.

Sent from my iPhone using Tapatalk
 
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