Bicycle Mechanics - Spoke Length variance allowed?

Hi,

Having built a few 3 cross wheels I wanted to try something different just for the fun of it.

I've got a pretty sweet price on some 290mm spokes, the front wheel is 32h, want to lace it 2 leading 2 trailing, and the rear is 36h, want to lead it 3 leadng 3 trailing.

Now, i've calculated the front to need 290.6mm spokes, so they'll be fine, but the back requires 292.6mm.

This on either side add's up to 5mm of a difference.

Will I be able to use 290mm spokes on the 36h wheel that requires 292.6mm? I'm using standard. 12mm nipples that protrude roughly 6.5mm out of the rim.

The spokes are threaded for around 10mm at the end of the spoke.

Hope this is enough info,
Cheers,
Paul

If it's a really good deal on 290 spokes it could work if you get 14mm nipples for the rear wheel. Otherwise you might not engage enough of the threads inside the nipple.

I think they'll be fine.

Hi,

Having built a few 3 cross wheels I wanted to try something different just for the fun of it.

I've got a pretty sweet price on some 290mm spokes, the front wheel is 32h, want to lace it 2 leading 2 trailing, and the rear is 36h, want to lead it 3 leadng 3 trailing.

Now, i've calculated the front to need 290.6mm spokes, so they'll be fine, but the back requires 292.6mm.

This on either side add's up to 5mm of a difference.

Will I be able to use 290mm spokes on the 36h wheel that requires 292.6mm? I'm using standard. 12mm nipples that protrude roughly 6.5mm out of the rim.

The spokes are threaded for around 10mm at the end of the spoke.

Hope this is enough info,
Cheers,
Paul

No.

If you've measured everything right, it's +/- 1mm tolerance. 290's will not work for a 292.6 (293). You will have little to zero tension on the rear, left side. Even if you tried to compensate by overtensioning the rear drive side. Do not do this.

I forgot to mention the rear hub is a single speed hub with equal diameter flanges. The same distance from the centre.

I understand you need 2 different sized spokes for freewheel hubs and freehubs. But this is a fixed fixed hub, so it's symetrical.

Reckon it'd be alright now?

I forgot to mention the rear hub is a single speed hub with equal diameter flanges. The same distance from the centre.

I understand you need 2 different sized spokes for freewheel hubs and freehubs. But this is a fixed fixed hub, so it's symetrical.

Reckon it'd be alright now?

Here's a pic I made as I do with all the wheelbuilds I do to keep me right,

http://i870.photobucket.com/albums/ab268/phesketh01/Inbred.jpg
(Btw the flange diameter in this IS measured centre to centre of opposite holes, not to the edge as pictured, that's just a quick template I made.)
The rim has an ERD of 608mm

There is no way that blue measurement is 135mm. It doesn't even include either cone/locknut on BOTH sides. That hub would fit on NO bike. And again, 290 will not work on a spoke length spec'ed for 293, regardless if it's dishless.

That's not the only thing wrong with that picture.

Regardless of the picture, the measurements I've taken are fine i made that in a hurry and clearly misplaced some of the lines.

So on a dishless wheel with a symmetrical hub, 290mm spokes wont work with 12mm nipples, for a wheel i've calculated needs 292.6mm spokes? And there's no way around it other than to get 292mm or 293mm spokes?

Is it better to round up to the nearest whole number than round down?

Regardless of the picture, the measurements I've taken are fine i made that in a hurry and clearly misplaced some of the lines.

So on a dishless wheel with a symmetrical hub, 290mm spokes wont work with 12mm nipples, for a wheel i've calculated needs 292.6mm spokes? And there's no way around it other than to get 292mm or 293mm spokes?

Is it better to round up to the nearest whole number than round down?

292 is the shortest length I would use on your rear wheel. Longer nipple will not help you, as I don't believe they have any longer threads.

You can round up or down depending on your ERD measurement. When I use the manufacturer's ERD I usually round down and when I measure the ERD myself to the bottom of the nipple screwdriver slot I round up. Rounding down by 2.6mm is too much IMO.

It's always better to round down to avoid running out of threads. This is more important on wheels on rear wheels with high driveside tension.

Generally, one would calculate the optimal length, then round to the nearest available spoke length. Depending upon the obscurity of your length requirement & spoke type & the extensiveness of your suppliers inventory, this will generally mean rounding by less than a mm, but sometimes more. 2mm off is about the maximum that would typically ever be required, and I 'd generally recommend against exceeding it.

On the other hand, you'll probably be fine. They'll reach, but you'll have a bit less thread engagement than is optimal; slightly more chance of breaking a spoke. You're going 3-leading, 3-trailing, so obviously "optimal" is not the target.

I have build very nice 3-cross wheels where I wouldn't have dreamed of being off by 2.6. I have also laced the cheapest spokes I could find to a beat-up coaster hub in the very 3&3 pattern you describe. I say, go for it.

You can do just fine with 3mm short. It just isn't the Sunday-go-to-meeting way to go.

Nope...wouldn't do it...don't use nipples as a spokes...nipple barrels will eventually break...unless you are certain that the spoke ends are getting into the rim a mm or so after final tension.

Also if those spokes are DT or Ritchey...I wouldn't be surprised if they came out of the box measuring 289.5 mm...leftover stocks of DT and Ritchey spokes from the 80s and 90s still show up with spokes .5mm under the box labelled size.

Check with a Park Tool or Wheelsmith spoke ruler...

=8-)

This link (http://www.baldurdash.org/OtherStuff/3leading3trailing.html) says that spokes for 3 leading 3 trailing wheels should be 1-2 mm longer than required, because the extra lacing in this pattern takes up a bit of length. I think 2.5mm short would normally be fine, but maybe not in this case. I have never built a wheel in this pattern.

Thanks a lot for the advice guys. 290mm is a pretty sure length to buy though, I've used them before and now again, so i'm sure i'll use them in future.

I think I would need longer spokes for the rear after reading some, it just means I'll probably end up buying some cheapo spokes cut to length instead of the double butted oens I wanted, but then again, as I said, I'm only doing this for a bit of fun and for a change. As for 3leading 3 trailing needing longer spokes, Iknow quite a few guys who have bought standard 3 cross cheap wheels and re laced them for the fun of it with no problems due to spoke length.

As was said, i'm not going for the best wheel I can build I just want a little project to work at over the break. I think I'll still get the 290mm spokes for the front and see what I can get in the mean time for the back and keep an eye out for some better spokes, and if they're cheap enough get them and relace the whee, no harm done.



Again, thanks a lot for the info guys, much appreciated,
Cheers,
Paul

... 290mm spokes wont work with 12mm nipples, for a wheel i've calculated needs 292.6mm spokes? And there's no way around it other than to get 292mm or 293mm spokes?

I might try that build if it was parts that I had on hand, but I wouldn't buy parts with such poor odds of fitting. You're basically trading out all your margin of error in the first round.

I 've had no problems compensating for shorter spokes with longer nipples though.