Breaking Spoke Nipples
 

I'm building a four-cross wheel and am having a lot of problems with breaking spoke nipples--in building two wheels I have probably broken 12 or 15 nipples. They don't actually break, but the threads strip out with a loud pop at what seems to me a pretty moderate amount of tension--less than what you'd expect in a finished wheel. I've been bringing the tension up gradually around the wheel a half-turn per spoke at a time, maintaining true as I go. BANG! There goes a spoke. A few spokes further, BANG! there goes another one.
I'm starting to think that the tension is actually too high. I don't have a tensionometer, so I'm guessing on tension by the sound the spokes make when plucked. They don't sound fully tensioned to me, compared to the sound of another (presumably properly tensioned) wheel. It occurs to me, though, that this comparison wheel is spoked three-cross, so it obviously has shorter spokes. This would perhaps make the spokes give off a higher tone when plucked for a given tension? So maybe I'm tensioning the longer spokes much more than I mean to judging by sound. It's also possible, I guess, that I have a bad batch of nipples, but that seems much less likely. They're new DT Swiss nipples and spokes. I haven't broken any spokes--just the nipples.

I use DT Swiss alloy nipples and have never had a failure. Are you deforming the nipples with the wrench? What kind of wrench are you using? Does it hold the nipple on all 4 sides? Are you lubricating the threads? If not, try that.
A Park tension meter at $55 to $60 is an excellent investment.

Al

14g nipples on 15g spokes?

How many spokes?

More crosses doesn't necessarily make a stronger wheel. You want the spoke to be at a tangent to the hub and as near perpendicular as possible to the rim. Too many crosses makes the spoke enter the rim at too much of an angle. 4 cross generally works best with 40 spoke wheels.

I'm using a red Spokey wrench that engages the nipples on all four sides and is the correct size--no deforming of the nipples. I've been lubricating the threads with linseed oil.

Hmmm... exactly the wrench I use. I would look to "cavernmech's" question. Do the spokes match the nipples?

Al

+1

Hmm, well, I ORDERED 14-gauge spokes and nipples. I've been assuming that that's what I was sent. I don't see any markings on either the spokes or the nipples, but I can say that until the moment of failure, the nipples seem to thread on correctly with no sign of the slop I'd expect if there was a threading incompatibility. Any ideas on how to check this for certain.
To answer another question, it's a 36-hole rim. I went with four-cross because I'm using a hub that had been previously built up in a four-cross pattern.
JV

+2

I've done this myself. Try screwing them on a larger gauge spoke if you have one. That's when the light bulb came on for me.

It may be time for that tensiometer.

Are the spokes long enough ?

Another very good question. How many threads are you engaging before you actually start tightening? I'm always able to cover the threads completely with the nipple before I even start the truing phase. If you can't do that your spokes may be too short - if you're lucky you might be able to get away with buying longer nipples.

thats what im smellin

That sounds like a good way to run out of threads before reaching the target tension.

Never happened to me. Not a pro, but I've built about about half a dozen wheelsets in the past couple of years - radial, 2X, 3X.

Unlike body parts, with spokes it's better to be a little short than a little long.

Al

breaking spoke nipples
 

Actually, I've concluded that the spokes ARE too short, by at least 2, and maybe 3, millimeters. When the spokes are tight, there are still 5 or 6 threads exposed in some cases (in others more like 2 or 3). I think that's the problem.
That raises another (to me, at least) interesting question: do you just have to accept the fact that when you're building a wheel with a given hub and rim, there's a substantial chance that you'll start with the wrong spokes? I ask because I consulted several different spoke calculators, which gave lengths that varied, as I recall, by about a millimeter or more. For no good reason, I finally went with the Spocalc length, which called for, as I recall, 300.6 or something for the front wheel and non-drive side rear, and 298.3 for the drive side. The DT Swiss calculator was quite a bit shorter. I rounded down, not wanting to run out of threads too soon. As it turns out, I would have come up short even if I'd rounded UP.
So what's a wheelbuilder to do? Once you find a combination that works you can obviously build the same wheel successfully again and again, but for a first try it seems to me that you have to choose a spoke calculator based on educated guesswork, round up or down based on a guess with no data, buy the spokes, and hope for the best. I'd guess that people must come up wrong pretty often. Is that the case?
I'm going to try again with new spokes. At least now I have a good handle on what the actual length needs to be.
JV

I've always used Spocalc and haven't run into problems, but I've never tried 4X lacing, so I don't know if that's an issue. Did you make the measurements yourself or depend on their inputs? I always doublecheck the hubs with my own calipers - but the biggest place to make a mistake is in the ERD. If you measure it yourself you may not be doing it correctly.

breaking spoke nipples
 

I measured the old Campagnolo hub myself but used Spocalc's input for the new Mavic rim.
JV

I'm thinking there was a problem with the hub measurement, assuming you set up spocalc with the 4x instead of default 3x. Getting the crossing wrong would have you too short too.

I, like you, am not a pro, but I've built around 20 wheels using spocalc, and only two of those wheelsets were repeats. I've also always gotten agreement between spocalc and DT Swiss' calculator.

This would be my next guess, that you thought you were pulling the 4X numbers but really used 3X. If you'd like, throw out your hub and rim combination and I'll run it myself.

Breaking Spoke Nipples
 

I ran it for both 3x and 4x and noted both. 3x and 4x are so different from one another that it would be impossible to mix them up. I just checked my notes--for 4x I came up with a front hub spoke length of 300.1 (vs. 288.9 for 3x). For the rear wheel, I came up with 298.7 on the drive side (vs. 287.5 for 3x) and 300.7 on the non-drive side (vs. 289.5 for 3x).
My notes on hub measurements for the front: D=67, S=2.6, A=16, B=16, WL=34, WR=34.
For the rear hub: D=67, S-2.6, A=25, B=46, WR=17, WL=38. I haven't run the numbers again myself--I haven't had the heart to, and now I know what size I need based on direct measurement of how short the current spokes are. But obviously, it would be nice to now what I did wrong for future reference.
JV

That sounds so frustrating. Sorry you had this hiccup in your first wheelbuilding experience. It only gets better from here!

At this point why don't you lace them 3X. I doubt that you will have any problems with the hub. Be sure you have the short spokes on the driveside.

Al

Breaking Spoke Nipples
 

When I posted the hub dimensions and spoke lengths, I forgot to mention that the rim are Mavic Open Sport 700C.
JV