rosefarts

I've built maybe 20 wheels in my time.

I get the right spokes, lace em up, and tension them and they've always been fine. I usually don't use spoke prep, I just put them together. Front and rear they've been fine. Some I felt like were better wheels than others, but they all worked great and were running great and perfectly fine once I parted ways with them, usually years later. I'm not pro but I trust my wheels just fine.

So I built a rear wheel the other day and had it "finished". I went on an 8 mile ride with it and somewhere near halfway I noticed I'd basically lost all tension in the wheel. Every spoke was crazy loose. Only a few threads were connected. I even had a few spokes come undone. I'm surprised I made it home. It fell apart like a house of cards collapsing.

I have two theories as to what happened. One is that the nipples were for a larger gauge spoke than I had and weren't able to stay tight even though they felt fine on the initial build. The other is that I hadn't properly stress relieved the wheel and it got loose on the ride and basically unscrewed itself. I'm not sure. I got new nipples that I knew fit, relaced the wheels, and brought them up to tension. I rode them today and they worked perfectly. No loss in tension, no noises, no problems. Basically a finished wheel.

So to the people who've done this more than me, what the heck do you think happened?

trailangel

What spokes?
What nipples?

3alarmer 

...if you were using the wrong nipples for the wire gauge of the spokes you used, it would go a long way toward explaining this.
They make different gauge specific nipples for a reason. But if you are pulling up your tensions as tightly as you should, it ought to become obvious as you do your final tensioning.

cbrstar

Did you flex and destress the spokes before tensioning them up?

rosefarts

Of course I flexed and destressed the spokes when I built them. Maybe I didn't get them enough.

The spokes were Sapim Lasers.

I was supposed to get a set of Sapim brass nipples in the mail in a separate shipment and they never came. I got impatient and built the wheels with some brass nipples I took off a wheel I took apart a few years back. I don't know what kind of nipples they were. It was a lower end wheel with straight gauge DT spokes, That's why I think they may have been too big. It all fit and trued up just fine though, I thought I would have noticed much sooner if they didn't fit.

I was lucky it happened while I was out of town yesterday. There aren't shops open Sunday where I live, had I been home, I'd have had to wait another day to get it taken care of.

Retro Grouch 

I once worked in a shop where, sometime previously, somebody had intermixed 14 and 15 gauge nipples. Constant PITA.

cpach

If someone did that and I knew about it, I'd make sure it was their responsibility to go through each spoke to sort them out. Terrible.

davidad

The simple answer is that you did not have enough tension for the load.

Hoopdriver

It's easy to use a 14g nipple on a 15g spoke and not notice that it's not the right one. This is easy to check. Not enough tension would do it too, but probably not as dramatically as you describe.

Andrew R Stewart 

I like to insure the spokes are taking as straight a line from the flange to the rim, either side of the cross. This means for most 14 gage spokes after the initial lacing and few nipple threadings I'll press on the spoke just as it leaves the flange. This bends the elbow or adjacent spoke shaft to better follow a straight path as otherwise there's often a bulge/flair/swoosh to the spoke's path. This extra spoke length means the tension will lessen as the spoke path straightens with use. Sure enough initial tension will usually overcome the spoke's wanting to straighten on it's own but why depend on that and also maximize the break in issues. Andy

trailangel

What about the Sheldon Brown Method?

WizardOfBoz

On 10 June 1990, British Airways Flight 5390 had one of its cockpit windows blow out. The pilot was partially sucked out the window (his ankles got caught in the controls) and the cabin crew had to take turns holding him so he was'nt lost overboard. The crew thought him dead, but wanted to avoid him being sucked into an engine. Despite this, the copilot landed the plane safely, and.... the pilot lived and even returned to work 6 months later!

The error that caused the crisis was that a maintenance guy had used 8-32, and not the proper 10-32 screws. In fact, the wrong screws had been used in a previous servicing, and the service just before the flight involved a mechanic not following proper procedure and replacing "like for like" instead of checking what the actual bolts should have been.

I could see that wrong size (or inferior) nipples stripping out in service.

dsaul

Tubeless tires? I've had this happen twice with tubeless road tires. I found that the act of mounting and inflating a tubeless tire caused the spoke tension to drop by 30kgf. This was enough to allow the wheel to completely de-tension over about 10 miles. I re-tensioned the wheels with tires mounted and never had that problem again.

rosefarts

I'm going to go with almost all of the above.

I played with the old nipples, I'm pretty sure they are the right size.

I bet I didn't get enough tension to start with. Add that to the tubeless tires, and a potential loss of tension from that.

I will put both front and rear back on the stand and give them a once-over now that they've got a few miles on them and have been holding air tubeless for a week.

Retro Grouch 

If I had known who did it I would have used the dull cable cutters to make sure he couldn't reproduce.