une_vitesse

so i thought today would be a nice day to ride my fixie. I built her wheels about two years ago, and haven't had any problems with them... they stayed true, till today: i got on the bike, and noticed my front wheel rubbing on the brake pad.
these are built with 36, dt swiss db 2.0-1.8 3x spokes and nips, on formula hubs and nicer alex rims (the ones with eyelets), evenly tensioned at around 125 Kgf. at first i thought the spoke broke, but turns out it was the nipple. the flange separated from the rest of the nipple. keep in mind, i haven't ridden these wheels in a while, and when i put the bike away, everything seemed kosher.
has anyone had this experience? is the tension too high? and if so, why did the nipple and not the spoke fail? do i chalk it up to a defective nipple, or should i consider dropping the tension a little bit?

Panthers007

125Kgf is on the high-end of the scale (80 - 120Kgf). But I doubt that alone would be the cause. I'd be looking at the nipple being defective first and just replace it. If you can drop the tension down to 120 or so (got a tension-meter?), you could do that too. But you've ridden the wheel for 2 years, yes? With no trouble? The evidence points to a bad nipple. I rode a set of wheels I never checked the tension on until recently. It, too, had DT spokes that were 14g straight. It was ridden for about 10 years with no trouble. And it was at 125kgf front-wheel. And 155 kgf rear drive-side! Never had a gauge around until a little while back when I went back into wheelbuilding.

Imagine my surprise! I retired the set. Mavic E2 Module rims and Campy Record hubs.

wmodavis

"has anyone had this experience? is the tension too high? and if so, why did the nipple and not the spoke fail? do i chalk it up to a defective nipple, or should i consider dropping the tension a little bit? "

You didn't say what type of nipple - aluminum or brass. I'm going to guess you have aluminum. I have not personally experienced that but in my reading what the wheelbuilding pros say it is not that uncommon and the very reason many of us prefer brass nipples. They are stronger and less likely to catastrophically fail. In aluminum nipples there is also also a quality difference between older and softer al nipples and some of the better quality newer al nipples. You mentioned they were DT nipples. They make both brass and aluminum but likely they are the better quality al since they art DT.
In reality at this point it's pure speculation what really caused it but I'd replace it with a good quality similar type nipple and leave the tension alone. High even tension makes for the most durable and strong wheel. Sometimes bad things happen to good people.

Panthers007

If he just used DT spokes and standard nipples - he has brass ones. It's what DT supplies unless you specify otherwise. So builder - brass or aluminum? And yes to ^^^. 125Kgf is fine in my experience. I was trying to get that across. LOL.

une_vitesse

thanks all! wmod, i used brass nipples and yeah panthers, i do have a tension-meter. i will proceed with my initial plan, which was to replace the offending nipple, ride on and hope it doesn't happen again!

TallRider

I'd agree, it's likely a defective nipple. You could make a t-shirt out of it: "I had a defective nipple"

One thing mechanically, is that there's little reason to max out the tension of the front wheel. Putting rear drive-side spokes to maximum safe tension is important, because it means the non-drive-side spokes are less loose (and loose spokes can become looser over time and end up breaking at the elbow).
The front wheel is not dished (except in disc brake cases) nor do the spokes carry any torsional load. So there's little harm in putting the spokes at somewhat lower-than-max-safe tension.
Heck, on a fixie or singlespeed, the rear wheel usually isn't dished much, although the spokes do carry torsional load.

But none of this is very important, because brass nipples rarely fail like this. The rim cracking is usually the limiting factor for excessive spoke tension.

Al1943

Probably a defective nipple. I routinely run 157 kgf on DT aluminum nipples and have never had one break.

daveornee

How did you lubiricate the threads and the rim/nipple interfaces?
I have seen nipples damaged by dry threads and/or dry rim/nipple interfaces.
125 kgf is high tension, but I doubt that 125 kgf tension by itself is the cause.

une_vitesse

i dipped thespoke threads in tenacious prior to acing, and dropped some triflow in the nipple eyelets before bringin up the tension.
the crazy thing is that the bike was sitting for like a week... mebbe it was jealous of my other rides. anyway, i removed the broken piece in the rim and replaced the nip and trued the wheel. so far, so good.
again, thanks for the responses