Bicycle Mechanics - Broken spoke nipple. Anything to worry about?

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rykoala
04-23-07, 12:03 PM
The wheel is a hand built Velocity Cliffhanger 32h rim on an IRO fixed/fixed hub. The thing is SUPER strong. Spokes are 14g straight guage. I've been riding it since 9/05
Saturday while doing a bit of maintenence I noticed that the wheel was out of true. That was quite unusual, so I pulled the wheel and inspected it on the truing stand. I started squeezing pairs of spokes and quickly I found that I had not busted a spoke, but instead the wheel had a broken nipple. I have never seen that before. At least it explains that ticking sound I've been hearing from the back. I dismounted the tire/tube and pull the rim tape back. I had some extra's laying around, so I replaced the broken one. I brought it up to the same tension as the surrounding spokes, and the wheel required just a few minutes of truing on the stand with no more than 1/4" turn needed of any spoke to bring it to within about 1/64" of perfectly true. I am still confident about riding the wheel.
The real question is: Do I have anything to worry about for the future? It seems like a fluke to me, but I want to know if I need to keep a close eye on this wheel.
Thanks a lot!
Nessism
04-23-07, 12:10 PM
Aluminum nipples have a tendance to pop the heads off. Brass much less so.
You're fine. I've done the same.
The nipple may have been damaged when the wheel was built. Just watch it closely for a while. Nothing wrong with good quality aluminum nipples.
Al
Nessism
04-23-07, 07:41 PM
Nothing wrong with good quality aluminum nipples.
Nothing wrong with them other than they seize due to galvanic corrosion and the heads can pop off as they age harden. :(
rykoala
04-26-07, 10:20 AM
Thanks everyone. I forgot to reply earlier in the week to say that I have had no further problems and that the wheel is as true as when I got it, or darn close! I appreciate the assurances.
For the record, it was a standard brass nipple
For the record, it was a standard brass nipple
Yeah, you've got to watch those brass nipples.:rolleyes:
Lectron
04-26-07, 03:14 PM
...............The thing is SUPER strong. Spokes are 14g straight guage...............
An that's how i can tell your wheel is not super strong. Straight gauge.
Stresses the nipples and elbows. Stiff, yes. Strong, no.
rykoala
04-26-07, 04:40 PM
I knew someone would say that. If you can tell me that with a wheel with a 1.25" tire at 90psi at 20mph with a 330lb rider hitting a large pothole jarring the whole bike (and rider) and it still perfectly true is not in fact a strong wheel, then I don' t know what is.
Lectron
04-27-07, 12:00 AM
Straight gauge stresses the nipples and elbows more than swaged. Stiff, yes. Strong, no.
A straight gauge would take around 3000N before it starts to go plastic.
A swaged 2500. The swaged would also be 25% more elastic. They would
both have the same elbow and use the same nipple. Now you do the math
tellyho
04-27-07, 06:30 AM
I would be a little concerned about a broken brass nipple. But I'm a cheap bastard, so I'd replace and keep riding the wheel.
rykoala
04-27-07, 07:08 AM
Straight gauge stresses the nipples and elbows more than swaged. Stiff, yes. Strong, no.
A straight gauge would take around 3000N before it starts to go plastic.
A swaged 2500. The swaged would also be 25% more elastic. They would
both have the same elbow and use the same nipple. Now you do the math
There is no doubt that what you are saying is true. The wheel would be stronger with swaged spokes. There is no argument. What I am trying to say is that the wheel is plenty strong as is. If I ever break any spokes or more nipples, then I'll rebuild the wheel with better spokes. Until then, I see no need.
TallRider
04-27-07, 07:59 AM
I'd thought that rykoala was thinking that straight-gauge spokes made for a stronger wheel. Oh well. It's worth explaining why swaged spokes make a stronger wheel, for others reading this thread:
Straight-gauge are stronger in the middle (where they're thicker). But spokes never break in the middle except from direct impact (like if a derailer shifts into the spokes). Spokes break at the elbow or sometimes at the threads. And the bact that a butted spoke stretches more in the thinner center section relieves some of the stresses at the ends of the spokes, wehre problems sometimes do occur.
Anyway, I would also say, "just replace the nipple and keep riding."
I've seen brass nipples with partly broken heads. Easy enough to just replace.
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