Broken Spokes

I had this issue a few months ago, but both of mine broke when I wasn't even on the bike!?  

Had the thing rebuilt and checked and since then (~1000miles) no problems!

I would guess that once one goes, there is a significant amt of strain put on other spokes, thus weakening them to the point that they could break....   I don't think that the added pressure from the tire would impact that all too much... an additional 5 psi, with no outward constraints, shouldn't exceed the safety factor...

Where did they break?  at the nipple?

Yes both have been at the nipple.

My guess is that the spokes were too loose.  Without enough tension, they'll have some play and any movement can easily shear them off at the nipple.  You said you had the wheel trued and my guess is that in getting the wheel trued, the tech took the easy way out by loosening on some rather than going for the spec tightness all around and then trueing by tightening.

I had something similar recently.  First, one broken spoken, with several loose ones.  Got that fixed, then a few weeks later, 4 broken spokes!

It's a very old wheel, so, that may have something to do with it.

This is true. When one goes it yanks significantly more on the others. The common mantra is 'when one goes another is more likely to go'. A totally helpless feeling, but I broke one last year 40mi away from home. There really is no sure way to tell. But a check by a mechanic is definite.

Spoke update...I took it to the LBS today and they said as 2 had gone in just over a week it was a fault with the Bontrager wheel so they are hand rebuiling the wheel for free!!! 

They will then claim it back from Trek, apparently it happens more often than you realise! Oddly though the wheel is 4 years old so I don't think it has a guarentee unless Trek offer a lifetime one that I didn't know about.

Either way win win for me!

Edited by Bob the Trier! 2009-08-25 6:00 AM

I've got to stand up for my former profession. I doubt very much that the mechanic loosened spokes.

The most likely cause was having factory built wheels. Aside from high end wheels, most factory wheel built wheels are always under tensioned. Riding them like this will weaken the spokes. Then when one breaks and is replaced, the mechanic will do his job and tighten the wheel to the correct tension and it will start breaking spokes often. Once you've break several spokes in a short time period, assuming there was no outside influence like large pot holes or something getting caught in the spokes, the only answer is to rebuild the wheel with all new spokes.

This is one of the reasons I very rarely buy factory built wheels. I've never had issues with wheels I've built and tensioned properly. I've had nothing but issues with tension with factory built wheels*.

*I'm not talking about high end wheels like Zipps or high end Mavics, but mid to low end factory built wheels.

my LBS is trying to get my less than a year old, (probably 48 weeks) Bontrager fixed under warranty as well- I haven't heard back from the LBS yet, it's been about 2 weeks. If it's a 1 year warranty, I should be good unless they claim misuse.