[Will_Jekyll]

I broke two spokes on my rear wheel yesterday, one drive side one brake side. I broke one on the drive side about a month ago. Could it be I need stornger spokes or is it more likely to be a bigger problem? The wheel is a 32 spoke cannondale expert rim and hub with DT Champion stainless spokes. Also I have disc brakes.

 

[Tenchiro]

Who built your wheel?

 

[Will_Jekyll]

The wheel came with the bike and the last time I broke a spoke I got it fixed where I bought it, Big Ring cycles in Golden. This time I took to a different shop.

 

[ohio]

Have the wheel trued and tensioned by a good wheelbuilder. That should solve your problem. They're probably just throwing new spokes in there without checking the tension on the rest of them.... idjits. I'd get a new shop or make sure a real mech is working on the bike.

 

[JohnMc]

Robot built wheels (most OE wheels) sometimes have uneven spoke tensions.

Check the overall tension by lightly 'pinging' each spoke with something light and hard. You can get an even spoke tension by ear - or at least spot something out of whack. While a rim can be true with uneven spoke tension, it will come out of true easily and the tighter spokes will tend to break easier. (Note - only compare one side to itself - the drive/non-drive and dis/non disc sides have different tensions)

My own wheel truing procedure:
- even all spoke tensions
- fix up-and-down
- fix side to side
This prevents me from chasing problems with more and more uneven spoke tensions.

Even with proper tension the spokes eventually fatigue and fail. If you have a lot of miles on your wheels they might just be worn out. The looser they are the quicker they seem to fatigue.


You might try some Spinergy wheels with the 'plastic' spokes too - I've abused a couple of sets of those (one Spox set, currently have Xyclone discs) mightily with out ever having them go out of true or break a spoke.

 

[bomberz1qr20]

Well here's the deal, you can repair a wheel easily by replacing the broken spokes and re-tensioning and stress relieving the wheel...cool.

However, this does not solve what has already happened to the wheel. It has probably suffered from too little tension for it's lifetime so far. This is what breaks spokes. As a wheel encounters forces (weight, bumps) the spokes loses a small an amount of tension momentarily. Over time these minute cycles of tension loss and gain put fatigue on the spoke at the elbow. That's why spokes sometimes don't even break from an event or impact, they just break whenever. As they break it throws the tension of the whole wheel off, and after replacement the whole wheel should be de-tensioned and re-tensioned carefully to restore the balance.

Proper wheel tension helps the wheel to resist the tension loss from impacts and general harsh conditions found in trail riding, giving the wheel a longer life. So the end result may be that your wheel has gone too long with not enough tension, and the spokes are fatigued to the point of failure. A re-build may be helpful if the components are still worthy. Have a reputeable (sp?) builder look 'em over.

 

[Will_Jekyll]

I e-mailed Sheldon Brown and he told me to have the wheel relaced with all new spokes also. So I called up the bike shop and told them to relace it with all new straight gauge spokes. Thanks for the quick responses.