Spoke broken - how come the rim has "twisted"?

pianoman

I snapped a spoke last week and, as it was under warranty, took the wheel into the shop I bought it from. The spoke has been replaced but apparently it's resulted in "the rim being twisted" (I presume buckled). I suspected this was the case when it was wobbling around with the brake off on the last few miles home last week, but never expected the damage to be quite so unrepairable.

My point is; can I expect this every time I break a spoke? Or is it a function of wheel design/spoke count? The wheels have 24/28 spokes front/rear. And is this problem magnified with lower spoke counts, such as those found on Mavis Aksiums and Fulcrum 7's? Or is it down to the amount of tension in the spokes? I don't ever recall seeing the spoke tension gauge for these wheels.

stoobydale

Yes, the combined high tension on factory wheels and a low spoke count do result in a big buckle with just one spoke breaking. usually not terminal though with just one spoke gone. find a local wheel builder and ask him to have a look at it.

pianoman

I wouldn't have thought 28 is a low spoke count nowadays though? I guess what could have magnified the problem was the fact that the tension is at the (internal) nipple, and that's where the spoke snapped, rather than in the middle? Or could it be that the wheel was not properly tensioned to begin with (it was a factory wheel not handbuilt) and that the snapped spoke was the straw that broke the camel's back?

Is there any way of ensuring my next wheelset doesn't suffer from the same problems? Should I look for a deeper rim, more spokes, or both? Or should I ask the shop to check the spoke tension is correct before buying, even if it means giving them a few quid extra?

stoobydale

Spokes rarely break in the middle, usually at the head or nipple as in your case. 28 isn't a particularly low count but there is still a fair gap between the other spokes when one breaks, therefore more chance of a bigger buckle. Mavic wheels are highly regarded but I have seen and heard of a lot of cases of broken spokes. personally I like Campagnolo wheels if I am buying factory built however I now build my own and would go handbuilt everytime nowadays.

geoff_ss

A wheel has (at least) two stable conditions as I learned to my cost many years ago in the Spanish Pyrenees.

We were having difficulty finding both a campsite and anywhere to buy food. In a fit of childish pique I picked my fully laden bike up turned it round and banged it down on the road. When I tried to wheel it along it wouldn't move. The rear wheel had adopted an pretzel shape and wouldn't clear the brake blocks - Panic! I took the wheel out and straightened it by leaning it against a lamp post and applying gentle pressure. With a ping it sprang into its proper shape and I had no further problems (other than finding the campsite etc ...)

So, it could be your wheel has done the same thing. I've experienced broken spokes on both tandems and singles but never suffered permanent damage to the rim as a result. In fact very early on a tour a friend broke a spoke in a 36h rim and rather than going to the trouble of removing the block I just re-trued the wheel with 35 spokes and she had no problems for the rest of the week's cycling.

Monty Dog

Depends on how far out the rim was and whether it was creased or distorted. I've straightened some big buckles in my time with no longer term effects but you need to effective true the wheel to get the rim straight and then slacken and retension all the spokes evenly like a new build. Shops often don't have the time to do this and would rather flog you a new rim and rebuild as it's easier.

dennisn

Monty Dog wrote:

Depends on how far out the rim was and whether it was creased or distorted. I've straightened some big buckles in my time with no longer term effects but you need to effective true the wheel to get the rim straight and then slacken and retension all the spokes evenly like a new build. Shops often don't have the time to do this and would rather flog you a new rim and rebuild as it's easier.

Most shops don't really want to work on a wheel that they feel may be bent, cracked, or badly distorted. It's the same old story, you want it fixed, but it may not be fixable. Then a few weeks later it fails and you're pissed off at the bike shop. Which doesn't do them any good. I understand why they may refuse to FIX something, without using new parts.
It could be their way of selling stuff, but more than likely they don't need the bad publicity,
so to speak.