Broken Spokes - When to give up on a wheel?

[User6179]

Naming the spokes as trailing or leading doesn't help since a trailing spoke could be either outbound and inbound. It is only the latter that makes a material difference how the spokes are configured in the hub and the angle at which they're bent. Although a trailing and leading spoke undergoes cyclical stresses in different ways, this makes no difference. They both fatigue at the same rate. I'll explain. Let's assume the spokes on the left side are tensioned to 1000N. When pedaling, torque at the hub causes all the trailing spokes to increase tension and all the leading spokes decrease tension. It may help to visualize this by calling them pushing and pulling spokes. Even the strongest rider in a sprint produces only enough torque to increase/decrease that tension by 5%, in a wheel with 32 spokes. 5% up or down in a part of the spoke's strain graph that falls far short of the yield curve has no material effect on metal fatigue in steel. In other words, they all fatigue at the same rate.
Now back to your example. A poorly-built wheel will not have been stress-relieved and the base-line I mentioned in the previous post would not have been eliminated. Since one set of spokes are bent at the elbow more than the other set, the set with the more acute angle will fatigue faster. I'm sure this is what happened to your wheel but I can't say for sure because I don't know whether these were inbound or outbound spokes. Perhaps you can check and let us know.

As for the second example: sharp ridges in hubs where spokes exit are a big contributor to spoke fatigue. The use of soft aluminium hubs and stress relieving eliminates this problem in well-built wheels. I will be so bold as to say that your anecdote holds true for that wheel only and a general case can't be made.

They are outbound spokes

 

[EasyPeez]

Yes I did say that but then you said the wheel is cheap and you don't want to spend money. It will be cheaper to buy a second hand wheel, especially since the new fad is 29" bikes and 26" ers are abandoned 'cause they're out of fashion. This will get you going quickly and cheaply and you won't have to doubt the builder's skill.

Nice one, thanks

 

[w00hoo_kent]

When I asked about wheel rebuilds (remove all spokes, replace, re-true) my LBS quoted me around £60 and inferred they didn't really want the work. I ended up putting the £60 towards the new wheels. A straight replacement wheel isn't particularly expensive, I'd guess it'd be under that £60 going like for like on a BSO.

 

[Yellow Saddle]

They are outbound spokes

OK, that explains it. The original builder did not stress relieve the spokes or corrected the spoke angle at the hub after lacing. Those will be the first to go as you correctly observed. However, the other set is following on the heels of these ones and will start to fail shortly after. I'm totally sure about this because stress relieving involves all the spokes simultaneously, or in pairs that cannot isolate inbound from outbound.
Technically all the outbound ones will fail first and then the inbound ones but statistically and practically this is not how it will pan out. Hence my advice to replace all.

 

[Yellow Saddle]

When I asked about wheel rebuilds (remove all spokes, replace, re-true) my LBS quoted me around £60 and inferred they didn't really want the work. I ended up putting the £60 towards the new wheels. A straight replacement wheel isn't particularly expensive, I'd guess it'd be under that £60 going like for like on a BSO.

Although I haven't worked in the UK and have never purchased spokes here, BP60 indicates that the shop didn't want the job and attempted to price you away or towards another, easier option. It also indicates to me that the wheelbuilding skill is disappearing. In my estimate the job, for silver spokes (black is 20% more expensive) should be about BP40. Keep in mind I have no idea of local pricing and am basing my estimate on wholesale prices I enjoyed in a different country.

 

[User6179]

OK, that explains it. The original builder did not stress relieve the spokes or corrected the spoke angle at the hub after lacing. Those will be the first to go as you correctly observed. However, the other set is following on the heels of these ones and will start to fail shortly after. I'm totally sure about this because stress relieving involves all the spokes simultaneously, or in pairs that cannot isolate inbound from outbound.
Technically all the outbound ones will fail first and then the inbound ones but statistically and practically this is not how it will pan out. Hence my advice to replace all.

The rim is worn at braking surface anyway so whole wheel will be binned once the salt is off the roads and new wheel put it on .
Sorry to OP for hijacking the thread.

 

[shadow master]

Hi,

I'd never had a broken spoke in my life until late last year. Now I've had 3 in 3 months. Does this suggest it's time to get a new wheel or should I persevere with getting on spoke at a time changed? I'm only 10stone in weight and carry a backpack with a few bits in, so not sure why this is happening all of a sudden?

I am riding a 14 year old £200 MTB that has been stuck in a shed for the last few years doing very little, then getting hammered 15miles+ a day on bad roads in all weathers and jumping off kerbs etc every day since last summer. So I guess maybe cheap wheels + long period of abuse (I never used to clean or lube it at all I'm ashamed to say - ironically I'm doing that weekly now and it's only now that the problems have started!) + long period of disuse + lots of hammer = this is inevitable? Or could it be something myself or my LBS is doing wrong?

I'd like to learn how to fix this myself this year, but for now I have neither the required tools or know-how, so have been getting my LBS to do it. Could it be that they're not truing it properly after fitting new spokes, hence the continued breakages?

I'm picking up my new Genesis at the weekend (weather permitting) so if there's anything I can do (other than look after it a whole lot better!) to avoid similar problems with that bike please let me know!

Cheers, Andy

Simple maths really a complete alloy wheel with alloy hub is £24.99....so you only have to have 3 trips to have one spoke at a time,and you're probably already out of pocket,and you got about 30 spokes left to go!

 

[EasyPeez]

Sorry to OP for hijacking the thread.

No apology needed, I got my basic answers and your extended discussion has been educational.

For anyone who's interested, I chatted to my LBS just now and am taking the wheel in tomorrow. He agreed that 3 spokes going in 3 months is a bad sign and said that he'll put a new spoke in for free to get me back on the road but if I can leave it with them all day he will look at the wheel and see if it needs re-tensioning, if there are any probs with the rim etc and then advise on whether it'll be cheaper for him to source a new wheel or re-build it himself with new spokes.
He said the re-build would take 2 days (am assuming that includes him breaking off to attend to other minor jobs as they come in) so my guess is this is not likely to be a cost-effective solution for such a duffer of a bike.

Simple maths really a complete alloy wheel with alloy hub is £24.99....so you only have to have 3 trips to have one spoke at a time,and you're probably already out of pocket,and you got about 30 spokes left to go!

The 3 spokes will have cost me £4 in total, so I'm still winning for now over the cost of a new wheel, but I agree that it's looking like I should cash in my chips sooner rather than later. £25 sounds better than the £50 I was expecting.

 

[Spoked Wheels]

The g

Although I haven't worked in the UK and have never purchased spokes here, BP60 indicates that the shop didn't want the job and attempted to price you away or towards another, easier option. It also indicates to me that the wheelbuilding skill is disappearing. In my estimate the job, for silver spokes (black is 20% more expensive) should be about BP40. Keep in mind I have no idea of local pricing and am basing my estimate on wholesale prices I enjoyed in a different country.

The going rate for wheel building is around £60 per set, only labour. £40 to rebuild a single wheel.

Some builders would only rebuild their own wheels, others won't touch factory built wheels. Not as straight forward to get a wheel rebuilt really.

 

[shadow master]

The g

The going rate for wheel building is around £60 per set, only labour. £40 to rebuild a single wheel.

Some builders would only rebuild their own wheels, others won't touch factory built wheels. Not as straight forward to get a wheel rebuild really.

I rest my case! £24.99 whole new alloy rim/alloy hub wheel complete! Baring in my we are talking about a 14 year old sub £200 bike!

 

[Yellow Saddle]

The g

The going rate for wheel building is around £60 per set, only labour. £40 to rebuild a single wheel.

Some builders would only rebuild their own wheels, others won't touch factory built wheels. Not as straight forward to get a wheel rebuild really.

Thanks for that. I'm astonished! BP 60 for a 40 minute job?
Perhaps now is the time to reprogram my computer's $ key to a £ key. How do I do that?

Edit: I just saw "per set". Still steep.

 

[Spoked Wheels]

Thanks for that. I'm astonished! BP 60 for a 40 minute job?
Perhaps now is the time to reprogram my computer's $ key to a £ key. How do I do that?

Edit: I just saw "per set". Still steep.

Set your keyboard as a UK keyboard and that should get you the £ symbol.

It takes me a bit longer than 40 minutes to build a wheel but then I'm not trying to beat any records just to build the best wheel I can

I don't know if that is too expensive or not. I had a plumber in the house the other day to fit a shower and it was 25 minutes including the coffee - £30 which I was happy to pay.

 

[PatrickPending]

I always say when one goes the rest will soon follow - on cheaper wheels anyway - what I'd do is either get the whole wheel re-spoked with quality stainless steel spokes, or buy a well made wheel. With the old wheel buy a spare spoke and have a go at fitting it yourself - for practice - replacing a broken spoke and truing a wheel. Always amazes me that people pay £10 for a single spoke to be replaced - especially when the rest will probably follow.....

 

[Ed no-more-lemons]

Got half way though the above, now off to replace a driveside spoke for tomorrows commute. Just one of those things on cheaper and or older wheels, I don't regret getting a good spoke key and having a go as it does not have to be all that time consuming after the first few replacements and on an old throwaway MTB wheel you having nothing to lose. There is a lot of truing advise online, However theres not all that much to it with a little experience and confidence. 'Dishing' however, just have not got around to that.

 

[S.Giles]

Roger Musson's wheel-building book is a great way to de-mystify the subject. It takes a little concerted effort at first, but I will never need anyone to build me a wheel having learned to do it myself.

I just re-built my front wheel because the hub was failing and needed replacement. I didn't get it done in 40 minutes though (it took me several hours, in fact).

Total cost to re-build the wheel with a Shimano hub (purchased second-hand but unused on Ebay) was £10 + time.

Steve