Broken spoke

[foxyrider]

I suffered this malaise a couple of weeks ago, a single spoke going ping very audibly as i made a 25% decent off the Cotswolds! 32 now a slightly wobbly 31 spokes which transported me the remaining 25km home without too much problem.

The unusual thing was, that when i came to sort it out the next day, the head of the spoke was still in the hub (the break was in the J bend). So here is a rare view of both parts of a spoke that has expired on the bend.

Not a brilliant pic i know but i thought folks would be interested to see it. The bright spot was the final break so it looks like it was hanging together essentially 75% failed for some time, the extra braking forces finally causing failure.

[alexnharvey]

Very interesting. Do you know how any miles approx before failure, i.e. was it premature or had it had a good working life? Was it a leading or trailing spoke? Was the spoke well bedded in the flange or was the elbow slightly too long (as is commonly the case these days).

[foxyrider]

Very interesting. Do you know how any miles approx before failure, i.e. was it premature or had it had a good working life? Was it a leading or trailing spoke? Was the spoke well bedded in the flange or was the elbow slightly too long (as is commonly the case these days).

For clarification its a Tiagra hub with an Alex rim, a Raleigh machine build, I had to replace 2 spokes in the same wheel last year, they failed within seconds of each other in a similar steep descent/hard braking fashion. Previously it hadn't been touched from new.

The wheel is @ 10 years old although most of its mileage has been accumulated in the last 18 months (@ 20k kilometres), the matching rear has been retired with a worn out rim but never had a spoke breakage. Is that a good life? It gets used on everything from smooth tarmac to unmade byways and everything in between so not an easy life, i certainly don't consider that it owes me anything.

The spokes do seem to be well bedded, the broken bit needed some assistance to be removed! being a front wheel it has been used trailing and leading but i think it was leading when it failed.

[willem jongman]

Whether this is premature or not is immaterial. Once three spokes have broken, it is time to rebuild the wheel because the remaining spokes will have been stressed too much. At that moment it is obviously a good idea to see if the rim has enough remaining life in it as well. There is not much point in spending on a wheel rebuild if the rim is approaching the end of its life as well.

[Vorpal]

The fatigue life will be similar for the spokes at the same stress. So, it somewhat depends on the lacing pattern, but all spokes in similar positions to the failed spokes are likely to fail the the relatively near future. As Willem has noted, additional stress may have been induced by the failures that have already occurred & that additional stress could accelerate failures.

I would rebuild or replace the wheel at this point.

And IMO, 20k kilometres is a good life, and more than I have ever gotten from a wheel.

[rogerzilla]

Plain gauge spoke?

[foxyrider]

Plain gauge spoke?

yep

[foxyrider]

The fatigue life will be similar for the spokes at the same stress. So, it somewhat depends on the lacing pattern, but all spokes in similar positions to the failed spokes are likely to fail the the relatively near future. As Willem has noted, additional stress may have been induced by the failures that have already occurred & that additional stress could accelerate failures.

I would rebuild or replace the wheel at this point.

And IMO, 20k kilometres is a good life, and more than I have ever gotten from a wheel.

Already thinking along those lines, will probably buy another wheel and pension this off as emergency spare, the rim looks to have some life left but the cost of new spokes is as much as a like for like wheel!

[alexnharvey]

Whether this is premature or not is immaterial. Once three spokes have broken, it is time to rebuild the wheel because the remaining spokes will have been stressed too much. At that moment it is obviously a good idea to see if the rim has enough remaining life in it as well. There is not much point in spending on a wheel rebuild if the rim is approaching the end of its life as well.

It really depends what the question being asked is, or if one is being asked at all. If (as you have assumed) a question was being posed as
to whether or not to rebuild the wheel given that 3 spokes have failed then you have a point although I would argue if it's only done 100 miles the answer will be different to having done 100,000.

It seemed to me thought that foxyrider was not seeking guidance on whether to have the wheel rebuilt but was making a post of more general technical interest on spokes given the previous discussions here. However, maybe I am the one inappropriately abbreviating assumptions .

[531colin]

Another approach is to stress-relieve the wheel thoroughly.
A few more spokes which are already cracked may fail.
After this, maybe 2 or 3 more may fail in use, but most will usually be OK.

[NATURAL ANKLING]

Hi,

Another approach is to stress-relieve the wheel thoroughly.
A few more spokes which are already cracked may fail.
After this, maybe 2 or 3 more may fail in use, but most will usually be OK.

I think this is not the first time that the problem by foxy for that wheel has been posted.
Same advice last time by Brucey IIRC.

[foxyrider]

Hi,

Another approach is to stress-relieve the wheel thoroughly.
A few more spokes which are already cracked may fail.
After this, maybe 2 or 3 more may fail in use, but most will usually be OK.

I think this is not the first time that the problem by foxy for that wheel has been posted.
Same advice last time by Brucey IIRC.

Wasn't looking for any advice - it really was an 'out of interest' post as i've never in 40+ years had both parts of a spoke that has broken at the elbow. Each time spokes have been replaced the wheel has been stress relieved - its already done @ 1000km since this latest breakage! As i mentioned earlier, i am looking at retiring the wheel soon anyway, if it starts shedding more spokes that will get brought forward.

[NATURAL ANKLING]

Hi,
How well does the spoke fit the hub?
Just curios.
Is there any space under the bend?

[rogerzilla]

The elbow takes more punishment in plain gauge spokes than in butted ones, which have a bit of give in the thinner middle section. This is why they last longer, although even butted spokes usually break at the elbow too.

[531colin]

Hi,

Another approach is to stress-relieve the wheel thoroughly.
A few more spokes which are already cracked may fail.
After this, maybe 2 or 3 more may fail in use, but most will usually be OK.

I think this is not the first time that the problem by foxy for that wheel has been posted.
Same advice last time by Brucey IIRC.

Wasn't looking for any advice - it really was an 'out of interest' post as i've never in 40+ years had both parts of a spoke that has broken at the elbow. Each time spokes have been replaced the wheel has been stress relieved - its already done @ 1000km since this latest breakage! As i mentioned earlier, i am looking at retiring the wheel soon anyway, if it starts shedding more spokes that will get brought forward.

Not properly, it hasn't