Yet Another Cycling Forum

General Category => The Knowledge => Topic started by: quixoticgeek on November 16, 2019, 10:14:16 pm

Title: When a spoke breaks...
Post by: quixoticgeek on November 16, 2019, 10:14:16 pm

Had a drive side spoke break on the rear wheel today, 50k into a 200. I bent it out the way behind another spoke, and continued, taking it easy and trying to avoid any bumps.

I'll take it to the vet on Monday (who's already aware, having seen the photo on social media).

But it's got me wondering, when a spoke breaks, what is the thought process on to scratch or not? This was on a 32 spoke wheel. I'm on disk brakes with a big clearance, so a wheel can go out of true by quite a bit before it's an issue.

What would increase the risk of a catastrophic failure potentially writing off the frame, chain set or rear mech?

Thanks

J
Title: Re: When a spoke breaks...
Post by: Ivo on November 16, 2019, 10:24:44 pm
When a spoke breaks I stop at the first convenient spot and change the spoke.
With my current wheel (Velo Orange hub) I can disassemble the hub without tools. For other hubs I'd use my Hypercracker (the next best thing does the same job, Marten sells them).
Spare spokes I've attached to my frame.
Title: Re: When a spoke breaks...
Post by: grams on November 16, 2019, 10:58:31 pm
What would increase the risk of a catastrophic failure potentially writing off the frame, chain set or rear mech?

If you've got 31 other good spokes, I'm going to say zero. You may lose other spokes after the wheel rebalances itself, and if you lose too many the wheel will eventually be too short of tension it tacos, but not from losing just one.
Title: Re: When a spoke breaks...
Post by: Kim on November 16, 2019, 11:00:10 pm
My touring bike has spare spokes attached to the frame.  Because it's over-engineered, I've never had to use them.

My hybrid has (or had?  I can't remember) spare spokes for the wrong wheels attached to the frame.  I once unsuccessfully tried to burgle my way into our house with one when the door lock malfunctioned.

I carry a FiberFix in my toolkit.  I've never had to use that, either, but I saw one save the day when someone on a FNRttC with a low-spoke-count bling wheel hit a pothole of doom, and decided it was a pretty neat idea.

Last time I actually broke a spoke was due to a derailleur-vs wheel incident caused by entanglement with a low-flying Tesco bag (the bag was unhurt).  I was about 200m from home, so I picked up the bike and carried it.  The drivetrain destruction made the spoke breakages academic, but if I'd been in the sticks I could probably have bodged it up as a single speed with no rear brake.

Prior to that, breakages were on cheap factory wheels or BSO-grade kit, before I was in the habit of cycling more than a few miles.


If repair isn't an option, I'd probably continue with a single broken spoke if the wheel was still functional, and I wasn't going to end up in a risky situation.  As soon as the second spoke breaks, I'd take that as a warning that the whole wheel is about to self-destruct, and proceed directly to the nearest bike shop / railway station / whatever as appropriate.
Title: Re: When a spoke breaks...
Post by: Paul H on November 16, 2019, 11:46:02 pm
I'd see if I could true it up using the spokes either side, having 36 to start with makes that easier, it'd have to be pretty bad before I considered it a reason not to ride. 
The question I'd be asking is not what to do if it happens again, but how to reduce the chance of it doing so. 
Title: Re: When a spoke breaks...
Post by: Brucey on November 17, 2019, 01:27:17 am
if a NDS spoke fails in a modern 10/11s wheel then one or more of the spoke crossings on the drive side comes slightly further to the right and this means there is an increased  risk that the RD will end up in the wheel if you use bottom gear.

 There is a similar risk if the wrong one of a DS spoke pair fails; if an 'inside' spoke from the driveside fails the outside spoke that crosses it is pulled straighter than normal and this again decreases the clearance to the RD in bottom gear.

So if you break a spoke and carry on then I would suggest that you make a point of avoiding use of the largest sprocket.

FWIW I carry kit to repair a broken spoke (which I have not had to use for decades) when I'm touring but I don't bother the rest of the time. I've found that  provided I'm riding on wheels that I've built myself, I'm extremely unlikely to break a spoke. The last time I broke a spoke in wheels that I'd built was in 1980-something and then it turned out that the spokes themselves were defective in manufacture (as verified by sectioning and microscopic examination). Some of said wheels have done about 80000 miles. However I've broken spokes in nearly every wheelset that I've been stupid enough to use that I didn't build myself.   I think that the difference comes from two main things;

a) I am very careful about the fit of the spokes into the hub and rim and
b) I spend a lot of  time and effort stress-relieving the wheels  (more than some folk spend on the entire build process...)

I think that b) is incredibly important; in recent years I've also taken some 'factory' wheels and subjected them to a more thorough stress-relief and (in other peoples hands) they have also been reliable wheels, at least for 25000 miles or so.

Whether you carry spare spokes and plan to  fit them when you break one is up to you but the problem is best avoided in the first place. I note with interest that in some wheels he rim is more likely to 'take a set' if ridden on when a spoke has broken. This may not prevent you from making the wheel straight again, but the spoke tension is unlikely to be even. However if you replace a spoke immediately, the wheel is more likely to have even tension when trued.

cheers
Title: Re: When a spoke breaks...
Post by: mcshroom on November 17, 2019, 01:43:40 am
I rode 160km of the May as Well Solstice 200 one year on 7 NDS spokes after one unscrewed itself. That was an asymmetric 24 spoke wheel.

On 32 spoke wheels I'd be happy to continue
Title: Re: When a spoke breaks...
Post by: Auntie Helen on November 17, 2019, 07:50:48 am
Probably not helpful but I rode my Velomobile in the summer with 1 front left spoke broken and 2 front right.

I had to be careful with braking and cornering fast, and I could feel the right wheel was out of true, but I was informed by the wheel builder I could continue riding even with another 3-4 broken.

Replacing spokes in a Milan front wheel is not trivial - getting the wheel out takes about an hour.
Title: Re: When a spoke breaks...
Post by: Kim on November 17, 2019, 10:01:20 am
AIUI multitrack means sideways stress on the wheels that bicycles simply don't get, which makes them more prone to such things.  On the other hand, there's less weight on any individual wheel...
Title: Re: When a spoke breaks...
Post by: bludger on November 17, 2019, 10:17:25 am
I had a spoke break on my first audax when I was rolling on cheapo Boardman wheels. I just fettled it so that the brake rub wasn't so bad and continued. The spoke went about 110 into the 200.

Then again I speak as someone who has ridden a bike for several weeks with a busted spoke  ;D I would definitely persevere. Since my newest wheels are straight pull spokes I might source some spares since they are hopefully a doddle to swap out.
Title: Re: When a spoke breaks...
Post by: Andrew Br on November 17, 2019, 05:10:11 pm

 I've found that  provided I'm riding on wheels that I've built myself, I'm extremely unlikely to break a spoke. The last time I broke a spoke in wheels that I'd built was in 1980-something and then it turned out that the spokes themselves were defective in manufacture (as verified by sectioning and microscopic examination). Some of said wheels have done about 80000 miles.


Snip

Given your oft reported aversion to disc brakes, how do you make a rim-braked wheel last 80,000 miles Brucey ?
I've managed to chomp through the rim of (an admittedly factory built wheel) in ~3000 miles.

Do you secretly ride disc or is the decimal point in the wrong place ?

FWIW QG, I also had a spoke break on a 32h disc brake rear wheel on a 200k. I don't know what caused it to break but I carried on and finished with no issues. The rim was fine when I got it sorted.



Title: Re: When a spoke breaks...
Post by: LittleWheelsandBig on November 17, 2019, 05:23:40 pm
I wore out exactly one road rim ever when I lived somewhere reliably warm and dry. Dust isn't too aggressive to rims but gritty mud and salt are killers.

One spoke missing in a 32 hole rim, particularly a deeper section rim, means very little and even less so when you don't have to keep brake pads aligned to the rim. Ride it as far as you need to get to the finish but get concerned if you break a second spoke.

QG, I rode PBP03 with a spoke breaking every 200km on average. This was a bit of a problem since the rear wheel in question only started with 28 spokes. In mitigation, those spokes were galvanised and nearly 40 years old. The rusted spoke threads (and lack of any replacement spokes) meant that retruing my elderly Moulton's 16" Duomatic wheel was not possible. Luckily the coaster brake meant that the progressively more warped rim just imparted a samba rhythm through the saddle and I got to the finish before too many spokes let go.
Title: Re: When a spoke breaks...
Post by: Ian H on November 17, 2019, 06:33:36 pm
I once made a temporary replacement from a longer spoke cut down, an elbow bent at the right length and the free end bent down towards the axle before tensioning. 

It was meant as temporary but it never got replaced, and never gave any trouble.
Title: Re: When a spoke breaks...
Post by: LittleWheelsandBig on November 17, 2019, 06:36:21 pm
The famous Z-bend spoke. Hoshi used to make radically wide aero SS spokes with Z-bends so that the hubs didn't have to be modified/ keyholed.

https://www.wheelfanatyk.com/blog/z-spokes/
Title: Re: When a spoke breaks...
Post by: Paul H on November 17, 2019, 07:15:28 pm
I carry a FiberFix in my toolkit.  I've never had to use that, either, but I saw one save the day when someone on a FNRttC with a low-spoke-count bling wheel hit a pothole of doom, and decided it was a pretty neat idea.
I carried one for some years, then read a review in Cycle.  If Chris Juden couldn't get it to work there didn't seem much chance of me doing so, it languished in the bottom of the spares box till I needed a bit of strong string for something...
 https://www.cyclinguk.org/sites/default/files/document/migrated/publication/201307018-reviews-mio-cyclo-305hc-great-british-bike-rides.pdf

I can see how it'd help on a low spoke count wheel, but that's of no use to me.
Title: Re: When a spoke breaks...
Post by: Patevellian on November 17, 2019, 08:32:09 pm
Lost 2 spokes due to a fractured non drive side flangeabout  half way on a 200k audax. As it happened, I was only about 15k from home at that point  but decided to carry on after removing the mudguard to be collected later. No problems for the duration, but on later inspection several of the eyelets on the drive side (Mavic T261) had developed hairline cracks radiating from them. Not sure if they were already present before hand though.
Title: Re: When a spoke breaks...
Post by: mzjo on November 17, 2019, 09:08:37 pm
No fear to ride on it without replacing the spoke if that was the only option other than DNF - but i would almost certainly want to adjust the other spokes to take as much warp out as possible (unless i was within 30 mins of the finish in which case I would finish before bothering to touch it).
 My rule for what it's worth is if my bum can feel it I want to adjust it and if my bum can't feel it I won't know anything is wrong in the first place (and the only spoke problem I have had in the last 10 years, possibly 20 years, was one that came unscrewed; they were a bit short and the one that unscrewed had the speedo magnet attached to it which might have been the cause). Cat had the same 32 spoke wheel and broke a spoke on a North Oxford pothole. She thought it was wrecked, I took about 1 minute to make it acceptably round (it wasn't very far out, certainly rideable), then replaced the spoke and retrued. I now use it and it has given no further trouble. 
Title: Re: When a spoke breaks...
Post by: Nightmare-1 on November 20, 2019, 12:32:35 am

 I've found that  provided I'm riding on wheels that I've built myself, I'm extremely unlikely to break a spoke. The last time I broke a spoke in wheels that I'd built was in 1980-something and then it turned out that the spokes themselves were defective in manufacture (as verified by sectioning and microscopic examination). Some of said wheels have done about 80000 miles.


Snip

Given your oft reported aversion to disc brakes, how do you make a rim-braked wheel last 80,000 miles Brucey ?
I've managed to chomp through the rim of (an admittedly factory built wheel) in ~3000 miles.

Do you secretly ride disc or is the decimal point in the wrong place ?

FWIW QG, I also had a spoke break on a 32h disc brake rear wheel on a 200k. I don't know what caused it to break but I carried on and finished with no issues. The rim was fine when I got it sorted.

No,
His secret weapon is Sturmey Archer Hub brakes.
Title: Re: When a spoke breaks...
Post by: bludger on November 20, 2019, 12:52:21 am
I have a mate who keeps telling me that hub brakes are going to be the Next Big thing in cycling industry marketing hype.
Title: Re: When a spoke breaks...
Post by: Brucey on November 20, 2019, 01:32:19 am

 I've found that  provided I'm riding on wheels that I've built myself, I'm extremely unlikely to break a spoke. The last time I broke a spoke in wheels that I'd built was in 1980-something and then it turned out that the spokes themselves were defective in manufacture (as verified by sectioning and microscopic examination). Some of said wheels have done about 80000 miles.


Snip

Given your oft reported aversion to disc brakes, how do you make a rim-braked wheel last 80,000 miles Brucey ?
I've managed to chomp through the rim of (an admittedly factory built wheel) in ~3000 miles.

Do you secretly ride disc or is the decimal point in the wrong place ?

I don't think I'm especially  averse to disc brakes per se (I've been using them for decades on some bikes) I just don't think that they free of issues and/or are always best thing for every application.    I think that they come with as many downsides as upsides in many applications; not so much a tasty treat that suits anyone  as just another  'choose your poison' option; no brakes are free of compromise. Folk assume there is a choice between rim brakes (normally on badly machined, swarf-releasing 'soft-as-shite' rims) and disc brakes only.  There are also coaster brakes, roller brakes, band brakes, and expanding drum brakes.  Each has their own virtues and shortcomings. 

By miles, I ride most on rim brakes and drum brakes these days, with discs in third place. By length of time I spend faffing with them, I spend most time on disc brakes and least on drum brakes.

To make a rim brake wheel last that long you have to

a) build it well (*)
b) get lucky (with potholes etc)
c) be careful about the brake blocks you use
d) not use the brakes very much

When out on a typical training ride I mightn't have to use the brakes more than once every ten miles or so, and then I'd normally use the front not the rear brake; the front rim is nearly always cleaner (so less net wear) and the front brake is going to stop you better too. On such a bike the rear brake is only there for emergencies really. Other uses would favour different brakes/bikes and generate other wear rates.

(*)  nothing lasts for ever; two years ago the hub on one of my highest mileage wheels broke an axle and the replacement internal (which I built from spare parts) turned out not to be the same; to my consternation this suffered a catastrophic failure just yesterday, of the 'wheel won't turn any more so you will have to carry the bike' variety.  I honestly though the wheel was scrap but  to my surprise repair was possible, and  not only that an hour or so after starting work, I was rolling again.  The culprit was a change of material specification in one of the parts in the hub; some twit had taken a design that had been manufactured for about thirty years and had been quite reliable, and had decided that they 'knew better' so had downgraded the material used in one of the most highly stressed parts. Duh.

cheers
Title: Re: When a spoke breaks...
Post by: fboab on November 20, 2019, 12:11:30 pm
Broke a spoke about 700km into BOB 1000. the other 27 got my lardy arse round- Belgian roads are sh1te.

Broke several spokes (4? maybe even 5) on posties 300 in 2015. We plodded to the finish with a fibrefix and no rash descents. Also lost spoke(s) on an Upper Thames one year. Lost a couple on a Flatlands and had to get the wheel repaired which destroyed the fun of the ride, but we finished in time.

I can't imagine DNF-ing for a spoke break. On a solo I'd have to work quite hard to pringle the wheel enough for the discs to stop working. On the tandem there's a great deal of built in redundancy with 48 of the beggars, and I've always had a pilot who can sort it, at least long enough to finish.
Title: Re: When a spoke breaks...
Post by: quixoticgeek on November 20, 2019, 04:04:16 pm
if a NDS spoke fails in a modern 10/11s wheel then one or more of the spoke crossings on the drive side comes slightly further to the right and this means there is an increased  risk that the RD will end up in the wheel if you use bottom gear.

 There is a similar risk if the wrong one of a DS spoke pair fails; if an 'inside' spoke from the driveside fails the outside spoke that crosses it is pulled straighter than normal and this again decreases the clearance to the RD in bottom gear.

So if you break a spoke and carry on then I would suggest that you make a point of avoiding use of the largest sprocket.

I have a 40t sprocket for the largest, which means the rear mech is never close to the spokes.

Interestingly, studying the break of the spoke, it's not at the eye, or the bend, but about 30-40mm from the hub. I'm wondering if it got damaged when my rear mech got knocked a couple of months ago when it would accidentally shift into -1 rather than 1st. jamming up, potentially damaging 1 or more spokes. I'm taking the bike to the vet Friday, we'll know more when the wheel is off the bike and we can clearly see both bits of broken spoke.

Quote

FWIW I carry kit to repair a broken spoke (which I have not had to use for decades) when I'm touring but I don't bother the rest of the time. I've found that  provided I'm riding on wheels that I've built myself, I'm extremely unlikely to break a spoke. The last time I broke a spoke in wheels that I'd built was in 1980-something and then it turned out that the spokes themselves were defective in manufacture (as verified by sectioning and microscopic examination). Some of said wheels have done about 80000 miles. However I've broken spokes in nearly every wheelset that I've been stupid enough to use that I didn't build myself.   I think that the difference comes from two main things;

a) I am very careful about the fit of the spokes into the hub and rim and
b) I spend a lot of  time and effort stress-relieving the wheels  (more than some folk spend on the entire build process...)

I think that b) is incredibly important; in recent years I've also taken some 'factory' wheels and subjected them to a more thorough stress-relief and (in other peoples hands) they have also been reliable wheels, at least for 25000 miles or so.

Whether you carry spare spokes and plan to  fit them when you break one is up to you but the problem is best avoided in the first place. I note with interest that in some wheels he rim is more likely to 'take a set' if ridden on when a spoke has broken. This may not prevent you from making the wheel straight again, but the spoke tension is unlikely to be even. However if you replace a spoke immediately, the wheel is more likely to have even tension when trued.

I carry spare spokes, I even carry a lockring tool. But as I don't have the skill to build a wheel, the thought process was always having the materials for a bike shop to fix it if things went tits up on a tour/race.

The rim is an H+son Archetype. Does that have any bearing on the advice?

J
Title: Re: When a spoke breaks...
Post by: mark on November 20, 2019, 05:49:48 pm
I carry spare spokes, I even carry a lockring tool. But as I don't have the skill to build a wheel, the thought process was always having the materials for a bike shop to fix it if things went tits up on a tour/race.

The rim is an H+son Archetype. Does that have any bearing on the advice?

J

Replacing one or two spokes and getting the wheel true enough to keep from fouling the frame or rear derailleur is much easier than building a whole wheel from scratch. With a little care and thought, you could probably use the spokes, lock ring tool and spoke wrench (you do carry one of those?) that you already carry to repair the wheel well enough to finish your tour/race/whatever, and find a bike shop for permanent repairs at your leisure, after your tour/race is over. As Kim mentioned upthread, a FiberFix is a good thing to have in your tool kit. It will let you replace a spoke without removing the cassette or brake disc, and there's no need to worry about having the right size spoke.

https://www.sjscycles.co.uk/spokes/fiber-fix-emergency-replacement-spoke/?geoc=US
Title: Re: When a spoke breaks...
Post by: phil w on November 20, 2019, 06:39:17 pm
On my new recumbent build I've built the spare spokes into the wheel, having gone for 36 spokes front and back. When building the wheel I noticed that truing was much quicker / easier than my last 32 spoke wheel. It may just be that I've got better at building wheels.
Title: Re: When a spoke breaks...
Post by: Kim on November 20, 2019, 07:21:20 pm
On my new recumbent build I've built the spare spokes into the wheel, having gone for 36 spokes front and back. When building the wheel I noticed that truing was much quicker / easier than my last 32 spoke wheel. It may just be that I've got better at building wheels.

If they're different sizes, smaller wheels are much easier to build (down to the point where there isn't much room for the tension gauge / spoke key / any knuckles you'd like not to bruise, where it becomes a bit of a faff).
Title: Re: When a spoke breaks...
Post by: Brucey on November 21, 2019, 12:17:08 am

Interestingly, studying the break of the spoke, it's not at the eye, or the bend, but about 30-40mm from the hub. I'm wondering if it got damaged when my rear mech got knocked a couple of months ago when it would accidentally shift into -1 rather than 1st. jamming up, potentially damaging 1 or more spokes. I'm taking the bike to the vet Friday, we'll know more when the wheel is off the bike and we can clearly see both bits of broken spoke.

that's interesting; failures at mid length are pretty rare. I shall be interested to hear what you conclude.

Quote
I carry spare spokes, I even carry a lockring tool. But as I don't have the skill to build a wheel, the thought process was always having the materials for a bike shop to fix it if things went tits up on a tour/race.

The rim is an H+son Archetype. Does that have any bearing on the advice?

that rim is pretty stiff (considering its weight) and the material is quite strong. I think it would take a 'bad set' rather less easily than a lot of other rims.

If you replace the spoke immediately then you can normally bring the wheel back straight by adjusting the tension in that one spoke alone, so no great skill is required. However if the rim 'takes a set' then things can get  a bit more complicated. Even so you should be able to get the wheel pretty good by just adjusting the tension in that one spoke.

BTW if you have to slacken the spokes opposite the break (to make it straight-ish) and then ride on the wheel, try to be methodical about the slackening of the opposing spokes, e.g. exactly one full turn on the two opposing spokes. This way you know you just need to retighten them by this amount to get back to where you started, as it were.

cheers
Title: Re: When a spoke breaks...
Post by: Cudzoziemiec on November 21, 2019, 09:58:05 am
I have a mate who keeps telling me that hub brakes are going to be the Next Big thing in cycling industry marketing hype.
It will come in with nuclear fusion.
Title: Re: When a spoke breaks...
Post by: Brucey on November 21, 2019, 10:39:30 am
I have a mate who keeps telling me that hub brakes are going to be the Next Big thing in cycling industry marketing hype.
It will come in with nuclear fusion.

so ~25 years away then.

  It has been ~25 years away for at least 50 years now.... ::-)

Title: Re: When a spoke breaks...
Post by: quixoticgeek on November 22, 2019, 03:43:21 pm

Got the bike to the vet, stuck it up on the stand, dropped the wheel out, and pulled the cassette off.

Most out the outer Drive Side spokes have some damage from the chain coming off. We're gonna replace all 18 DS spokes just to be sure. Will upload photos of damage in a bit.

J
Title: Re: When a spoke breaks...
Post by: Kim on November 22, 2019, 03:51:20 pm
Most out the outer Drive Side spokes have some damage from the chain coming off. We're gonna replace all 18 DS spokes just to be sure. Will upload photos of damage in a bit.

That was my approach after the Tesco bag incident.  Of the non-broken spokes, several were visibly damaged, so I replaced the lot.
Title: Re: When a spoke breaks...
Post by: quixoticgeek on November 22, 2019, 07:04:10 pm

This is the broken spoke. The right hand piece is the short bit that got left on the hub, the left hand bit is the bigger length attached to the rim.

(https://pbs.twimg.com/media/EJ_8BPyXkAAh-rr?format=jpg&name=large)

These are 2 other spokes on the same side:

(https://pbs.twimg.com/media/EJ_8E0pWoAIdpn6?format=jpg&name=large)

(https://pbs.twimg.com/media/EJ_8IPoXUAEB8KX?format=jpg&name=large)

Am starting to think that a dorkdisk isn't such a stupid idea...

J
Title: Re: When a spoke breaks...
Post by: phil w on November 22, 2019, 07:09:04 pm
Was about to say looks like they were hit by chain.
Title: Re: When a spoke breaks...
Post by: Brucey on November 22, 2019, 08:08:38 pm
In the past I've always replaced spokes  damaged like that fairly promptly but a few years ago it occurred to me that I hadn't seen any such spokes actually break.  If they were going to break it would presumably be by initiating a fatigue crack which meant two things to me

a) it probably wouldn't happen immediately and
b) there ought to be ways of preventing the fatigue crack initiation

  So on training wheels (where a spoke failure is not going to be critical if it does happen) I've tried another approach.  What I've done is to remove the spoke if necessary and then dress the spoke damage with a swiss file and if necessary straighten/ peen the spoke surface with a hammer (which introduces compressive residual stresses into the spoke surface, not dissimilar to those left by the swaging process that is used during manufacture of DB spokes).

It looks dramatic if you file the round part of a 14G spoke into a 'D' shape but the thickness across the short side of the D needs to be a deal less than 1.25mm before you have reduced the cross section to the 64% which is comparable to that of the centre part of a 14/16G DB spoke .  This means that even quite badly damaged spokes can be fettled if you want to do this. The spokes are then stress-relieved in the normal way.

You might ask 'why do this?' And the reason I suppose is twofold

1) it is an interesting experiment (and of some relevance if you are 'doing field repairs' as it were) and
2) in a workshop the correct spokes are not always readily to hand or even available.

On the latter point the spokes could be any length,  14G PG, 14-15G DB, 14-16G DB, 13-14G SB, 13G PG, 15G PG and could have different butt lengths and/or different elbow lengths, or be in silver or black finishes. There is more than one type of black finish too. 

So far, using this approach 'no breakages' is an encouraging sign but in truth I have not put enough miles on such wheels to really conclude if it  is or isn't a really sound repair or not.

In most wheels such damage is confined to a region below the spoke crossings so only half the DS spokes are likely to be damaged anyway. It is worth noting that using certain types of DB spoke on the DS means that the 16G part of the spoke may be damaged by the chain. For example Sapim DB spokes have very short butts. I have built wheels with Sapim on the NDS and DT (with longer butts) on the DS, figuring that the DT spokes might be slightly stiffer, but they are also less likely to be seriously damaged since a chain will most likely contact/mark the longer 14G section.

Maybe others could say what time/mileage intervals have passed between such damage occurring and a spoke breakage that has initiated at the damaged part of the spoke?

Previous (bitter) experiences with duff wheels tells me that if the wheels/spokes are bad then you can start to get fatigue failures between about 700 and 2000 miles or so. But these were not 'damaged spokes' per se, they may behave differently.

cheers
Title: Re: When a spoke breaks...
Post by: drossall on November 22, 2019, 10:17:58 pm
But it's got me wondering, when a spoke breaks, what is the thought process on to scratch or not? This was on a 32 spoke wheel.
It goes something like this:
"Oh dear, I've broken a spoke.

Good job I've got another 31 in that wheel."

Gets back on and carries on riding.

One spoke from 32 isn't much of a risk. Last time I broke one it was actually the flange that went, but I did another 150 miles before I had chance to retire that wheel for repair. To be fair, that was on 36s, not 32s.
Title: Re: When a spoke breaks...
Post by: Paul H on November 22, 2019, 10:24:23 pm

We're gonna replace all 18 DS spokes just to be sure. 

That's a lot of DS spokes for a 32 spoke wheel ;)
If it is a 36, then the comments about it being OK with one broke are even more so. 
Quote
Am starting to think that a dorkdisk isn't such a stupid idea...
They have to become fashionable at some point, may as well get in early, or so I've been telling myself for the last twenty years.  Though I'm not sure I've seen one for a 40T cassette.
Title: Re: When a spoke breaks...
Post by: zigzag on November 22, 2019, 11:23:28 pm
ideally, chain should not be coming off and spokes should not be breaking. if it's happened it's a lesson for the future.

a fault on a bike can quickly escalate to other undesirable events. many years ago i've put a new chain before a 600k audax and did not check if the cassette was still ok. riding the audax i found it skipping, on one or two cogs. trying to figure out which cogs i was looking down and pressing hard to make them skip. doing so i nearly went into a huge pothole, which i saw at the last moment. swerving to avoid it i went onto a grass verge, which happened to have a perpendicular ditch. off i go over the bars, in the middle of nowhere (aka wales). luckily only minor damages and i could continue and finish the ride - but it could have ended much worse! lesson learned - the bike(s) should be in top condition at all times and touch wood i didn't have any mechanicals on any of my long rides.
Title: Re: When a spoke breaks...
Post by: andrew_s on November 23, 2019, 12:22:19 am
I carry spare spokes, I even carry a lockring tool. But as I don't have the skill to build a wheel, the thought process was always having the materials for a bike shop to fix it if things went tits up on a tour/race.
If you replace the spoke as soon as possible, and haven't had to fiddle with other spokes to avoid rim brake rub, there isn't much to the wheel building side of it - just replace the spoke, lacing it to the same pattern as the others, and tighten it up until the rim is straight (this does assume the rim was straight before the spoke broke).
If you want to be thorough, stress relieve the replacement spoke by forcing the middle of it sideways as far as you can with hands and gloves, then re-check that the rim is straight and tighten or loosen the spoke as required.
Title: Re: When a spoke breaks...
Post by: quixoticgeek on November 23, 2019, 10:38:23 am
ideally, chain should not be coming off and spokes should not be breaking. if it's happened it's a lesson for the future.

The bike fell over during a storm in Germany, landing drive side down, knocking the rear mech. The rear mech hanger got slightly out of alignment. This resulted in it shifting into -1 rather than 1. Thus the chain falling off.

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a fault on a bike can quickly escalate to other undesirable events. many years ago i've put a new chain before a 600k audax and did not check if the cassette was still ok. riding the audax i found it skipping, on one or two cogs. trying to figure out which cogs i was looking down and pressing hard to make them skip. doing so i nearly went into a huge pothole, which i saw at the last moment. swerving to avoid it i went onto a grass verge, which happened to have a perpendicular ditch. off i go over the bars, in the middle of nowhere (aka wales). luckily only minor damages and i could continue and finish the ride - but it could have ended much worse! lesson learned - the bike(s) should be in top condition at all times and touch wood i didn't have any mechanicals on any of my long rides.

The good ole incident pit.

That's a lot of DS spokes for a 32 spoke wheel ;)
If it is a 36, then the comments about it being OK with one broke are even more so. 
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Am starting to think that a dorkdisk isn't such a stupid idea...
They have to become fashionable at some point, may as well get in early, or so I've been telling myself for the last twenty years.  Though I'm not sure I've seen one for a 40T cassette.

Replace all 16, but ordered 18 spokes so I have a couple of spares. I'm awake, honest.

I was going to try googling for them, but then realised I don't actually know the proper name is.

Given the knock the rear mech+hanger took, and my gravely disposition, I do wonder if I should just ignore the lack of fashionability and add one of those rear mech protector thingies to the dork disk. Reliability trumps all.

J
Title: Re: When a spoke breaks...
Post by: Brucey on November 23, 2019, 11:52:18 am
how long was it between the -1 incident and the spoke failure?

cheers
Title: Re: When a spoke breaks...
Post by: quixoticgeek on November 23, 2019, 01:23:18 pm
how long was it between the -1 incident and the spoke failure?

Early August, but about 2500km or so.

J
Title: Re: When a spoke breaks...
Post by: Jakob W on November 23, 2019, 04:24:28 pm
I think 'spoke protector' or 'spoke guard' are the terms of art; whether anyone makes any suitable for a 40T cassette I don't know.

Regarding mech protectors, IIRC they're a mixed blessing at best: they protect from some knocks, but for more serious crashes you're more likely to bend the frame rather than just the mech hanger, and as they stick out more you're more likely to clip them.
Title: Re: When a spoke breaks...
Post by: phil w on November 23, 2019, 05:05:25 pm
This is where the Shimano mtn bike shadow derailleurs may be of benefit . They are designed not to be as proud of the frame as other rear mechs to help protect them.
Title: Re: When a spoke breaks...
Post by: quixoticgeek on November 23, 2019, 05:07:35 pm
This is where the Shimano mtn bike shadow derailleurs may be of benefit . They are designed not to be as proud of the frame as other rear mechs to help protect them.

I'm running a Shimano XT di2 rear mech.

J
Title: Re: When a spoke breaks...
Post by: phil w on November 23, 2019, 05:31:27 pm
This is where the Shimano mtn bike shadow derailleurs may be of benefit . They are designed not to be as proud of the frame as other rear mechs to help protect them.

I'm running a Shimano XT di2 rear mech.

J

With that electronic gubbins they ought to add a spoke distance sensor to stop it shifting into them  ;D
Title: Re: When a spoke breaks...
Post by: Brucey on November 23, 2019, 06:28:44 pm
how long was it between the -1 incident and the spoke failure?

Early August, but about 2500km or so.

J

well that is comparable to the time taken for fatigue cracks to initiate for other reasons.

FWIW if the spoke was also  bent when the damage occurred, this might cause cyclic stresses to be higher than they would be otherwise (you get damaging tensile stresses on the ID of a bend, as it sees cyclic tension). Stress concentration from the damage plus cyclic stresses from the spoke being bent = recipe for fatigue crack initiation.

The 'repair' protocol I have outlined above ought to mitigate both things, but if the damage is in the thinner 16G part of a DB spoke, it is almost certainly a question of 'when' not if you replace the spoke .

cheers
Title: Re: When a spoke breaks...
Post by: Nightmare-1 on December 06, 2019, 11:19:21 am
This is where the Shimano mtn bike shadow derailleurs may be of benefit . They are designed not to be as proud of the frame as other rear mechs to help protect them.

I'm running a Shimano XT di2 rear mech.

J

With that electronic gubbins they ought to add a spoke distance sensor to stop it shifting into them  ;D
That's a good idea. I wonder why they haven't?
P.S.
I know nothing about how di2 works.
My view is that it's just another electrical thing (that I don't need) to go wrong/break whilst out on a ride!
Title: Re: When a spoke breaks...
Post by: FifeingEejit on December 06, 2019, 12:01:05 pm
This is where the Shimano mtn bike shadow derailleurs may be of benefit . They are designed not to be as proud of the frame as other rear mechs to help protect them.

I'm running a Shimano XT di2 rear mech.

J

With that electronic gubbins they ought to add a spoke distance sensor to stop it shifting into them  ;D

That'd have to go into the cage or cassette, adding cost, the Shadow profile is good but not fool proof and the official line is probably "if you think you have a mech hanger don't ride" or as I've noted Shimano regularly put it "the bike may fall over"

All it's really doing is shifting the cage and therefore chain by x mm per click; because the cogs are also x mm apart.
(It actually shifts x+y and then back shifts y)
You can alter the baseline Z by +/- 16 increments.

You could add cage angle, proximity etc. to it, but they're all adjustable depending on cog sizes and b-screw adjustments,
otherwise good mech hanger location is enough to mess up the gear the mech believes it's in on some frames too.

The Limit screws are still mechanical on rear mechs, one of them on front is however electrionic. (I can't remember which)

Title: Re: When a spoke breaks...
Post by: grams on December 06, 2019, 12:25:30 pm
The Limit screws are still mechanical on rear mechs, one of them on front is however electrionic. (I can't remember which)

The front mechs have no H limit screw. The screw labelled "H" is just an adjustment screw that increases the distance between the servo output arm and the mech cage. Since the servo arm only has limited travel that essentially sets how far the mech can move outwards.

The L screw is a normal limit screw.

They can't have limits implemented electronically because as far as I can tell they don't have absolute positioning feedback, only relative from the rotary encoder.
Title: Re: When a spoke breaks...
Post by: FifeingEejit on December 06, 2019, 12:39:23 pm
The Limit screws are still mechanical on rear mechs, one of them on front is however electrionic. (I can't remember which)

The front mechs have no H limit screw. The screw labelled "H" is just an adjustment screw that increases the distance between the servo output arm and the mech cage. Since the servo arm only has limited travel that essentially sets how far the mech can move outwards.

The L screw is a normal limit screw.

They can't have limits implemented electronically because as far as I can tell they don't have absolute positioning feedback, only relative from the rotary encoder.

Just checked, the latest Di2 mechs only have a high limit screw; the lower limit is electronic.