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When servicing my rear hub I discovered that the drive-side spokes have been damaged by the chain. The spokes are rough to the touch (one even had a sharp edge that caught my nitrile glove) and some have a slight inward bend in them as they leave the hub flange.

Although I only just noticed the damage, I actually remember this happening. This wheel has carried me probably 5,000-10,000 km since the chain drop event.

Should I replace these spokes?

enter image description here

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    I agree with mattnz -- You should replace them eventually. You're unlikely to have several fail at once, so there's no urgent need to replace them this week. Mar 21, 2023 at 21:26
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    No need to do it yesterday, considering that you rode thousands of km on these. Do it when you have time.
    – arne
    Mar 23, 2023 at 7:23

7 Answers 7

19

It is likely damaged spokes will fail prematurely due to fatigue at the stress points caused by the damage. When that happens is anyone's guess, and the wheel may fail for other reasons beforehand.

It would be prudent to replace the spokes. The urgency largely depends on your tolerance for a broken spoke and ruined ride. If the bike is used for long distance touring in remote locations, the need is much more than if it is used casual weekend rides.

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Yes. Replace them. I had similar damage, perhaps slightly deeper, when some debris got caught in my rear derailleur and broke it. After 150km one spoke broke, followed by another two before I got home. Luckily with 36 spoke disc wheels it was still rideable because it would have taken all night to walk home.

If one fails, the stress on the others increases risking a cascade of failures.

Replacing all these spokes isn't particularly difficult. The hardest part is getting the right length. Then replace one at a time, bringing the new one up to tension before replacing the next. The wheel will then be nearly true, and you won't have unduly stressed the undamaged dpokes.

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    Fortunately I built the wheels myself and kept a record of the lengths – so that part is easy. The tricky bit will be replacing them without removing the tyres, tubeless sealant, and rim tape :-) Mar 23, 2023 at 7:31
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    The fact you built them yourself also means truing won't be an issue, but this feels like another downside of tubeless, even if hopefully rare
    – Chris H
    Mar 23, 2023 at 8:40
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    So you might want to do it when you have to replace the tyre (or one of the other related items.)
    – Willeke
    Mar 23, 2023 at 17:13
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    @Willeke as they've lasted so long, that's possible here. I wouldn't as mine didn't
    – Chris H
    Mar 23, 2023 at 17:42
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If I'd seen that soon after the chain drop, I'd say replace as many of the most-damaged spokes you can as soon as practical.

However it has lasted for many thousands of kilometres so the damage may be not as bad as it looks.

I see you have a black coating on the silver metal spokes, and that's going to make damage look worse. If the spokes were over-engineered already, it appears to have simply shrugged off that damage.

Will they fail sooner than undamaged spokes? Probably yes.
How long till the most-damaged spoke fails? Absolutely no way to know.

I would suggest getting some replacement spokes at your leisure, and replacing the most-damaged ones. However I'd totally continue to ride the bike as-is until it is convenient.

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    Simply owning spare spokes is likely enough to stop them from ever breaking.
    – Criggie
    Mar 22, 2023 at 2:50
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    the frame where I broke several this way has spare spokes attached to it. They didn't help, with my luck though at the time I couldn't have fitted them without being at home. Now I do carry a roadside cassette removal tool - and I should look into spare spokes for my new light endurance bike
    – Chris H
    Mar 22, 2023 at 10:15
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Really depends on how deep and sharp the scratches are.

Spokes have the highest stress at the J bend and at the nipple. So a straight spoke (same diameter everywhere) actually has unnecessary material in the middle section. More expensive spokes are “double butted” with the middle section thinner than the rest to reduce weight (and maybe increase elasticity).

A spoke like the DT Swiss Revolution with 2mm diameter at the ends and only 1.5mm in the middle (that’s only 56% the cross section area!) isn’t really weaker than a cheaper spoke with 2mm diameter throughout. Granted, they get the diameter reduction through a careful cold forging process and have a very smooth transition from 2mm down to 1.5mm. Not sharp scratches which will act as stress risers. It could actually be helpful to use some sand paper to smooth down the sharp edges.

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  • The dangerous stress risers are at the "valleys" of the gouges. It won't really help much to sand the "peaks" smooth.
    – MaplePanda
    Mar 22, 2023 at 20:30
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    @MaplePanda: True, but if you manage to get in there and smooth out the “valleys” it should help, right? Theoretically you could just keep sanding until it’s completely smooth, then measure how much diameter you have remaining and if it’s more than 1.5mm it’s probably fine.
    – Michael
    Mar 22, 2023 at 20:45
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Agree, from extensive experience, that even badly nicked spokes rarely break apart from at the contact point with the hub, or more commonly the head shears off. However the force to nick the spoke also stressed the bends and the head - they are the high risk spokes now.

So while your cassette is removed, save yourself even one ruined ride by replacing all damaged spokes on the drive train side.

You do carry a spoke spanner with you on every single ride I hope. That's of more practical use than a puncture repair kit : Pump, two tubes, two tyre levers, spoke spanner, allen keys - the roadie's survival kit.

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    Welcome to the site - excellent first answer.
    – Criggie
    Mar 22, 2023 at 20:43
  • 1
    Thanks - appreciated. I'm still not able to authenticate my account for some reason, go through all the steps to validate my email address and it just traps me in an infinite loop as below, So let's see what happens ~~~~~ Forgot your account’s password? Enter your email address and we’ll send you a recovery link. <--> Could not complete signup - email address was not verified.
    – Nick Myra
    Mar 23, 2023 at 13:31
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Anecdotally, I've ridden plenty with spokes that looked like those, never had a break at that location, always at the nipple or right at the elbow, and more often on the non-drive side. Having said that, spokes don't cost that much, and since you already have the wheel out and the cassette off, it would be pretty easy to replace them now. I'd replace ones that are gouged and/or bent. Any with just minor scratches I'd leave

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  • Spokes are cheap. Paying a bike store to build the wheel properly is not necessarily cheap (although you should ask). For newer riders, I would recommend not learning to build the wheel yourself.
    – Weiwen Ng
    Mar 22, 2023 at 15:51
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Given the tradeoffs and the location of the damage, I'd agree with the suggestion to replace the spokes preemptively. However, I offer some further information below. This verges on overthinking the issue, however.

The engineering term for the phenomenon that mattnz referred to is that the gouges likely create stress risers or stress concentrators. As you keep riding, those spokes cycle through loaded and unloaded phases. Those stresses will get concentrated at the gouges. The drive-side spokes are also under more tension, and if they break, they will distort the wheel more than if a non-drive spoke breaks.

If you don't replace the spokes, you could exercise watchful waiting, a term normally used in medicine where you don't actively treat a disease (including a suspected disease), but you periodically monitor its progress. You'd be looking for any worsening, e.g. cracks forming. A potential problem with this approach is that failures may occur suddenly rather than gradually. We normally associate metal, especially steel, with gradual rather than sudden failures, and carbon with the latter. However, those are really thin steel structures, and we might not be able to see warning signs before a failure propagates.

If we think of a dent in a frame, we would generally advise people to use watchful waiting, although it would depend on how thin the frame tubing was (ultralight frame = no safety margin) and where the dent was (in a highly stressed location like towards the ends of the downtube = more likely to fracture, close to head tube = immediate uncontrolled crash if it fails). Here, others have observed that if spokes break, that will end the ride immediately, and probably stress the rim beyond repair. It has to be said that it shouldn't crash you, at least - the front wheel would crash you.

Another thing you could do would be to ask the opinion of an experienced wheelbuilder. They could have some experience as to how likely this would be to fail. Naturally, this also won't be a perfect source of information, because they will have competing commercial interests.

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