Spoke broken by chain - autopsy and plan of action

[tatanab]

Dork disc? Is that the plastic disc that sits between cog and spoke?

Goes along with Rooky Rash - the marks on the calf where a novice rider contacts the chainring.

[MikeF]

For the OP dork disc is a plastic spoke protector. Easy to fit with cassette removed.

But I'm still confused by Unisex wheels

[doffcocker]

Lot of developments on this one.

After a few rides with a broken spoke, a second one (also hub side) also caved in. In the end I was able to use spokes from my old wheel as replacements and managed to true the wheel into nice working order.

Unfortunately though within a couple of rides after that, another hub side spoke breaks on me. But to my surprise it wasn't one of the replacement ones from the old wheel, it was one that came with the wheel. And then another.

So in total I have replaced 4 spokes, and now after a few trouble free rides, a 5th has broken, again from the hub side.

Is this just bad luck, poor wheel quality, or is there something wrong with the wheel or something wrong with how I have set about repairing it?

Also, one thing I notice is that my non-hub side spokes are all considerably looser than the hub side? Is this normal?

[Mike Sales]

Also, one thing I notice is that my non-hub side spokes are all considerably looser than the hub side? Is this normal?

Completely normal. This is to produce "dish". The rim is closer to the right flange in order to give room for the cassette and keep the rim central between the frame stays.
It sounds to me as if the whole wheel may have been undertensioned and poorly destressed to begin with though, so that the loads were not well spread and spokes failed early.
Since the rim and hub are new I suggest a rebuild with new spokes by a competent wheel builder.

[pwa]

If you break a spoke and continue riding, that can damage the other spokes and you end up with a succession of broken spokes. It is likely that all the drive side spokes that were on the wheel when the first one went are now living on borrowed time. The only sure way to fix it is to replace all the spokes on the drive side, since every one of them is suspect.

[doffcocker]

Thanks for your replies.

I know it sounds really lazy, is there any shortcut to determining the measurements of the spokes I need to order that doesn't involve taking the wheel and cassette off and removing a full and well spoke to be measured with a spoke ruler?

I could use another spoke from the old wheel again to measure, I suppose but I'd rather know the exact measurement of the current wheel's original spokes, because although the ones from the old wheel fit in the new wheel, I did also have to use the nipples from the old wheel in order for them to reach the rim.

[531colin]

More information needed......in a month or so you have broken 5 spokes in a Shimano wheel......that sounds exceptionally unusual.
Are you absolutely sure its a genuine Shimano?

The first spoke you say broke due to a chain jam between cassette and spokes
.......this spoke should have been scored up by the chain..... was it?
Subsequent spokes ....scored up by the chain?
Or a clean break where the spoke bends at the hub flange? Or something else?

Most driveside spokes fail due to fatigue at the bend. There are 3 phases to fatigue failures; crack initiation, propagation, and failure itself.
Of these, crack initiation is the longest phase, so this suggests (in the absence of exact description of the broken spokes requested above) that all your failures started initiation at about the same time, ie. as soon as you started riding the wheel, and the spokes have lasted a month or so.