Spokes snapping at elbow

jds_1981

Okay,

Not that unusual, my rear drive side spokes are now snapping quite regularly and one none drive side has gone. Time to rebuild.
I noticed after unscrewing the second spoke (first one popped as i started unscrewing it) that the inside of the elbow was actually slightly worn.
These wheels have been kept under reasonable maintenance although the ride in is quite rough and wet or dusty. Normal wear then?
As an aside, the rims are cheap mach1 820. Can't find a recommended tension for the spokes so what is a good rule of thumb?

rhodrich

Generally, spokes, when they do snap, more often than not snap at the elbow, which is the area of highest stress.

Once more than one or two go, you're right to say that the wheel should be replaced/rebuilt.

If the spokes start snapping before the rim is worn out, this usually points to either poor quality spokes, or a poorly built wheel, with tension that is too low or uneven. Spokes shouldn't wear on the elbow, as they should always be in tension. It's when the tension is so low that they go out of tension as the wheel is loaded when you get big problems. It's rarely a problem with the rim.

If you decide to rebuild the wheel from scratch, I'd recommend reading 'The bicycle wheel' by Jobst Brandt, which should tell you all you need to about how to build a strong, reliable wheel.

jds_1981

Well, they aren't great quality wheels but I have kept them reasonably tensioned. They have however done about 10k miles on canal track, ridden fairly hard.

As they're disc brakes I suspect it is fairly natural for the spokes to go before wear on the rim

The few I've looked at all seem to have a similar amount of wear so I don't think it is due to a few being under tightened.

UndercoverElephant

Was it drive side or non that was worn like that? If drive side, it could be that your limit screws were off and the chain got trapped between cassette and spokes - that's a pretty quick way to kill spokes.

jds_1981

UndercoverElephant wrote:

Was it drive side or non that was worn like that? If drive side, it could be that your limit screws were off and the chain got trapped between cassette and spokes - that's a pretty quick way to kill spokes.

Both, it's on the inside of the elbow only. Will see if I can take some pictures of a few.

rhodrich

10k miles is nothing for a well built wheel. Once built, they shouldn't need touching. The fact that you've had to 'keep them reasonably tensioned' suggests to me that they were badly built to start with. If they've gone out of tension through normal riding, there is wear on the elbows, and spokes are snapping, the tension must have been too low to start with. Not uncommon with cheap machine built wheels.

UndercoverElephant

jds_1981 wrote:

UndercoverElephant wrote:

Was it drive side or non that was worn like that? If drive side, it could be that your limit screws were off and the chain got trapped between cassette and spokes - that's a pretty quick way to kill spokes.

Both, it's on the inside of the elbow only. Will see if I can take some pictures of a few.

In which case I suspect they were cheap, crappy spokes and probably weren't quite tight enough either.

itboffin

damn you and your spoke thread, my commuter started making a horrible noise yesterday, i've worked out its the rear wheel but nothing looks visually wrong, one spoke has more movement and sounds dead

if its loose then wouldnt the wheel be out of true, shimano RS10 so low spoke count

jds_1981

Wheel was cheap but reasonably tensioned.

Heh, my first indication of trouble was the free week became very sticky. After the ride realised a spoke was poking into the cassette, but would spring free after it bent so far