spokes always breaking

Dean Edwards said:

I keep getting broken spokes on the rear wheel and only on the cluster side of the hub. I have
trued the wheel after replacing broken spokes and there never seem to be any over taught spokes.
The bike is a rockhopper with mavic x139 rims and specialised hubs.

How can I sort this out or is it worth buying a new wheel?

Its either too loose spokes or not stress relieved spokes. You will break the rim or hub flange
before you break the spoke through too much tension.

Tim.

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Tim Woodall <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

Dean Edwards said:

I keep getting broken spokes on the rear wheel and only on the cluster side of the hub. I have
trued the wheel after replacing broken spokes and there never seem to be any over taught spokes.
The bike is a rockhopper with mavic x139 rims and specialised hubs.

How can I sort this out or is it worth buying a new wheel?

Its either too loose spokes or not stress relieved spokes. You will break the rim or hub flange
before you break the spoke through too much tension.

50% correct - too loose spokes have nothing to do with it. (Of course, it's good to have high spoke
tension, but that's to ensure that the wheel does not collapse.)

Lack of stress relieving is the cause. So now that the OP has a wheel full of fatigued spokes, he
has these options:

a. replace any broken spokes, true and retension the wheel (to a decent high spoke tension). Use
Jobst's stress-relieving technique to make all the spokes less susceptible to fatigue failure,
and to indicate when the tension is high enough.

OR

b. detension the wheel (gradually!), remove and discard all existing spokes. Rebuild existing hub
and rim with brand new spokes, correctly tension and stress relieve as in (a).

OR

c. buy new wheel, but ensure that it is correctly tensioned and stress relieved as in (a).

David Green Cambridge

Dean Edwards said:

I keep getting broken spokes.........

I had the same problem with a pair of wheels, I was forever replacing spokes, in fact I used to ride
with two spares taped to my pump just in case. In the end I took them into my LBS and had them
rebuilt. They were never a problem after that.

"David Green" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Tim Woodall <[email hidden]> wrote in message

news:<[email hidden]>...

Quoted message said:

Quoted message said:

Dean Edwards said:

I keep getting broken spokes on the rear wheel and only on the cluster

side

Quoted message said:

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of the hub. I have trued the wheel after replacing broken spokes and

there

Quoted message said:

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never seem to be any over taught spokes. The bike is a rockhopper

with

Quoted message said:

Quoted message said:

Quoted message said:

mavic x139 rims and specialised hubs.

How can I sort this out or is it worth buying a new wheel?

Its either too loose spokes or not stress relieved spokes. You will

break

Quoted message said:

Quoted message said:

the rim or hub flange before you break the spoke through too much

tension.

Quoted message said:

50% correct - too loose spokes have nothing to do with it. (Of course, it's good to have high
spoke tension, but that's to ensure that the wheel does not collapse.)

Apart from that spokes do break before the rims or hub due to over tightening. Maybe if you use
extra strong ones they don't but mine certainly
do.

Quoted message said:

Lack of stress relieving is the cause. So now that the OP has a wheel full of fatigued spokes, he
has these options:

How can you be sure? Are you saying having loose spokes doesn't increase fatigue?

"Frank X" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

"David Green" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Quoted message said:

50% correct - too loose spokes have nothing to do with it. (Of course, it's good to have high
spoke tension, but that's to ensure that the wheel does not collapse.)

Apart from that spokes do break before the rims or hub due to over tightening. Maybe if you use
extra strong ones they don't but mine certainly
do.

Er? Do you mean that you break spokes during tensioning, or, when your spokes break you feel it's
due to them being over tight?

Have you read 'the Bicycle Wheel' by the way?

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Lack of stress relieving is the cause. So now that the OP has a wheel full of fatigued spokes,
he has these options:

Quoted message said:

How can you be sure?

Because how else do spokes fail? Even in a tightly spokes wheel, spokes are only at a fraction of
the tension required to break them.

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Are you saying having loose spokes doesn't increase fatigue?

Yes. In any case, the point is that some places in the metal will be close to their yield point
unless you stress relieve them. It's that proximity to their YP that makes these areas prone to
fatigue, not the tension in the spoke overall.

DG

"David Green" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Frank X" <[email hidden]> wrote in message

news:<[email hidden]>...

Quoted message said:

Quoted message said:

"David Green" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Quoted message said:

50% correct - too loose spokes have nothing to do with it. (Of course, it's good to have high
spoke tension, but that's to ensure that the wheel does not collapse.)

Apart from that spokes do break before the rims or hub due to over tightening. Maybe if you use
extra strong ones they don't but mine

certainly

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do.

Er? Do you mean that you break spokes during tensioning, or, when your spokes break you feel it's
due to them being over tight?

I've broken them through overtightening. You twist the spoke key on brand new spokes they break not
the rim or hub. Double butted, which I use, break at the either of the two points where the spoke
goes from thick to thin.

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Have you read 'the Bicycle Wheel' by the way?

No, but I'm smart enough to reaslise there is a flaw in my technique ;o)

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Lack of stress relieving is the cause. So now that the OP has a wheel full of fatigued spokes,
he has these options:

Quoted message said:

How can you be sure?

Because how else do spokes fail? Even in a tightly spokes wheel, spokes are only at a fraction of
the tension required to break them.

Spokes break becuase of fatigue if spokes are too loose the stresses on the spoke change more as the
wheel rotates hence more fatigue.

Quoted message said:

Quoted message said:

Are you saying having loose spokes doesn't increase fatigue?

Yes. In any case, the point is that some places in the metal will be close to their yield point
unless you stress relieve them. It's that proximity to their YP that makes these areas prone to
fatigue, not the tension in the spoke overall.

I'm not saying stress relief isn't a good idea, but I think you are wrong, undertensioned spokes do
suffer from increased fatigue.

David Green said:

Quoted message said:

Its either too loose spokes or not stress relieved spokes. You will break the rim or hub flange
before you break the spoke through too much tension.

50% correct - too loose spokes have nothing to do with it. (Of course, it's good to have high spoke
tension, but that's to ensure that the wheel does not collapse.)

I've noticed that the spokes that are breaking are of one particular orientation: It's alternate
spokes on the driveside, the ones where the nipples are on the external, cluster-side face of
the flange.

None of my replacement spokes have bust yet so hopefully I'm doing something right.

"Frank X" <[email hidden]> wrote in message
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I've broken them through overtightening. You twist the spoke key on brand new spokes they break
not the rim or hub. Double butted, which I use, break at the either of the two points where the
spoke goes from thick to thin.

That sounds like lack of lubrication on the spoke threads is causing you to twist the spoke when you
tighten the nipple. Certainly, I've had that happen, on old wheels with 'frozen' nipples. But that's
not 'overtensioning', it's twisting.

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Have you read 'the Bicycle Wheel' by the way?

No, but I'm smart enough to reaslise there is a flaw in my technique ;o)

I think you'd get a lot out of reading it. Ideal birthday present to yourself!

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Because how else do spokes fail? Even in a tightly spokes wheel, spokes are only at a fraction
of the tension required to break them.

Spokes break becuase of fatigue if spokes are too loose the stresses on the spoke change more as
the wheel rotates hence more fatigue.

No. The tension in each spoke reduces by a fixed amount each time it is vertically underneath the
hub. (This depends only on your weight.) Unless a spoke is completely slack, it doesn't matter what
tension it is - it still experiences the same fluctuation in its tension.

Quoted message said:

Quoted message said:

Quoted message said:

Are you saying having loose spokes doesn't increase fatigue?

Yes. In any case, the point is that some places in the metal will be close to their yield point
unless you stress relieve them. It's that proximity to their YP that makes these areas prone to
fatigue, not the tension in the spoke overall.

I'm not saying stress relief isn't a good idea, but I think you are wrong, undertensioned spokes
do suffer from increased fatigue.

If you can find anywhere in 'the Bicycle Wheel' where this is explained, please let me know.

David.