spokes breaking... help!!!

ed said:

Alright, backstory: I am a heavy guy who also carries around heavy
stuff in his bag (for example, my heavy bike chain). I've got a bunch
of different fixies, and I've had 2 spokes break in the last week (on
two totally different sets of wheels). Is this a coincidence? I
doubt it. Is there something that I can do? I am looking for any
explanation or rational solutions. (Losing more weight already on the
top of the to-do list.)

1) Front spoke popped while going (slowly) downhill. 700x25 tires
(pumped to about 100psi), heavy looking spokes (though, I am not sure
of the size spec), with a ultegra low-flange hub and Mavic Open Pro
rim. I'd say the wheels are about 6 years old, but were pretty true,
and in good shape (they weren't originally mine). I know the spoke
was under high tension to start, but I didn't believe it was
unreasonably so. It may have been close, however.

2) Rear spoke popped on a older rear wheel... 700x23 tires pumped to
around 100psi again, moderate looking spokes on a stock bianchi pista
wheel (Mavic Cxp 21 rims, stock bianchi spokes and hubs). Not sure
how old the wheels were, again, they weren't originally mine. They
were true, and under average tension to start. Once broken, the wheel
was only slightly out of true.

In both cases the spoke broke right at the bend (of course). If
there's anyone who can give suggestions, or if I can provide more
info, let me know! Now I'm down to the 4th bike...

unless you keep your bikes in the basement next to the swimming pool
chlorine, it's pure coincidence. just like having two flats in the same
week. repair and forget about it.

ed said:

Alright, backstory: I am a heavy guy who also carries around heavy
stuff in his bag (for example, my heavy bike chain). I've got a bunch
of different fixies, and I've had 2 spokes break in the last week (on
two totally different sets of wheels). Is this a coincidence? I
doubt it. Is there something that I can do? I am looking for any
explanation or rational solutions. (Losing more weight already on the
top of the to-do list.)

1) Front spoke popped while going (slowly) downhill. 700x25 tires
(pumped to about 100psi), heavy looking spokes (though, I am not sure
of the size spec), with a ultegra low-flange hub and Mavic Open Pro
rim. I'd say the wheels are about 6 years old, but were pretty true,
and in good shape (they weren't originally mine). I know the spoke
was under high tension to start, but I didn't believe it was
unreasonably so. It may have been close, however.

2) Rear spoke popped on a older rear wheel... 700x23 tires pumped to
around 100psi again, moderate looking spokes on a stock bianchi pista
wheel (Mavic Cxp 21 rims, stock bianchi spokes and hubs). Not sure
how old the wheels were, again, they weren't originally mine. They
were true, and under average tension to start. Once broken, the wheel
was only slightly out of true.

In both cases the spoke broke right at the bend (of course). If
there's anyone who can give suggestions, or if I can provide more
info, let me know! Now I'm down to the 4th bike...

Most threads on the subject on this forum quickly become not worth
reading or getting involved in, ime. However, the "Jobst" method/
theory of stress relieving spokes when the wheel is built has been
very effective for me. I'm also a big guy. I put a pretty good amount
of miles on a pretty small number of wheels, all that I've built, and
don't ever break spokes by fatigue. Also, both thicker-than-normal or
straight gauge 2mm spokes are bad for basically all conventional on-
road purposes for riders of any weight. They distribute loads less
effectively and the extra tensile strength is irrelevant.

Nate Knutson said:

ed said:

Alright, backstory: I am a heavy guy who also carries around heavy
stuff in his bag (for example, my heavy bike chain). I've got a bunch
of different fixies, and I've had 2 spokes break in the last week (on
two totally different sets of wheels). Is this a coincidence? I
doubt it. Is there something that I can do? I am looking for any
explanation or rational solutions. (Losing more weight already on the
top of the to-do list.)

1) Front spoke popped while going (slowly) downhill. 700x25 tires
(pumped to about 100psi), heavy looking spokes (though, I am not sure
of the size spec), with a ultegra low-flange hub and Mavic Open Pro
rim. I'd say the wheels are about 6 years old, but were pretty true,
and in good shape (they weren't originally mine). I know the spoke
was under high tension to start, but I didn't believe it was
unreasonably so. It may have been close, however.

2) Rear spoke popped on a older rear wheel... 700x23 tires pumped to
around 100psi again, moderate looking spokes on a stock bianchi pista
wheel (Mavic Cxp 21 rims, stock bianchi spokes and hubs). Not sure
how old the wheels were, again, they weren't originally mine. They
were true, and under average tension to start. Once broken, the wheel
was only slightly out of true.

In both cases the spoke broke right at the bend (of course). If
there's anyone who can give suggestions, or if I can provide more
info, let me know! Now I'm down to the 4th bike...

Most threads on the subject on this forum quickly become not worth
reading or getting involved in, ime. However, the "Jobst" method/
theory of stress relieving spokes when the wheel is built has been
very effective for me. I'm also a big guy. I put a pretty good amount
of miles on a pretty small number of wheels, all that I've built, and
don't ever break spokes by fatigue. Also, both thicker-than-normal or
straight gauge 2mm spokes are bad for basically all conventional on-
road purposes for riders of any weight. They distribute loads less
effectively and the extra tensile strength is irrelevant.

extra stiffness of thicker spokes can be useful though - more lateral
stiffness can help with shimmy.

urlhttp://www.jimbeam.com/beam/default.aspx?/url said:

extra stiffness of thicker spokes can be useful though - more
lateral stiffness can help with shimmy.

Shimmy is a characteristic of the bicycle frame, having little to do
with spoke thickness or number as testing has shown both by Damon
Rinard (at Trek) and here. Don't throw out old wive's tales as advice
here. How about a reference that supports your contention?

Jobst Brandt

ed said:

Alright, backstory: I am a heavy guy who also carries around heavy
stuff in his bag (for example, my heavy bike chain). I've got a bunch
of different fixies, and I've had 2 spokes break in the last week (on
two totally different sets of wheels). Is this a coincidence? I
doubt it. Is there something that I can do? I am looking for any
explanation or rational solutions. (Losing more weight already on the
top of the to-do list.)

1) Front spoke popped while going (slowly) downhill. 700x25 tires
(pumped to about 100psi), heavy looking spokes (though, I am not sure
of the size spec), with a ultegra low-flange hub and Mavic Open Pro
rim. I'd say the wheels are about 6 years old, but were pretty true,
and in good shape (they weren't originally mine). I know the spoke
was under high tension to start, but I didn't believe it was
unreasonably so. It may have been close, however.

2) Rear spoke popped on a older rear wheel... 700x23 tires pumped to
around 100psi again, moderate looking spokes on a stock bianchi pista
wheel (Mavic Cxp 21 rims, stock bianchi spokes and hubs). Not sure
how old the wheels were, again, they weren't originally mine. They
were true, and under average tension to start. Once broken, the wheel
was only slightly out of true.

In both cases the spoke broke right at the bend (of course). If
there's anyone who can give suggestions, or if I can provide more
info, let me know! Now I'm down to the 4th bike...

Stress relieve your spokes. See Sheldon Brown's site for details.

ed said:

Alright, backstory: I am a heavy guy who also carries around heavy
stuff in his bag (for example, my heavy bike chain). I've got a bunch
of different fixies, and I've had 2 spokes break in the last week (on
two totally different sets of wheels). Is this a coincidence? I
doubt it. Is there something that I can do? I am looking for any
explanation or rational solutions. (Losing more weight already on the
top of the to-do list.)

1) Front spoke popped while going (slowly) downhill. 700x25 tires
(pumped to about 100psi), heavy looking spokes (though, I am not sure
of the size spec), with a ultegra low-flange hub and Mavic Open Pro
rim. I'd say the wheels are about 6 years old, but were pretty true,
and in good shape (they weren't originally mine). I know the spoke
was under high tension to start, but I didn't believe it was
unreasonably so. It may have been close, however.

2) Rear spoke popped on a older rear wheel... 700x23 tires pumped to
around 100psi again, moderate looking spokes on a stock bianchi pista
wheel (Mavic Cxp 21 rims, stock bianchi spokes and hubs). Not sure
how old the wheels were, again, they weren't originally mine. They
were true, and under average tension to start. Once broken, the wheel
was only slightly out of true.

In both cases the spoke broke right at the bend (of course). If
there's anyone who can give suggestions, or if I can provide more
info, let me know! Now I'm down to the 4th bike...

Often, on older wheels, spokes breaking is a sign of a sick
wheel(rim). When the rim gets deformed thru use(dented), the tension
at that spot is low, and the resulting forces are like bending a coat
hanger back-forth-back-forth..break spoke. Rebuild with a new rim is
the answer.

Quoted message said:

urlhttp://www.jimbeam.com/beam/default.aspx?/url said:

extra stiffness of thicker spokes can be useful though - more
lateral stiffness can help with shimmy.

Shimmy is a characteristic of the bicycle frame, having little to do
with spoke thickness or number as testing has shown both by Damon
Rinard (at Trek) and here. Don't throw out old wive's tales as advice
here. How about a reference that supports your contention?

Jobst Brandt

we've discussed this several times before. don't you remember? two
otherwise identical rear wheels, except one has 2.0mm straight gauge
spokes on the drive side. the skinny spoke wheel shimmies easily, the
fat spoke one much less so. it can be induced, but at a higher
frequency - which is what you'd expect from a stiffer spring. damon
rinard's published lateral stiffness data confirms that thicker spokes
make laterally stiffer wheels.

you're right in that shimmy is primarily a function of frame - we've
discussed that before too - but when the resonance of the wheels /and/
frame have coincident frequencies, that's when you have big problems.
thicker spokes shift the frequency of the wheel component a little,
hopefully enough to shift away from that of the frame to be useful.
it's got nothing to do with your gyroscopes.

In article
<[email hidden]>
,

ed said:

Alright, backstory: I am a heavy guy who also carries around heavy
stuff in his bag (for example, my heavy bike chain). I've got a bunch
of different fixies, and I've had 2 spokes break in the last week (on
two totally different sets of wheels). Is this a coincidence? I
doubt it. Is there something that I can do? I am looking for any
explanation or rational solutions. (Losing more weight already on the
top of the to-do list.)

1) Front spoke popped while going (slowly) downhill. 700x25 tires
(pumped to about 100psi), heavy looking spokes (though, I am not sure
of the size spec), with a ultegra low-flange hub and Mavic Open Pro
rim. I'd say the wheels are about 6 years old, but were pretty true,
and in good shape (they weren't originally mine). I know the spoke
was under high tension to start, but I didn't believe it was
unreasonably so. It may have been close, however.

2) Rear spoke popped on a older rear wheel... 700x23 tires pumped to
around 100psi again, moderate looking spokes on a stock bianchi pista
wheel (Mavic Cxp 21 rims, stock bianchi spokes and hubs). Not sure
how old the wheels were, again, they weren't originally mine. They
were true, and under average tension to start. Once broken, the wheel
was only slightly out of true.

In both cases the spoke broke right at the bend (of course). If
there's anyone who can give suggestions, or if I can provide more
info, let me know! Now I'm down to the 4th bike...

Almost certainly the spokes broke from residual
stress in the spoke elbows, residual stress from the
original forming. The rs added to the cyclic strain
cycle in the elbow as the spoke passes the contact
patch and undergoes a momentary tension decrease can
lead to fatigue and fracture the same way repeatedly
flexing a steel wire leads to fracture.

Solution is balanced spoke tension and stress relief
of all spokes.

--
Michael Press

Michael Press said:

In article
<[email hidden]>
,

ed said:

Alright, backstory: I am a heavy guy who also carries around heavy
stuff in his bag (for example, my heavy bike chain). I've got a bunch
of different fixies, and I've had 2 spokes break in the last week (on
two totally different sets of wheels). Is this a coincidence? I
doubt it. Is there something that I can do? I am looking for any
explanation or rational solutions. (Losing more weight already on the
top of the to-do list.)

1) Front spoke popped while going (slowly) downhill. 700x25 tires
(pumped to about 100psi), heavy looking spokes (though, I am not sure
of the size spec), with a ultegra low-flange hub and Mavic Open Pro
rim. I'd say the wheels are about 6 years old, but were pretty true,
and in good shape (they weren't originally mine). I know the spoke
was under high tension to start, but I didn't believe it was
unreasonably so. It may have been close, however.

2) Rear spoke popped on a older rear wheel... 700x23 tires pumped to
around 100psi again, moderate looking spokes on a stock bianchi pista
wheel (Mavic Cxp 21 rims, stock bianchi spokes and hubs). Not sure
how old the wheels were, again, they weren't originally mine. They
were true, and under average tension to start. Once broken, the wheel
was only slightly out of true.

In both cases the spoke broke right at the bend (of course). If
there's anyone who can give suggestions, or if I can provide more
info, let me know! Now I'm down to the 4th bike...

Almost certainly the spokes broke from residual
stress in the spoke elbows,

not "almost certainly" at all - the fatigue crack initiation point is
never a point at which the residual stress profile is high. you can't
connect the dots if they're not on the same page.

bottom line, you're propagating someone else's myth and lore. please
don't. want to offer effective advice on preventing spoke fatigue?
recommend the use of high quality spokes that are made from fatigue
resistant materials and which have been produced with attention to
surface finish detail. better yet, endorse the use of straight pull
spokes instead since the bending motion of the spoke elbow is the real
reason they fatigue and break.

Quoted message said:

residual stress from the
original forming. The rs added to the cyclic strain
cycle in the elbow as the spoke passes the contact
patch and undergoes a momentary tension decrease can
lead to fatigue and fracture the same way repeatedly
flexing a steel wire leads to fracture.

Solution is balanced spoke tension and stress relief
of all spokes.