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Lifetime of spokes?



 
 
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  #1  
Old July 31st 03, 02:43 AM
FlashSteve
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Default Lifetime of spokes?

Bull****! I have wheels that are 8 or 9 years old, 30,000+ miles (much of it
in the rain) and I have never broken a spoke. I ride only hand-built,
pre-stressed and re-tensioned wheels with DT, Sapim, or Wheelsmith spokes. I
am 170 lbs, ride on O.K. roads.

So, I am no expert in wheel-building (there are MANY discussions in this group
on that subject), but the shop girl is feeding you an uninformed line of BS.

Steve Scarich
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  #2  
Old July 31st 03, 03:52 AM
Chris Neary
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Default Lifetime of spokes?

Her thought was
that the stainless steel the spokes are made of is starting to "crystalize"
and become brittle with age. This makes it prone to breaking.


This is a classic "old wive's tale" told by uneducated welders, etc.

The solid state of steels, stainless or otherwise, is a crystal. Your spoke
did not further "crystalize" in use.

She did not
think the problem was caused by looseness of some spokes.


Why not? If the quality of the wheel build was such that one spoke failed,
it is not out of the question that other spokes are experiencing similar
fatigue loadings and damage.

Suggested fix was
to re-spoke the wheel (~$50) or buy a new wheel (~$70) or just fix the
spokes as they break (~$10 labor total plus 66 cents for each spoke). For
now, I'm doing the last.


I vote for biting the bullet and having the wheel respoked or buying a new
wheel. Life's too short to be running back to the shop every time a spoke
pops, and at this point you've almost spent half the cash required to
re-spoke the wheel. I would try to find out who in the area has the best
reputation as a wheelbuilder, though - a professions go, wheelbuilding is as
much art as science.


Chris Neary


"Science, freedom, beauty, adventu what more could
you ask of life? Bicycling combined all the elements I
loved" - Adapted from a quotation by Charles Lindbergh
  #4  
Old August 1st 03, 03:42 PM
Terry Morse
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Default Lifetime of spokes?

Peter Cole wrote:

Spokes never break in the center. 90% of the time they break at the elbow, the
rest at the threads, that's where the residual manufacturing/building stresses
are.


Never say never. I've seen a spoke break in the middle before, and
it makes a pretty spectacular noise. The culprit was corrosion,
probably started at a surface scratch.
--
terry morse Palo Alto, CA http://www.terrymorse.com/bike/
  #5  
Old August 1st 03, 04:31 PM
[email protected]
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Default Lifetime of spokes?

Terry Morse writes:

Spokes never break in the center. 90% of the time they break at the
elbow, the rest at the threads, that's where the residual
manufacturing/building stresses are.


Never say never. I've seen a spoke break in the middle before, and
it makes a pretty spectacular noise. The culprit was corrosion,
probably started at a surface scratch.


As I said, most of my spoke failures are from nicks made by the chain
falling into the spokes (because the end stops of today's derailleurs
are too short to prevent going past the lowest sprocket on my 6-speed
FW's) where the exception was a failure in the middle that showed no
indication for its failure showing no crack propagation, only a
sloping complete separation. When it went, it sounded no different
from any other spoke failure, like a small hammer blow on the hub.

Jobst Brandt

Palo Alto CA
  #6  
Old August 1st 03, 04:35 PM
[email protected]
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Default Lifetime of spokes?

Terry Morse writes:

Spokes never break in the center. 90% of the time they break at the
elbow, the rest at the threads, that's where the residual
manufacturing/building stresses are.


Never say never. I've seen a spoke break in the middle before, and
it makes a pretty spectacular noise. The culprit was corrosion,
probably started at a surface scratch.


As I said, most of my spoke failures are from nicks made by the chain
falling into the spokes (because the end stops of today's derailleurs
are too short to prevent going past the lowest sprocket on my 6-speed
FW's). The exception was a failure in the middle that showed no
indication for its failure with no crack propagation, only a slightly
sloping complete separation and no necking. When it went, it sounded
no different from any other spoke failure, like a small hammer blow on
the hub.

Jobst Brandt

Palo Alto CA
  #7  
Old August 1st 03, 05:16 PM
Peter Cole
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Default Lifetime of spokes?

"Terry Morse" wrote in message
...
Peter Cole wrote:

Spokes never break in the center. 90% of the time they break at the elbow,

the
rest at the threads, that's where the residual manufacturing/building

stresses
are.


Never say never. I've seen a spoke break in the middle before, and
it makes a pretty spectacular noise. The culprit was corrosion,
probably started at a surface scratch.


Sorry, I assumed stainless, I've long discarded anything that isn't. I've also
had a few fail where they were nicked by a chain, but I thought the topic was
fatigue, not accidents or rust.

From:
http://www.duke.edu/~hpgavin/papers/...heel-Paper.pdf

"In 1984 and 1985, fatigue tests on stainless steel bicycle spokes were
carried out for Wheelsmith, Inc. at Stanford University. In 68 spokes the
failure occurred at the cold-worked elbow; in the remaining 8 spokes the
failure occurred at the threads."


  #8  
Old August 1st 03, 08:23 PM
Chris Neary
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Default Lifetime of spokes?


Never say never. I've seen a spoke break in the middle before, and
it makes a pretty spectacular noise. The culprit was corrosion,
probably started at a surface scratch.


Sorry, I assumed stainless, I've long discarded anything that isn't. I've also
had a few fail where they were nicked by a chain, but I thought the topic was
fatigue, not accidents or rust.


Stainless steel isn't immune to all forms of corrosion. Depending on the
grade, stress-corrosion cracking, usually associated with exposure to
chlorides (i.e, sweat or salt air), is a common failure mode.



Chris Neary


"Science, freedom, beauty, adventu what more could
you ask of life? Bicycling combined all the elements I
loved" - Adapted from a quotation by Charles Lindbergh
  #9  
Old August 1st 03, 10:56 PM
Chris Neary
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Default Lifetime of spokes?

Sure, but I don't think bicycle spokes are made from those alloys. Do you?


Well, what are they made of?

I'm guessing a 410 martensitic alloy or similar, which has a number of
corrosion failure modes at room temperature.



Chris Neary

  #10  
Old August 2nd 03, 01:51 AM
Steve McDonald
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Default Lifetime of spokes?


Regardless of the cause of broken spokes, unless you learn to
replace and properly adjust them yourself, your money and time will
continue to be depleted by trips to bike shops. I always carry several
spare spokes taped to the frame and immediately replace broken ones with
the tools from my emergency repair kit. Riding on a wheel with a broken
spoke will stress the remaining spokes next to it and may lead to them
also breaking before long. It's also damaging to the rims and hubs to
run on an out-of-true wheel and will wear out a tire much faster.

Steve McDonald

 




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