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rim life.. questions...



 
 
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  #1  
Old August 28th 05, 07:07 PM
Ravi
external usenet poster
 
Posts: n/a
Default rim life.. questions...

Hi Wheel gurus,
my road bike is a '04 Trek 2100, which came with Bontrager Select
Rims. Recently, when fixing a flat, i noticed there were cracks on the
rear rim near the spoke holes. the rim surface looks like:

===============================================
--o-- o --o-- o
===============================================

'o' is the spoke hole. and '--' is the crack and '==' is the braking
surfaces. This wheel is a 24 spoke wheel and has paired spokes.

The cracks are all on the drive side spokes only. And of the 12 total
drive side spokes, 9 of them had cracks around them (on the rim). I have
put on 10k miles on this wheel.

About me: 6'3" ~190lbs. sometimes i like mash up over small hills, but
usually spin up long grinding hills. i do not race, this is just a
recreational/long distance riding bike.

The LBS examined the wheel and said it was stress related cracks. At the
LBS, I found a '05 Bontrager Select wheel for $120. I would have bought
it, if i had my credit card with me. I decided to return later to buy
it. During this time it got me thinking and few questions:

why failure and why now:
* at ~10k miles, i have 9 cracks on the rims (i wonder when was the
first crack appeared - approx 1000 miles ago ?? probably) in that case
if i were to get a new set of wheels, probably will last only 8k or 9k
miles.
* the rims has no eyelets is that a possible cause for this failure ?
* from the time i bought this bike, only once a spoke came loose and got
it fixed by the LBS and two or three times went out of true and got it
trued by the LBS. Other than that nothing special was made to the Wheel.
Also the rim is offset to accomodate the cassette - so the tension on
the non-drive side wouldn't be as high - to cause this kind of failure.
* paired-spokes is it helping or not helping or hurting the life of wheels.

answers to the above concerns will help me choose one of the following
options:

* buy the '05 Bontrager Select wheel
* get a rim and build up the wheel myself - i haven't examined the
condition of the hub well to see what state it is in. In such a case, i
would have to hunt for a 24h sturdy rim to start with.

recently there has been lots of threads on wheels etc.. i am trying to
catchup on those, but some of my concerns aren't addressed in those.

please provide me your inputs so as to help me decide which way to go...

thanks,
ravi
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  #2  
Old August 28th 05, 07:23 PM
jim beam
external usenet poster
 
Posts: n/a
Default rim life.. questions...

Ravi wrote:
Hi Wheel gurus,
my road bike is a '04 Trek 2100, which came with Bontrager Select
Rims. Recently, when fixing a flat, i noticed there were cracks on the
rear rim near the spoke holes. the rim surface looks like:

===============================================
--o-- o --o-- o
===============================================

'o' is the spoke hole. and '--' is the crack and '==' is the braking
surfaces. This wheel is a 24 spoke wheel and has paired spokes.

The cracks are all on the drive side spokes only. And of the 12 total
drive side spokes, 9 of them had cracks around them (on the rim). I have
put on 10k miles on this wheel.

About me: 6'3" ~190lbs. sometimes i like mash up over small hills, but
usually spin up long grinding hills. i do not race, this is just a
recreational/long distance riding bike.

The LBS examined the wheel and said it was stress related cracks. At the
LBS, I found a '05 Bontrager Select wheel for $120. I would have bought
it, if i had my credit card with me. I decided to return later to buy
it. During this time it got me thinking and few questions:

why failure and why now:
* at ~10k miles, i have 9 cracks on the rims (i wonder when was the
first crack appeared - approx 1000 miles ago ?? probably) in that case
if i were to get a new set of wheels, probably will last only 8k or 9k
miles.
* the rims has no eyelets is that a possible cause for this failure ?
* from the time i bought this bike, only once a spoke came loose and got
it fixed by the LBS and two or three times went out of true and got it
trued by the LBS. Other than that nothing special was made to the Wheel.
Also the rim is offset to accomodate the cassette - so the tension on
the non-drive side wouldn't be as high - to cause this kind of failure.
* paired-spokes is it helping or not helping or hurting the life of wheels.

answers to the above concerns will help me choose one of the following
options:

* buy the '05 Bontrager Select wheel
* get a rim and build up the wheel myself - i haven't examined the
condition of the hub well to see what state it is in. In such a case, i
would have to hunt for a 24h sturdy rim to start with.

recently there has been lots of threads on wheels etc.. i am trying to
catchup on those, but some of my concerns aren't addressed in those.

please provide me your inputs so as to help me decide which way to go...

thanks,
ravi


rim cracks are usually either defective rims [not so common] or excess
spoke tension. sounds like your lbs was over-tensioning if it had been
trued multiple times.

eyelets can be effective local stress mitigation, but even eyeletted
rims crack if spoke tension is still too high.

regarding repair/replacement, replacement is probably the way to go. i
believe you can get rims to repair this wheel, but the economics may not
make a lot of sense. standard rims are not usually available in paired
spoking but you could try a 36h rim skipping every 3rd hole, but spoke
length may be an issue, not to mention drilling offset.

  #3  
Old August 28th 05, 07:24 PM
external usenet poster
 
Posts: n/a
Default rim life.. questions...

On Sun, 28 Aug 2005 11:07:23 -0700, Ravi
wrote:

Hi Wheel gurus,
my road bike is a '04 Trek 2100, which came with Bontrager Select
Rims. Recently, when fixing a flat, i noticed there were cracks on the
rear rim near the spoke holes. the rim surface looks like:

===============================================
--o-- o --o-- o
===============================================

'o' is the spoke hole. and '--' is the crack and '==' is the braking
surfaces. This wheel is a 24 spoke wheel and has paired spokes.

The cracks are all on the drive side spokes only. And of the 12 total
drive side spokes, 9 of them had cracks around them (on the rim). I have
put on 10k miles on this wheel.


[snip]

Dear Ravi,

The spoke tension on the drive side was too high.

Cracks like these are not uncommon when wheels are built to
the highest tension that they can stand without immediately
deforming, a value that can be higher than the rim
manufacturer expects and recommends.

Either get a sturdier rim or reduce the tension.

Carl Fogel
  #5  
Old August 28th 05, 09:15 PM
external usenet poster
 
Posts: n/a
Default rim life.. questions...

On Sun, 28 Aug 2005 19:07:52 GMT, "Sniper Anon"
wrote:


On 28-Aug-2005, wrote:

Dear Ravi,

The spoke tension on the drive side was too high.

Cracks like these are not uncommon when wheels are built to
the highest tension that they can stand without immediately
deforming, a value that can be higher than the rim
manufacturer expects and recommends.

Either get a sturdier rim or reduce the tension.


So Carl, did you perform experiments and analysis to support your argument,
or did you decide to take jim beam's side just to rankle Jobst Brandt?


Dear Snip,

Er, what other explanation besides the spoke tension being
too high for the rim do you offer when the rim cracks around
the base of 9 out of 12 of the higher-tension drive-side
spokes after a few thousand miles?

It's not as if this is a new complaint on this newsgroup.

Jobst's approach of increasing the tension until the wheel
deforms and then backing off was developed with sturdy
36-spoke rims back in the 1980's.

When applied to flimsier, lower-count modern rims, this
practice can lead to cracks around the spoke holes.

To produce the same overall drive-side tension of 18*T that
will cause local yielding with only 12 spokes instead 18,
each spoke has to be tightened to 1.5*T.

Hmmm . . . a 50% increase in tension, cracks appear around
the spoke holes in a few thousand miles, and someone starts
a thread to ask what to do.

This is why Jim Beam keeps suggesting that wheel-builders
should use a tensiometer and tension the spokes to the rim
manufacturer's recommendation.

Carl Fogel
  #6  
Old August 28th 05, 09:29 PM
external usenet poster
 
Posts: n/a
Default rim life.. questions...

Ravi toravir writes:

My road bike is a '04 Trek 2100, which came with Bontrager Select
Rims. Recently, when fixing a flat, I noticed there were cracks on the
rear rim near the spoke holes. the rim surface looks like:


===============================================
--o-- o --o-- o
===============================================


'o' is the spoke hole. and '--' is the crack and '==' is the braking
surfaces. This wheel is a 24 spoke wheel and has paired spokes.


The cracks are all on the drive side spokes only. And of the 12
total drive side spokes, 9 of them had cracks around them (on the
rim). I have put on 10k miles on this wheel.


About me: 6'3" ~190lbs. sometimes I like mash up over small hills,
but usually spin up long grinding hills. I do not race, this is
just a recreational/long distance riding bike.


The LBS examined the wheel and said it was stress related cracks.


That's self evident. What else causes metals to crack in service.

At the LBS, I found a '05 Bontrager Select wheel for $120. I would
have bought it, if I had my credit card with me. I decided to
return later to buy it. During this time it got me thinking and few
questions:


why failure and why now:


* at ~10k miles, I have 9 cracks on the rims (I wonder when was the
first crack appeared - approx 1000 miles ago ?? probably) in that case
if I were to get a new set of wheels, probably will last only 8k or 9k
miles.


* The rims has no eyelets is that a possible cause for this failure
? * from the time I bought this bike, only once a spoke came loose
and got it fixed by the LBS and two or three times went out of true
and got it trued by the LBS. Other than that nothing special was
made to the Wheel. Also the rim is offset to accomodate the
cassette - so the tension on the non-drive side wouldn't be as high
- to cause this kind of failure. * paired-spokes is it helping or
not helping or hurting the life of wheels.


There are several effects coming together that cause these failures.
One is too few spokes another is no steel sockets or eyelets, another
is hard anodizing together with excess tension caused by using too few
spokes. In addition, to accommodate 10-speed gear clusters, rear hubs
have gotten narrower to reduce offset (and the required difference in
tension from left to right). Just the same rear wheels, carry at
least 2/3 the load with the right side spokes. No wonder the rims
develop fatigue cracks.

Before the equipment fad got rolling in the present mode, low spoke
count wheels were used for special events like time trials. Then
professional teams, sponsored by component manufacturers, began using
them on a regular bases, to hell with the expense of frequent
replacement. So here we are with no market for reliable and durable
wheels, most riders being convinced that if Lance Armstrong does it,
it must be what I need.

I am at a loss to suggest what rims you should get but with the hubs
and spokes you have, there is no alternative to shelling out yet more
for the same. Paired spoking, patented by Lovelace in 1890, had no
benefits then and has none now.

For recreational bicycling (oops, that's not PC, we are all on
training rides for our next competition) 36-spoke wheels are still the
reasonable compromise between rim weight and number of spokes. With
low spoke count, one spoke failure will make the wheel unridable but
to make up for that, the spoke cannot be replaced in the field because
such wheels require special fixturing to be tensioned and trued. I
suppose the cell phone has absolved people of touring with tools and
equipment to be self sufficient, so wheels will probably continue to
be as fragile and excessively expensive as most currently are.

It was not long ago that a rider was assured of finding a replacement
rim at most any bicycle shop in the USA or overseas, the standard
being the 36-spoke Mavic MA-2 and other rims that had the same
effective dimensions. I recall rolling into a shop in Italy where we
bought a new MA-2 rim to replace a severely dinged one and no one
thought it was unusual to expect to find one. Most every bicycle
shop had these on the overhead rack.

Jobst Brandt
  #7  
Old August 28th 05, 09:45 PM
external usenet poster
 
Posts: n/a
Default rim life.. questions...

Carl Fogel writes:

The spoke tension on the drive side was too high.


Cracks like these are not uncommon when wheels are built to the
highest tension that they can stand without immediately deforming,
a value that can be higher than the rim manufacturer expects and
recommends.


Either get a sturdier rim or reduce the tension.


So Carl, did you perform experiments and analysis to support your
argument, or did you decide to take jim beam's side just to rankle
Jobst Brandt?


Er, what other explanation besides the spoke tension being too high
for the rim do you offer when the rim cracks around the base of 9
out of 12 of the higher-tension drive-side spokes after a few
thousand miles?


It's not as if this is a new complaint on this newsgroup.


Jobst's approach of increasing the tension until the wheel deforms
and then backing off was developed with sturdy 36-spoke rims back in
the 1980's.


When applied to flimsier, lower-count modern rims, this practice can
lead to cracks around the spoke holes.


Ah yes, "modern" rims. How much e have progressed

To produce the same overall drive-side tension of 18*T that will
cause local yielding with only 12 spokes instead 18, each spoke has
to be tightened to 1.5*T.


Hmmm... a 50% increase in tension, cracks appear around the spoke
holes in a few thousand miles, and someone starts a thread to ask
what to do.


This is why Jim Beam keeps suggesting that wheel-builders should use
a tensiometer and tension the spokes to the rim manufacturer's
recommendation.


That makes little difference. What comes from that is the need for
Loctite on the spoke threads because spokes are now so loose (to not
crack rims) that they slacken in use. It is not unusual to hear spoke
rattle over rougher pavement and that is what unscrews spoke nipples.

At first it was machine built wheels, ones that machines could not
true if made tight as they should be, that introduced thread locking
compounds. Now that we have them, wheels have taken the next step,
that of requiring loose spokes to prevent rims failure and thereby
making thread-lock a necessity. Thread-lock has become the norm in
lieu of reasonably tight wheels because so many have so few spokes.

Jobst Brandt
  #8  
Old August 28th 05, 11:24 PM
external usenet poster
 
Posts: n/a
Default rim life.. questions...

On Sun, 28 Aug 2005 20:45:38 GMT,
wrote:

Carl Fogel writes:

The spoke tension on the drive side was too high.


Cracks like these are not uncommon when wheels are built to the
highest tension that they can stand without immediately deforming,
a value that can be higher than the rim manufacturer expects and
recommends.


Either get a sturdier rim or reduce the tension.


So Carl, did you perform experiments and analysis to support your
argument, or did you decide to take jim beam's side just to rankle
Jobst Brandt?


Er, what other explanation besides the spoke tension being too high
for the rim do you offer when the rim cracks around the base of 9
out of 12 of the higher-tension drive-side spokes after a few
thousand miles?


It's not as if this is a new complaint on this newsgroup.


Jobst's approach of increasing the tension until the wheel deforms
and then backing off was developed with sturdy 36-spoke rims back in
the 1980's.


When applied to flimsier, lower-count modern rims, this practice can
lead to cracks around the spoke holes.


Ah yes, "modern" rims. How much e have progressed

To produce the same overall drive-side tension of 18*T that will
cause local yielding with only 12 spokes instead 18, each spoke has
to be tightened to 1.5*T.


Hmmm... a 50% increase in tension, cracks appear around the spoke
holes in a few thousand miles, and someone starts a thread to ask
what to do.


This is why Jim Beam keeps suggesting that wheel-builders should use
a tensiometer and tension the spokes to the rim manufacturer's
recommendation.


That makes little difference. What comes from that is the need for
Loctite on the spoke threads because spokes are now so loose (to not
crack rims) that they slacken in use. It is not unusual to hear spoke
rattle over rougher pavement and that is what unscrews spoke nipples.

At first it was machine built wheels, ones that machines could not
true if made tight as they should be, that introduced thread locking
compounds. Now that we have them, wheels have taken the next step,
that of requiring loose spokes to prevent rims failure and thereby
making thread-lock a necessity. Thread-lock has become the norm in
lieu of reasonably tight wheels because so many have so few spokes.

Jobst Brandt


Dear Mr. Peabody,

http://www.timetravelreviews.com/tv_...ndsherman.html

Sherman
  #9  
Old August 28th 05, 11:28 PM
jim beam
external usenet poster
 
Posts: n/a
Default rim life.. questions...

wrote:
Carl Fogel writes:


The spoke tension on the drive side was too high.



Cracks like these are not uncommon when wheels are built to the
highest tension that they can stand without immediately deforming,
a value that can be higher than the rim manufacturer expects and
recommends.



Either get a sturdier rim or reduce the tension.



So Carl, did you perform experiments and analysis to support your
argument, or did you decide to take jim beam's side just to rankle
Jobst Brandt?



Er, what other explanation besides the spoke tension being too high
for the rim do you offer when the rim cracks around the base of 9
out of 12 of the higher-tension drive-side spokes after a few
thousand miles?



It's not as if this is a new complaint on this newsgroup.



Jobst's approach of increasing the tension until the wheel deforms
and then backing off was developed with sturdy 36-spoke rims back in
the 1980's.



When applied to flimsier, lower-count modern rims, this practice can
lead to cracks around the spoke holes.



Ah yes, "modern" rims. How much e have progressed


To produce the same overall drive-side tension of 18*T that will
cause local yielding with only 12 spokes instead 18, each spoke has
to be tightened to 1.5*T.



Hmmm... a 50% increase in tension, cracks appear around the spoke
holes in a few thousand miles, and someone starts a thread to ask
what to do.



This is why Jim Beam keeps suggesting that wheel-builders should use
a tensiometer and tension the spokes to the rim manufacturer's
recommendation.



That makes little difference.


using the correct tension makes little difference? it may not make much
difference to wind resistance or stiffness or strength, but it most
definitely makes a difference to fatigue life and rim cracking.

What comes from that is the need for
Loctite on the spoke threads because spokes are now so loose (to not
crack rims) that they slacken in use.


so what about the self-locking nipples that are so easily available?
they don't need loctite. what about the nylock variety used in so many
pre-builts? they don't need loctite either. and even if we /did/ use
loctite, what's wrong with that? it does the job, and judicious use of
a cigarette lighter renders the wheel completely maintainable. if not
more so because the threads are not gummed up with road grit and don't
sieze.

It is not unusual to hear spoke
rattle over rougher pavement and that is what unscrews spoke nipples.


i've never heard that. all i hear is the wind in my ears.


At first it was machine built wheels, ones that machines could not
true if made tight as they should be, that introduced thread locking
compounds. Now that we have them, wheels have taken the next step,
that of requiring loose spokes to prevent rims failure and thereby
making thread-lock a necessity. Thread-lock has become the norm in
lieu of reasonably tight wheels because so many have so few spokes.


an observation of a changing practice is not an observation of a
problem. if you hadn't been advocating spoke tension "as high as the
rim will bear" for so long, we might never have even /had/ pre-built
wheels today because rim manufacturers wouldn't have been so anxious to
get out from under the yoke of frivolous [excess tension] warranty claims.


Jobst Brandt


  #10  
Old August 28th 05, 11:45 PM
external usenet poster
 
Posts: n/a
Default rim life.. questions...

On Sun, 28 Aug 2005 20:29:01 GMT,
wrote:

Ravi toravir writes:

My road bike is a '04 Trek 2100, which came with Bontrager Select
Rims. Recently, when fixing a flat, I noticed there were cracks on the
rear rim near the spoke holes. the rim surface looks like:


===============================================
--o-- o --o-- o
===============================================


'o' is the spoke hole. and '--' is the crack and '==' is the braking
surfaces. This wheel is a 24 spoke wheel and has paired spokes.


The cracks are all on the drive side spokes only. And of the 12
total drive side spokes, 9 of them had cracks around them (on the
rim). I have put on 10k miles on this wheel.


About me: 6'3" ~190lbs. sometimes I like mash up over small hills,
but usually spin up long grinding hills. I do not race, this is
just a recreational/long distance riding bike.


The LBS examined the wheel and said it was stress related cracks.


That's self evident. What else causes metals to crack in service.

At the LBS, I found a '05 Bontrager Select wheel for $120. I would
have bought it, if I had my credit card with me. I decided to
return later to buy it. During this time it got me thinking and few
questions:


why failure and why now:


* at ~10k miles, I have 9 cracks on the rims (I wonder when was the
first crack appeared - approx 1000 miles ago ?? probably) in that case
if I were to get a new set of wheels, probably will last only 8k or 9k
miles.


* The rims has no eyelets is that a possible cause for this failure
? * from the time I bought this bike, only once a spoke came loose
and got it fixed by the LBS and two or three times went out of true
and got it trued by the LBS. Other than that nothing special was
made to the Wheel. Also the rim is offset to accomodate the
cassette - so the tension on the non-drive side wouldn't be as high
- to cause this kind of failure. * paired-spokes is it helping or
not helping or hurting the life of wheels.


There are several effects coming together that cause these failures.
One is too few spokes another is no steel sockets or eyelets, another
is hard anodizing together with excess tension caused by using too few
spokes. In addition, to accommodate 10-speed gear clusters, rear hubs
have gotten narrower to reduce offset (and the required difference in
tension from left to right). Just the same rear wheels, carry at
least 2/3 the load with the right side spokes. No wonder the rims
develop fatigue cracks.

Before the equipment fad got rolling in the present mode, low spoke
count wheels were used for special events like time trials. Then
professional teams, sponsored by component manufacturers, began using
them on a regular bases, to hell with the expense of frequent
replacement. So here we are with no market for reliable and durable
wheels, most riders being convinced that if Lance Armstrong does it,
it must be what I need.

I am at a loss to suggest what rims you should get but with the hubs
and spokes you have, there is no alternative to shelling out yet more
for the same. Paired spoking, patented by Lovelace in 1890, had no
benefits then and has none now.

For recreational bicycling (oops, that's not PC, we are all on
training rides for our next competition) 36-spoke wheels are still the
reasonable compromise between rim weight and number of spokes. With
low spoke count, one spoke failure will make the wheel unridable but
to make up for that, the spoke cannot be replaced in the field because
such wheels require special fixturing to be tensioned and trued. I
suppose the cell phone has absolved people of touring with tools and
equipment to be self sufficient, so wheels will probably continue to
be as fragile and excessively expensive as most currently are.

It was not long ago that a rider was assured of finding a replacement
rim at most any bicycle shop in the USA or overseas, the standard
being the 36-spoke Mavic MA-2 and other rims that had the same
effective dimensions. I recall rolling into a shop in Italy where we
bought a new MA-2 rim to replace a severely dinged one and no one
thought it was unusual to expect to find one. Most every bicycle
shop had these on the overhead rack.

Jobst Brandt


Dear Mr. Peabody,

Posts asking if the MA-2 had been discontinued first
appeared in 1996.

By 1999, some people were even hoarding them:

http://groups.google.com/group/rec.b...7?dmode=source

It's hard to buy rims that haven't been made in this
century.

http://www.timetravelreviews.com/tv_...ndsherman.html

Sherman
 




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