Total wheel Failure



On 6 Jun 2006 21:08:27 -0700, "41" <[email protected]> wrote:

>
>[email protected] wrote:
>> Not mine, but a friends.
>>
>> Your thoughts?
>>
>> Currently the server is slow, so it may take a bit to load.
>>
>> http://bikeforums.net/showthread.php?t=201510
>
>I have not used this rim, but from the pictures, the walls look
>extremely thin. As others have noted, 37mm tires at 85psi is
>unnecessarily, even strangely high, and exerts a lot of force. There
>may have been some contributory defect in the rim, perhaps some
>cracking.
>
>Advice: (1) avoid this rim; (2) what is the point of running 37mm at
>85psi? 32mm at that pressure is already ouch ouch ouch, try 50-60 at
>most, and use a more suitable rim width; (3) ensure spokes properly
>tensioned a la Jobst.
>
>The Velox rim tape held up well though.

Dear 41,

"Wilderness Trail Bikes"

"WTB Slickasaurus 700x37 Hybrid Tire"

"The Slickasaurus is well suited for city streets, gravel, DG, and
hard pack dirt roads. Wire bead, inflate 50-80psi.700x37 Black 460g."

http://www.nashbar.com/profile.cfm?...1246&sku=13703&storetype=&estoreid=&pagename=

So 85 psi on a 50-85 psi tire, but I can't see any mention of what
specific Mavic rim was used on this "36-spoke, 3-cross, custom built,
tensioned, and true" wheel with only 500 miles. Knowing what Mavic rim
was used might show if 85 psi on a 700x37 tire was the culprit.

Cheers,

Carl Fogel
 
[email protected] wrote:
> On 6 Jun 2006 21:08:27 -0700, "41" <[email protected]> wrote:
>
> >
> >[email protected] wrote:
> >> Not mine, but a friends.
> >>
> >> Your thoughts?
> >>
> >> Currently the server is slow, so it may take a bit to load.
> >>
> >> http://bikeforums.net/showthread.php?t=201510
> >
> >I have not used this rim, but from the pictures, the walls look
> >extremely thin. As others have noted, 37mm tires at 85psi is
> >unnecessarily, even strangely high, and exerts a lot of force. There
> >may have been some contributory defect in the rim, perhaps some
> >cracking.
> >
> >Advice: (1) avoid this rim; (2) what is the point of running 37mm at
> >85psi? 32mm at that pressure is already ouch ouch ouch, try 50-60 at
> >most, and use a more suitable rim width; (3) ensure spokes properly
> >tensioned a la Jobst.
> >
> >The Velox rim tape held up well though.
>
> Dear 41,
>
> "Wilderness Trail Bikes"
>
> "WTB Slickasaurus 700x37 Hybrid Tire"
>
> "The Slickasaurus is well suited for city streets, gravel, DG, and
> hard pack dirt roads. Wire bead, inflate 50-80psi.700x37 Black 460g."
>
> http://www.nashbar.com/profile.cfm?...1246&sku=13703&storetype=&estoreid=&pagename=
>
> So 85 psi on a 50-85 psi tire,

Make that 50-80. I have no doubt the tire can take that overload, and
more, but the points are (1) that's more problematic for what appears
to be a terribly thin walled rim destined presumably for 18-25mm,
perhaps 28mm, tires; (2) unless the rider is *well* over 200lbs, or
carrying huge amounts of gear, what is the point of running a 37mm tire
at 85 psi? Machismo, or masochism?
t
 
On 6 Jun 2006 21:35:48 -0700, "41" <[email protected]> wrote:

>
>[email protected] wrote:
>> On 6 Jun 2006 21:08:27 -0700, "41" <[email protected]> wrote:
>>
>> >
>> >[email protected] wrote:
>> >> Not mine, but a friends.
>> >>
>> >> Your thoughts?
>> >>
>> >> Currently the server is slow, so it may take a bit to load.
>> >>
>> >> http://bikeforums.net/showthread.php?t=201510
>> >
>> >I have not used this rim, but from the pictures, the walls look
>> >extremely thin. As others have noted, 37mm tires at 85psi is
>> >unnecessarily, even strangely high, and exerts a lot of force. There
>> >may have been some contributory defect in the rim, perhaps some
>> >cracking.
>> >
>> >Advice: (1) avoid this rim; (2) what is the point of running 37mm at
>> >85psi? 32mm at that pressure is already ouch ouch ouch, try 50-60 at
>> >most, and use a more suitable rim width; (3) ensure spokes properly
>> >tensioned a la Jobst.
>> >
>> >The Velox rim tape held up well though.
>>
>> Dear 41,
>>
>> "Wilderness Trail Bikes"
>>
>> "WTB Slickasaurus 700x37 Hybrid Tire"
>>
>> "The Slickasaurus is well suited for city streets, gravel, DG, and
>> hard pack dirt roads. Wire bead, inflate 50-80psi.700x37 Black 460g."
>>
>> http://www.nashbar.com/profile.cfm?...1246&sku=13703&storetype=&estoreid=&pagename=
>>
>> So 85 psi on a 50-85 psi tire,
>
>Make that 50-80. I have no doubt the tire can take that overload, and
>more, but the points are (1) that's more problematic for what appears
>to be a terribly thin walled rim destined presumably for 18-25mm,
>perhaps 28mm, tires; (2) unless the rider is *well* over 200lbs, or
>carrying huge amounts of gear, what is the point of running a 37mm tire
>at 85 psi? Machismo, or masochism?
>t

Dear 41,

Aaargh! Too many typos today!

Cheers,

Carl Fogel
 
On 6 Jun 2006 11:47:24 -0700, [email protected] wrote:

>Not mine, but a friends.
>
>Your thoughts?
>
>Currently the server is slow, so it may take a bit to load.
>
>http://bikeforums.net/showthread.php?t=201510

I'll weigh in with what I think.

I believe that the first failure was the short break, and I suspect
that an examination of the parting surfaces will reveal that the crack
had started early and had migrated; I'm pretty sure that part of that
surface will show work-polishing indicative of a fracture under
varying stresses. When the crack finally went all the way through,
the rim separated while rotating, one end jammed on a seat stay (I
suspect that the location of the impact will not be hard to identify),
and the sudden cessation of rotation of that end of the band caused
the upward leap as traction and inertia pulled the gap open, wrinkling
the rest of the rim and causing the secondary, larger tear in the
process. The loud bang was the tube blowing out as the gap opened up
between the ends of the failed rim hoop.

The current clock position of the rim in the rear triangle is not
indicative of much of anything; I'm sure it was rotated between the
time of the failure and the time when the photos were taken.

IMO, yes, Mavic owes the bike owner a new wheel.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
 
On Tue, 06 Jun 2006 22:13:32 -0600, [email protected] quoted this
from the Bikeforums site for our pleasure:


>This wheel has failed as I would have expected it to if it had an
>explosive decompression near the valve.
>
>Look carefully. The wheel is in about the same position as when the
>accident occurred. Decompression near the valve (on the road at this
>time) causes a rapid destressing of the rim. The rim "springs out",
>and the elastic shock propogates (via the hub) to the top spokes (near
>the brake), pulling the rim down at the top. See how the top of the
>rim has been flattened, and at least one spoke head (near the label)
>is partially pulled out of the rim. The top spokes are already loaded
>at this time by the weight of the rider - remember, the bike hangs off
>the top spokes. The deformation (flattening) of the top half of the
>rim causes the rim to bulge out in the for/aft positions, ie. to make
>the rim elliptical. It is likely that at this time, the bottom half of
>the rim has elastically rebounded and is therefore contributing to the
>fore/aft elongation.
>
>The result of this is a classical shear failure at the fore/aft
>positions as shown in the photo. We would expect a shear failure would
>be at about 45 degrees, which is exactly what we see. The initiator
>for the shear failures is, as expected, spoke holes, which are the
>local stress raisers.
>
>I see no pre-existing contributor to this failure. It's just plain bad
>luck. You got an explosive blowout just at the point that the wheel
>contacted the ground and all the other dynamics were just not in your
>favour - saddle bouncing, slight road irregularities, pedal torque -
>it all came together at the wrong time.
>
>I could be wrong and I only have the supplied photo to work from,
>however I am an engineer and have done this stuff before. Any other
>engineers care to comment on this failure - an ATSB accident
>investigator would be just dandy!!!
>
>I am interested in what other have to say about this failure. I ride
>on Mavic wheels (MA40's and M193's), weigh 95kg, and have no interest
>in a set of circumstances that may result in the seatpost comming out
>my nostrils!!!
>
>hope this helps,
>JohnF

I agree with the final conclusion, but nothing else about how the
conclusion was reached. I do not believe that any decompression,
sudden or otherwise, could have had the result depicted; the
decompression, IMO, *resulted from* the failure, not the other way
around.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
 
On 6 Jun 2006 11:47:24 -0700, [email protected] wrote:

>Not mine, but a friends.
>
>Your thoughts?
>
>Currently the server is slow, so it may take a bit to load.
>
>http://bikeforums.net/showthread.php?t=201510

Dear D.,

I have to hang this post somewhere . . .

Aha! After swimming through tar to get the bikeforums server to
register, I got in again and found that they've named the rim as a
Mavic CXP33:

TIRE SIZE MAXIMUM PRESSURE
mm bars psi
19 10.00 146.00
23 9.50 138.00
25 9.00 131.00
28 8.00 117.00

http://www.mavic.com/ewb_pages/p/produit_jante_cxp33.php?onglet=3&gamme=route

So it doesn't look as if the rim was meant for 37mm tires. Perhaps
someone can figure out what kind of force 85 psi on a 37mm tire would
be exerting, compared to the widths and maximum pressures above.

It's starting to look like the tire was just too big and the pressure
too high.

Cheers,

Carl Fogel
 
On 6 Jun 2006 21:35:48 -0700, "41" <[email protected]> wrote:

>
>[email protected] wrote:
>> On 6 Jun 2006 21:08:27 -0700, "41" <[email protected]> wrote:
>>
>> >
>> >[email protected] wrote:
>> >> Not mine, but a friends.
>> >>
>> >> Your thoughts?
>> >>
>> >> Currently the server is slow, so it may take a bit to load.
>> >>
>> >> http://bikeforums.net/showthread.php?t=201510
>> >
>> >I have not used this rim, but from the pictures, the walls look
>> >extremely thin. As others have noted, 37mm tires at 85psi is
>> >unnecessarily, even strangely high, and exerts a lot of force. There
>> >may have been some contributory defect in the rim, perhaps some
>> >cracking.
>> >
>> >Advice: (1) avoid this rim; (2) what is the point of running 37mm at
>> >85psi? 32mm at that pressure is already ouch ouch ouch, try 50-60 at
>> >most, and use a more suitable rim width; (3) ensure spokes properly
>> >tensioned a la Jobst.
>> >
>> >The Velox rim tape held up well though.
>>
>> Dear 41,
>>
>> "Wilderness Trail Bikes"
>>
>> "WTB Slickasaurus 700x37 Hybrid Tire"
>>
>> "The Slickasaurus is well suited for city streets, gravel, DG, and
>> hard pack dirt roads. Wire bead, inflate 50-80psi.700x37 Black 460g."
>>
>> http://www.nashbar.com/profile.cfm?...1246&sku=13703&storetype=&estoreid=&pagename=
>>
>> So 85 psi on a 50-85 psi tire,
>
>Make that 50-80. I have no doubt the tire can take that overload, and
>more, but the points are (1) that's more problematic for what appears
>to be a terribly thin walled rim destined presumably for 18-25mm,
>perhaps 28mm, tires; (2) unless the rider is *well* over 200lbs, or
>carrying huge amounts of gear, what is the point of running a 37mm tire
>at 85 psi? Machismo, or masochism?
>t

Dear 41,

I not only got in again, but became a member and posted--took a shower
while waiting for the post to go through, to give you an idea of the
slow-server problem.

Anyway, it turns out to be a 275 lb rider on a CXP33 Mavic rim
recommended only for 19-28mm, running a 37mm tire at 80-85 psi
(estimated):

TIRE SIZE MAXIMUM PRESSURE
mm bars psi
19 10.00 146.00
23 9.50 138.00
25 9.00 131.00
28 8.00 117.00

http://www.mavic.com/ewb_pages/p/produit_jante_cxp33.php?onglet=3&gamme=route

Looks like a heavy rider who mounted too big a tire and then inflated
it too much.

Cheers,

Carl Fogel
 
On Tue, 06 Jun 2006 23:38:07 -0600, [email protected] wrote:

>On 6 Jun 2006 11:47:24 -0700, [email protected] wrote:
>
>>Not mine, but a friends.
>>
>>Your thoughts?
>>
>>Currently the server is slow, so it may take a bit to load.
>>
>>http://bikeforums.net/showthread.php?t=201510
>
>Dear D.,
>
>I have to hang this post somewhere . . .
>
>Aha! After swimming through tar to get the bikeforums server to
>register, I got in again and found that they've named the rim as a
>Mavic CXP33:
>
>TIRE SIZE MAXIMUM PRESSURE
>mm bars psi
>19 10.00 146.00
>23 9.50 138.00
>25 9.00 131.00
>28 8.00 117.00
>
>http://www.mavic.com/ewb_pages/p/produit_jante_cxp33.php?onglet=3&gamme=route
>
>So it doesn't look as if the rim was meant for 37mm tires. Perhaps
>someone can figure out what kind of force 85 psi on a 37mm tire would
>be exerting, compared to the widths and maximum pressures above.
>
>It's starting to look like the tire was just too big and the pressure
>too high.
>
>Cheers,
>
>Carl Fogel

Yes, a quick graph of the 4 sizes and pressures shows a steepening
downward curve for maximum pressure in psi versus width in mm.

The last two points aim at about 65 psi, well below the 80-85 the
rider estimated, and the curve may well drop below that.

I almost went out to lower the rear tire pressure on my ancient Honda
trials machine, since I replaced its original 4x18 tire with an
illegal (for competition) 4.50 monster about 30 years ago, but since
the pressure is only 4-6 psi, I'm going to bed instead.

CF
 
[email protected] wrote:

> On Tue, 06 Jun 2006 19:18:18 -0700, jim beam <[email protected]>
> wrote:
>>
>> judging by the way every spoke hole seems to bulged, i'd say wildly
>> excessive spoke tension had a significant role in this.
>
> Dear Jim,
>
> Can you specify a spoke hole in a picture, say by numbering left to
> right or something like that?
>
> I've looked again, but I can't say that I see bulging at any intact
> spoke hole. No cracking, either.
>
> The curve of the rim's silhouette seems to run quite smoothly to the
> lip of the spoke holes that I see, and then resumes, all without any
> bulging that I notice.

I see what appears to be somewhat diffuse reflections of the spokes on the
rim in the third photo, which might be mistaken for bulging.

--
Benjamin Lewis
 
On Tue, 06 Jun 2006 23:19:33 -0700, Benjamin Lewis
<[email protected]> wrote:

>[email protected] wrote:
>
>> On Tue, 06 Jun 2006 19:18:18 -0700, jim beam <[email protected]>
>> wrote:
>>>
>>> judging by the way every spoke hole seems to bulged, i'd say wildly
>>> excessive spoke tension had a significant role in this.
>>
>> Dear Jim,
>>
>> Can you specify a spoke hole in a picture, say by numbering left to
>> right or something like that?
>>
>> I've looked again, but I can't say that I see bulging at any intact
>> spoke hole. No cracking, either.
>>
>> The curve of the rim's silhouette seems to run quite smoothly to the
>> lip of the spoke holes that I see, and then resumes, all without any
>> bulging that I notice.
>
>I see what appears to be somewhat diffuse reflections of the spokes on the
>rim in the third photo, which might be mistaken for bulging.

Dear Benjamin,

They're faint, but that could explain Jim's theory.

I doubt that it matters any more, since a far more likely explanation
has turned up.

It turns out that the rim was a Mavic CXP33 recommended for up to 28mm
tires running a grossly oversized 37mm tire.

If you graph the maximum pressures against rim width, you'll get 4
points that show a steepening downward curve:

TIRE SIZE MAXIMUM PRESSURE
mm bars psi
19 10.00 146.00
23 9.50 138.00
25 9.00 131.00
28 8.00 117.00

http://www.mavic.com/ewb_pages/p/pro...=3&gamme=route

The last two points, for 25mm/131psi and 28mm/117psi point straight
toward a maximum pressure of about 65 psi at 37mm. (It's actually
probably even lower, since the curve steepens.)

So it's likely that the rim was simply overwhelmed by the force of the
rider's estimated 80-85 psi acting through a 37mm rim, which provides
much more leverage than a narrower rim at the same pressure.

The rider mentions that it had only 500 miles and that he weighs 275.

Cheers,

Carl Fogel
 
I think this logic of too large a tire is wrong as the cause of failure. Logic
dictates it would be an overpreassure situation and by previous threads from the
Mavic website 85psi is no where near an overpreassure situation. Also the rim
should be strong enough to have some safety factor even at +10% of maximum
tire preassure specified. It does not make sense the 38c tire caused or even
contributated. Many have spoken to a very unlikely chain of events causing
this, but in the end even that unlikely chain of events should not have caused
such a cataclysmic failure unless (1) the rim was basically flawed or (2) the
wheel was not built properly. However in the case of (2) the wheel builder has
come forward and I do not believe that the cause.

My 2 cents and I think Mavic should step up and determine conclusively what
happened. This was too catastrophic.

In article <[email protected]>,
[email protected] says...
>
>
>On 6 Jun 2006 11:47:24 -0700, [email protected] wrote:
>
>>Not mine, but a friends.
>>
>>Your thoughts?
>>
>>Currently the server is slow, so it may take a bit to load.
>>
>>http://bikeforums.net/showthread.php?t=201510
>
>Dear D.,
>
>I have to hang this post somewhere . . .
>
>Aha! After swimming through tar to get the bikeforums server to
>register, I got in again and found that they've named the rim as a
>Mavic CXP33:
>
>TIRE SIZE MAXIMUM PRESSURE
>mm bars psi
>19 10.00 146.00
>23 9.50 138.00
>25 9.00 131.00
>28 8.00 117.00
>
>http://www.mavic.com/ewb_pages/p/produit_jante_cxp33.php?
onglet=3&gamme=route
>
>So it doesn't look as if the rim was meant for 37mm tires. Perhaps
>someone can figure out what kind of force 85 psi on a 37mm tire would
>be exerting, compared to the widths and maximum pressures above.
>
>It's starting to look like the tire was just too big and the pressure
>too high.
>
>Cheers,
>
>Carl Fogel
 
However, to add to my previous post, if the rider is 275 lb then that could easily
be well beyond Mavic's specifications for the rim.

I would value Jobst's or Sheldon's thoughts on this wheel failure.

In article <[email protected]>,
[email protected] says...
>
>
>I think this logic of too large a tire is wrong as the cause of failure. Logic
>dictates it would be an overpreassure situation and by previous threads from
the
>Mavic website 85psi is no where near an overpreassure situation. Also the rim
>should be strong enough to have some safety factor even at +10% of
maximum
>tire preassure specified. It does not make sense the 38c tire caused or even
>contributated. Many have spoken to a very unlikely chain of events causing
>this, but in the end even that unlikely chain of events should not have caused
>such a cataclysmic failure unless (1) the rim was basically flawed or (2) the
>wheel was not built properly. However in the case of (2) the wheel builder has
>come forward and I do not believe that the cause.
>
>My 2 cents and I think Mavic should step up and determine conclusively what
>happened. This was too catastrophic.
>
>In article <[email protected]>,
>[email protected] says...
>>
>>
>>On 6 Jun 2006 11:47:24 -0700, [email protected] wrote:
>>
>>>Not mine, but a friends.
>>>
>>>Your thoughts?
>>>
>>>Currently the server is slow, so it may take a bit to load.
>>>
>>>http://bikeforums.net/showthread.php?t=201510
>>
>>Dear D.,
>>
>>I have to hang this post somewhere . . .
>>
>>Aha! After swimming through tar to get the bikeforums server to
>>register, I got in again and found that they've named the rim as a
>>Mavic CXP33:
>>
>>TIRE SIZE MAXIMUM PRESSURE
>>mm bars psi
>>19 10.00 146.00
>>23 9.50 138.00
>>25 9.00 131.00
>>28 8.00 117.00
>>
>>http://www.mavic.com/ewb_pages/p/produit_jante_cxp33.php?
>onglet=3&gamme=route
>>
>>So it doesn't look as if the rim was meant for 37mm tires. Perhaps
>>someone can figure out what kind of force 85 psi on a 37mm tire would
>>be exerting, compared to the widths and maximum pressures above.
>>
>>It's starting to look like the tire was just too big and the pressure
>>too high.
>>
>>Cheers,
>>
>>Carl Fogel
>
 
[email protected] wrote:
> Aha! After swimming through tar to get the bikeforums server to
> register, I got in again and found that they've named the rim as a
> Mavic CXP33:
>
> TIRE SIZE MAXIMUM PRESSURE
> mm bars psi
> 19 10.00 146.00
> 23 9.50 138.00
> 25 9.00 131.00
> 28 8.00 117.00

There is a more general document that completes data :
19 10,0 146
23 9,5 138
25 9,0 131
28 8,0 117
32 7,0 103
35 6,0 88
http://www.tech-mavic.com/tech-mavi...te/GalRouePiste/Recommended_Tire_Pressure.pdf
or http://minilien.com/?dlX45Auply
So 85 psi in a 37mm tyre is on the high side but still within normal
use (as would be 135psi in a 23mm tyre, and isn't that quite common for
a 200lb+ rider?). I personnally sees that as a good compromise between
rolling resistance and comfort, btw.

Considering the original question, I would point out the fact that the
fore failure (wheel3.jpg) has the eyelet pulled out, but have no
particular idea of what caused it... Impressive!
 
[email protected] wrote:
> > > Your thoughts?
> > Surely someone . . . .??
> To confuse things even more, there is now an additional thread on this
> at BFN

I am not pretending to say something new, since I have not gone through
the whole lot of these posts, but let me voice it anyhow.

I believe it was caused by failure of the side wall of the rim, alas
too thin and fragile.
I have myself seen some Ambrosio Excellence Extralight (or Superlight?)
rim failing there with no sensible reason, other than it being
underdimensioned.

Sergio
Pisa
 
John Forrest Tomlinson <[email protected]> wrote:

> What pressure is used in those Nokians?
>
> I'm guessing that 85psi is on the high side for 37mm tires. I have
> some 28s and 85 or 95psi is the max for them, and they hold a lot less
> air than 37s can.

Maximum pressure recommended by the manufacturer is 4.5 bar (65 psi),
but I think many people use pressures lower than that. It depends on the
conditions.

-as
 
[email protected] wrote:
> There is a more general document that completes data :
> ?19 10,0 146
> 23 9,5 138
> 25 9,0 131
> 28 8,0 117
> 32 7,0 103
> 35 6,0 88
> http://www.tech-mavic.com/tech-mavi...te/GalRouePiste/Recommended_Tire_Pressure.pdf
> or http://minilien.com/?dlX45Auply
> So 85 psi in a 37mm tyre is on the high side but still within normal
> use

It is OK for a 275lb rider, but insane for e.g. a 150lb rider. The
questions though are still (a) whether such a rim, as spec'd above, can
take the next data point of 37mm/85psi with a 275lb rider; and (b)
whether Mavic's specs as above are indeed realistic for the strength
and durability of the rim, and the size of the rider. A bump may have
been encountered earlier, causing a crack and leading to the
catastrophic failure JRA.

If we plot hoop force per unit length as caculated by a previous poster
as P*R, versus tire size, the results are not a horizontal line. The
figures (force in megaN) are:

mm psi mN
19 146 9.56 (spec)
23 138 10.94 (spec)
25 131 11.29 (spec)
28 117 11.29 (spec)
35 88 10.62 (spec)
37 85 10.84 (catastrophic failure)

and the plot is an assymetric inverted U, except for the last one which
hooks up. Still within the overall band, but inconsistent with the
trend. The variation in force per unit length for all of these is
within a ±10% band around the average. Still, since Mavic pointedly
chooses the specs so as NOT to have a constant force per unit length as
calculated above, they must be looking at some other factor, and
whatever that is, the 37mm/85psi is clearly off the trend. If it were
on an inverted U trend, the max psi would be about 80 with the 35/88
spec included, and about 75 psi if the 35/88 were not included, so as
to make the U symmetric. Then there is that 275lb rider on a
thin-walled racing rim.

Solution: (a) don't use that rim with that tire at that pressure and
that rider weight; (b) don't use that rim. I suggest the rider needs a
500+ g rim, such as at minimum an Ambrosio Evolution (480g, 13.5mm
ERTRO width, <http://www.ambrosiospa.com/cerchi_corsa.htm>), much
better an Ambrosio Keba (610g, 18mm ERTRO width,
<http://www.ambrosiospa.com/touring.htm>).
 
Benjamin Lewis wrote:
> [email protected] wrote:
>
>
>>On Tue, 06 Jun 2006 19:18:18 -0700, jim beam <[email protected]>
>>wrote:
>>
>>>judging by the way every spoke hole seems to bulged, i'd say wildly
>>>excessive spoke tension had a significant role in this.
>>
>>Dear Jim,
>>
>>Can you specify a spoke hole in a picture, say by numbering left to
>>right or something like that?
>>
>>I've looked again, but I can't say that I see bulging at any intact
>>spoke hole. No cracking, either.
>>
>>The curve of the rim's silhouette seems to run quite smoothly to the
>>lip of the spoke holes that I see, and then resumes, all without any
>>bulging that I notice.
>
>
> I see what appears to be somewhat diffuse reflections of the spokes on the
> rim in the third photo, which might be mistaken for bulging.
>
no mistake. the anodizing clouds where the rim deforms, hence the
"diffuse reflections".
 
-----BEGIN PGP SIGNED MESSAGE-----

In article <[email protected]>,
41 <[email protected]> wrote:
>

>
>Make that 50-80. I have no doubt the tire can take that overload, and
>more, but the points are (1) that's more problematic for what appears
>to be a terribly thin walled rim destined presumably for 18-25mm,
>perhaps 28mm, tires; (2) unless the rider is *well* over 200lbs, or
>carrying huge amounts of gear, what is the point of running a 37mm tire
>at 85 psi? Machismo, or masochism?
>t
>

_ The rider is well over 200lbs, 275 per the original
thread. There are some interesting comments in there from
the wheel builder. He claims to have used a tensionmeter
and the wheel was within Mavics spoke tension tolerances
(ie. under 100kgs ). This paraphased comment I found puzzling.

The cxp33 was the strongest rim we could find.

My guess was he didn't look too hard.

_ Booker C. Bense


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On 7 Jun 2006 02:18:05 -0700, [email protected] wrote:

>Considering the original question, I would point out the fact that the
>fore failure (wheel3.jpg) has the eyelet pulled out, but have no
>particular idea of what caused it... Impressive!

The break in the rim at that point crosses the eyelet hole. This is
part of the reason that I believe that this was the first failure
point. If, as I suspect, the crack began at the hole and migrated
outward and across the inner web before the final failure, the rest
follows logically.
--
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