Total wheel Failure
dnv...@aol.com
Your thoughts?
Currently the server is slow, so it may take a bit to load.
dnv...@aol.com
I forgot to mention that there are pics, and that this is a pretty
unique wheel failure.
Surely someone . . . .??
carl...@comcast.net
Dear D.,
Your friend's wheel failure is so lurid that I'm shamelessly posting
links to the pictures and copying your friend's text, since your
server is slow and there's some prejudice against bikeforums:
http://members.cox.net/younggg/Wheel1.jpg
http://members.cox.net/younggg/Wheel2.jpg
http://members.cox.net/younggg/Wheel3.jpg
****
Facts are as follows:
This wheel was 36-spoke, 3-cross, custom built, tensioned, and true.
The wheel had about 500 miles on it when it detonated.
The tire was a WTB Slickisaurus 700x37c inflated to (Mfg. recommended)
85 psig.
The tube showed about a 9-inch-long smooth split on the spoke-side of
the tube.
The rim tape was not punctured
The wheel detonated with a bang on smooth pavement at about 19 mph
The rim did NOT fail at the weld - the weld is still intact.
The wheel bead showed no signs of damage other than where it was
punctured by the broken rim
The LBS does NOT think this was caused by the bead coming loose from
the rim (their opinion)
Questions:
What caused this rim to fail?
What can I do to prevent this from happening again? (I'm lucky to be
alive)
Does Mavic owe me another wheel?
I have three other wheels with the same rims - am I at risk from them
too?
***
Cheers,
Carl Fogel
dnv...@aol.com
If you read the entire thread, there is additional information
including some statements from the actual wheel builder, who is very
involved in trying to figure out the cause of this "unique" failure.
Martin Borsje
- any hole in the ground?
- sewer cover?
- grating?
- tram rail?
Have a CXP 33 myself as well (4 pcs) lasted 6000 / 500 km yet and still
counting.
--
Posted by news://news.nb.nu
Llatikcuf
Wow, when the rim cracked it blew the seat off too!
-nate
dnv...@aol.com
I would refer you to the thread, where all of this and more is
discussed in some detail. As I understand it, smooth pavement, 19 mph,
BLOOEY!
> Posted by news://news.nb.nu
dnv...@aol.com
I quote from the thread and the person to whom this happened:
"What were you doing when the wheel broke?
I was riding on smooth pavement at 19mph. I was about 40 minutes into
my daily ride. No potholes, no debris - smooth pavement.
What did you hit or what hit you?
No collision whatsoever. One moment everything was normal, the next, I
was sliding down the road on my butt. I believe when the wheel
detonated, I was thrown up. When I came down, the seatpost bolt broke
and dumped me off the back of the bike. Luckily, I didn't land on the
seatpost or the broken rim or I'd not be here now.
Why does the wheel appear to be too big for the bike?
Must be an artifact of the photo - the bike is a Klein Navigator
touring frame made for (and with clearance for) the 700x37c tires that
are on the bike."
Ron Ruff
dnv...@aol.com wrote:
> No collision whatsoever. One moment everything was normal, the next, I
> was sliding down the road on my butt. I believe when the wheel
> detonated, I was thrown up. When I came down, the seatpost bolt broke
> and dumped me off the back of the bike.
There is a possibilty that he struck something (unseen) with the rear
wheel.
Also note that the rim (CXP33) is designed for <28mm tires, but a 37mm
was mounted.
Antti Salonen
> Also note that the rim (CXP33) is designed for <28mm tires, but a 37mm
> was mounted.
A lot of people use 37 mm or wider tyres on road rims, especially on
cyclocross bikes. Perhaps the most common example seen here in the
winter is the Nokian W240 studded tyre, size 40-622. Usually the wider
the tyre the lower the pressure, so the rim should be fine.
-as
o...@ozarkbicycleservice.com
Never underestimate the power of compressed air when freed from it's
bonds! ;-)
John Forrest Tomlinson
<antti....@helsinki.if.invalid> 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.
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************
Michael Press
<1149621496.6...@h76g2000cwa.googlegroups.com>,
dnv...@aol.com wrote:
There's your problem. It's that little yellow patch at
10 o'clock.
Good pictures. Thanks for sharing. Hope the rider is well.
--
Michael Press
Michael Press
<1149619643....@c74g2000cwc.googlegroups.com>,
dnv...@aol.com wrote:
Only one wildly improbable scenario for a JRA failure. The
7 o'clock fracture looks like the spoke pulled the eyelet
through the rim, and then the rim collapsed around the
hole.
--
Michael Press
jason...@gmail.com
<snip>
> Usually the wider
> the tyre the lower the pressure, so the rim should be fine.
>
> -as
Hi Antti,
Don't forget that the force exerted by the tire on the rim scales with
the radius of the tire section (that is, with the surface area of the
casing). A wide tire at lowish pressure can exert more force at the
bead/rim interface than a 700x18 tire at 150 psi.
Hoop stress in a cylindrical pressure vessel is PR/T where P is
pressure, R is the cylinder radius and T is the thickness of the
material. Since we're concerned about force and not stress (which is
force/area), we can dispense with the denominator. This leaves us with
PR.
For an 18mm (0.009 m radius) tire pumped to 150 psi (1.03 megaPascals)
we get a force of 9270N per unit length*,
For a 37 mm (0.0185 m radius) tire pumped to 85 psi (0.59 MPa) we get a
force of 10,915N per unit length--obviously, a larger force.
When one considers a 23mm tire pumped to 115 psi (perhaps the most
common numbers), we get a result of 9118N per unit length.
This calculation incorporates a number of assumptions. I've assumed
that nominal tire width is actual width and that toroidal pressure
vessels (i.e., tires) operate exactly like cylindrical pressure
vessels. However, the forces I've listed should be pretty accurate on a
relative scale.
The point is that low-pressure fat tires can and do exert higher forces
on rims at the bead interface than do high-pressure skinny tires.
This is a very strange failure to me. I'll be interested to hear what
the cause was.
Cheers,
Jason
* N.B.: A Pascal is a unit of pressure, specifically, a force of one
Newton per square meter. Since P*R is (N/m^2)*m, the unit of radius
cancels with one of the units of area, yielding force (Newtons) per
meter.
jim beam
judging by the way every spoke hole seems to bulged, i'd say wildly
excessive spoke tension had a significant role in this.
waxbytes
carl...@comcast.net
... and there's some prejudice against bikeforums...
Cheers,
Carl Fogel[/QUOTE Wrote:
>
>
> Just curious, why is there a predjudice against bikeforums?
--
waxbytes
carl...@comcast.net
<waxbyte...@no-mx.forums.cyclingforums.com> wrote:
>
>.. and there's some prejudice against bikeforums...
>
>
>Cheers,
>
>Carl Fogel[/QUOTE Wrote:
>>
>>
>> Just curious, why is there a predjudice against bikeforums?
Dear Waxbytes,
There you take me into dark waters.
Some hint at snobbery, others at xenophobia. Newsgroups often attract
an unpleasant element.
I suppose that it's comforting to some of the more insecure RBT
posters to rail at what they enjoy calling newbies.
Admittedly, the abominable slowness of the server does nothing to
endear bikeforums to strangers. Let me try again . . .
http://bikeforums.net/showthread.php?t=201510
No, I still can't get in. I did manage to get in earlier today,
shortly after the original post appeared in RBT, but only once.
Luckily, I knew enough to grab everything that wasn't nailed down and
dumped the swag here in RBT, where I suspect bulging-eyed regulars are
staring at the juicy bike-failure porn reproduced again below. The
pictures are on some other server and come up quite quickly.
Cheers,
Carl Fogel (picture links and pirated text below)
carl...@comcast.net
wrote:
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.
Cheers,
Carl Fogel
41
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.
carl...@comcast.net
Dear D.,
Bikeforums seems to be working more quickly now, so I got in and saw
one theory (post#21) that might interest RBT posters, particularly the
part about the bike hanging off its top spokes.
Cheers,
Carl Fogel
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
carl...@comcast.net
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."
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
41
carlfo...@comcast.net wrote:
> On 6 Jun 2006 21:08:27 -0700, "41" <KingGe...@yahoo.fr> wrote:
>
> >
> >dnv...@aol.com 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?category=&subcategory=&brand=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
carl...@comcast.net
Dear 41,
Aaargh! Too many typos today!
Cheers,
Carl Fogel
Werehatrack
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.
Werehatrack
from the Bikeforums site for our pleasure:
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.
carl...@comcast.net
>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
carl...@comcast.net
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
carl...@comcast.net
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
Benjamin Lewis
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
carl...@comcast.net
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
RS
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 <t7pc82p3paens4a15...@4ax.com>,
carl...@comcast.net says...
RS
be well beyond Mavic's specifications for the rim.
I would value Jobst's or Sheldon's thoughts on this wheel failure.
In article <uYOdnTYgtbuZ7xvZ...@comcast.com>,
r_sch...@comcast.net says...
dnv...@aol.com
dnv...@aol.com wrote:
> dnv...@aol.com 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
>
> unique wheel failure.
>
To confuse things even more, there is now an additional thread on this
at BFN
nikojorj_ja...@yahoo.fr
carl...@comcast.net 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-mavic/uk/sources/Produits/Piste/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!
serv...@df.unipi.it
dnv...@aol.com 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
Antti Salonen
> 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
41
nikojorj_ja...@yahoo.Fr wrote:
> There is a more general document that completes data :
> 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-mavic/uk/sources/Produits/Piste/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>).
jim beam
"diffuse reflections".
Booker C. Bense
In article <1149654948....@y43g2000cwc.googlegroups.com>,
41 <KingGe...@yahoo.fr> 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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Werehatrack
>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.
dnv...@aol.com
replacement and continue riding?
dnv...@aol.com
dnvr...@aol.com wrote:
> How many of you would put an identical wheel/tire/pressure in as a
> replacement and continue riding?
Let me change that a bit.
A quote from the person for whom the wheel failed:
"The bike is now in the shop for inspection & repair. The dead wheel is
packed for return to Rev. Chuck who will do some in-depth analysis of
the failure. I've closely inspected the remaining three wheels built
with identical components - none show signs of cracking or distress. I
guess I'll be using the remaining wheels unless there's a good reason
not to? "
Your reaction to that statement?
Pat Lamb
You may be right, it's hard to tell with just these pictures to work
from. I'll offer the contrary theory here, just in case you're wrong. ;)
I suspect there was an incipient failure at the spoke hole at the middle
of the longer break; note the crosswise crack at the upper half of the
spoke in the second picture. When this crack propagated far enough, it
failed catastrophically, leaving the rim sidewalls to carry the entire
compressive load. The sidewalls folded inward, with the bottom side
failing outward, which the hoop stress then folded back. (Note this
could be the site of the "tire-pumped-up-too-much" failure, but I don't
see how that would create the diagonal tear across the rim anchored at
one end of the tear.) I suspect the short tear was caused by the wheel
folding over across the diameter from the original break.
I'm not sure if the rim tape tear at the top is significant or not. It
tells me the top tear was from the left side, which indicates (but
doesn't conclusively prove) the sidewall blowout was secondary to the
rim failure. However, if you're right about the first failure happening
at the short tear on the bottom, it's merely an interesting sidebar.
I agree the current position is meaningless. Severely bent spokes occur
around 120 degrees of the wheel. Those had to drag against something
(dropout?) while the wheel was rotating/decelerating.
The guy is owed a wheel. Maybe from the builder, if he overtensioned
the spoke leading to failure. Maybe from Mavic, otherwise.
Pat
carl...@comcast.net
>How many of you would put an identical wheel/tire/pressure in as a
>replacement and continue riding?
Dear D.,
I wouldn't put a 37mm tire on a rim recommended for no more than 28mm
and 117 psi and then blow it up to an estimated 80-85 psi,
particularly if I weighed 275 lbs.
I've heard of a case where the wheel failed catastrophically within
500 miles on smooth pavement when this was done.
Cheers,
Carl Fogel
dnv...@aol.com
How about a 28mm tire?
carl...@comcast.net
Dear D.,
I'd happily put a 28mm tire on a rim rated for that width with no more
than 117 psi--and inflate it to about 100 psi or less. A recommended
maximum is a warning, not an invitation to see what happens.
In any case, the destroyed rim was wearing a 37mm tire inflated to an
estimated 80-85 psi when it abruptly tore itself in half after only
500 miles.
That 37mm is 32% beyond the CXP33's maximum recommended width.
What could be a more impressive and dramatic illustration that Mavic
was right about those rim limits? Or that wider tires exert more
leverage on rims?
Cheers,
Carl Fogel
dnv...@aol.com
And weighing 275 pounds you would ride happily into the sunset with a
28mm at 117 psi. Never a 2nd thought?
mrbubl
dnv...@aol.com
You ,missed the point of the question, which was, "Would you go out on
THOSE rims (the rim-type that failed so catastrophically) at 117psi,
28mm and 275 pounds."
Perhaps you haven't read the thread?
It was NOT about 36 spoke wheels.
you...@cox.net
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>).
Hi! I'm the clydesdale whose Mavic blew up, instigating this thread.
I'm planning on having all my wheels rebuilt with different rims (I'm
scared of those Mavics now...). I'm not familiar with Ambrosio rims.
I note that Ambrosio offers multiple "touring" rims with wider
profiles. What differences are there between the different Ambrosio
touring rims, and which is the strongest?
Thanks!
Sandy
> mrbubl wrote:
>>> And weighing 275 pounds you would ride happily into the sunset with a
>>> 28mm at 117 psi. Never a 2nd thought?
>>>
>>>
>> Yup and do everyday....Michelin carbons on velocity aero 36 spoke
>>
>
> You ,missed the point of the question, which was, "Would you go out on
> THOSE rims (the rim-type that failed so catastrophically) at 117psi,
> 28mm and 275 pounds."
>
> Perhaps you haven't read the thread?
>
> It was NOT about 36 spoke wheels.
>
stiff, keep true, work well.
But to look more closely, the first thing to do is lose at least 75 pounds.
Easier to blame equipment, I guess. Ride enough, and there's no need
for that Q,
dnv...@aol.com
You are confusing me and the person for whom the wheel failed. But, I
guess it is not the first time I have been mistaken for someone else,
nor likely the last!
PTL, I only weigh about 220 lbs, and my Mavics on my Lemond have held
up just fine for 8 years now.
But, thanks for your kind thoughts.
Sandy
you...@cox.net
> > I'm planning on having all my wheels rebuilt with different rims
> Briefly, that would be dumb and wasteful
Why? If the Mavics have quality control problems, isn't it possible
that the remaining rims could likely fail also? If I could
definitively establish that excess tire width was the root-cause of
this wheel failure, I'd be happy to continue using the Mavics with tire
sizes recommended by Mavic. Unfortunately, I don't think that has been
established (nor do I think it can be). I'm left with wheels that I
can't trust. So let's cut to the chase - why do you think my decision
to replace the Mavic rims is dumb and wasteful? Thanks!
sal bass
but why haven't there been issues with the DT Swiss RR 1.1 rims
(622-15) being used with 30 mm + wide cyclocross tires?
this seems a most extreme example.
i know of at least 13 riders who race for a shop. all on the 1.1 rims
with a kevlar beaded Maxxis Locust CX tire (35mm). they've been using
this rim and tire combo for almost a year now....and some even do urban
rides without swapping out to a smoother tire.
jason...@gmail.com wrote:
> Antti Salonen wrote:
>
> <snip>
>
> > Usually the wider
> > the tyre the lower the pressure, so the rim should be fine.
> >
> > -as
>
> Hi Antti,
>
> Don't forget that the force exerted by the tire on the rim scales with
> the radius of the tire section (that is, with the surface area of the
> casing). A wide tire at lowish pressure can exert more force at the
> bead/rim interface than a 700x18 tire at 150 psi.
>
> Hoop stress in a cylindrical pressure vessel is PR/T where P is
> pressure, R is the cylinder radius and T is the thickness of the
> material. Since we're concerned about force and not stress (which is
> force/area), we can dispense with the denominator. This leaves us with
> PR.
>
> For an 18mm (0.009 m radius) tire pumped to 150 psi (1.03 megaPascals)
> we get a force of 9270N per unit length*,
>
> For a 37 mm (0.0185 m radius) tire pumped to 85 psi (0.59 MPa) we get a
> force of 10,915N per unit length--obviously, a larger force.
>
> When one considers a 23mm tire pumped to 115 psi (perhaps the most
> common numbers), we get a result of 9118N per unit length.
>
> This calculation incorporates a number of assumptions. I've assumed
> that nominal tire width is actual width and that toroidal pressure
> vessels (i.e., tires) operate exactly like cylindrical pressure
> vessels. However, the forces I've listed should be pretty accurate on a
> relative scale.
>
> The point is that low-pressure fat tires can and do exert higher forces
> on rims at the bead interface than do high-pressure skinny tires.
>
> This is a very strange failure to me. I'll be interested to hear what
> the cause was.
>
>
> Cheers,
>
> Jason
>
>
> * N.B.: A Pascal is a unit of pressure, specifically, a force of one
> Newton per square meter. Since P*R is (N/m^2)*m, the unit of radius
> cancels with one of the units of area, yielding force (Newtons) per
> meter.
carl...@comcast.net
Dear D.,
You may have missed my reply:
>> I'd happily put a 28mm tire on a rim rated for that width with no more
>> than 117 psi--and inflate it to about 100 psi or less. A recommended
>> maximum is a warning, not an invitation to see what happens.
I've missed even plainer replies, so don't worry about it.
Cheers,
Carl Fogel
Benjamin Lewis
> Benjamin Lewis wrote:
>> 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".
Heh. Nice try.
--
Benjamin Lewis
jim beam
effects of deformation then ben? don't be coy.
Benjamin Lewis
Why bother? Anyone who chooses to do so may view the photos for themselves.
--
Benjamin Lewis
Hank Wirtz
news:1149718074....@y43g2000cwc.googlegroups.com:
Not an answer to your question, but another vote for Ambrosio. I weigh
240 and my daily commuter wheels are Ambrosio Excursions, which are the
same rim as the Evolution, but without the machined sidewalls. As a
consequence, they're slightly heavier (510g vs 480g) but that material's
in the sidewall where you need it. It's also socketed for better
distribution of spoke tension than single- or non-eyeleted rims.
I run them with 28mm Continental GP4Season tires @ 90-105psi. I've also
had 32mm Kenda Kwick cyclocross tires on them at around 55-60psi.
I've put close to 1000 miles on them since I built them in February, and
when I had the rear tire off to change a flat this weekend, I threw it
in the truing stand to touch it up. I was astonished that it was still
perfectly true, since I hadn't looked at it since I built it. Threw the
front in the stand, same thing. Nice wheels.
Werehatrack
<bbense+rec.bicycl...@telemark.slac.stanford.edu> wrote:
>... 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.
Uh, yeah. Maybe the strongest he could find in the stockroom that
afternoon?
Phil, Squid-in-Training
Carl, have you ever seen this type of failure before?
How many large people in the world put 37mm tires on their CXP33s, and pump
them up to 85psi? I am willing to bet more than one.
IMO, this is a manufacturing defect.
--
Phil
G.T.
>>>I'm planning on having all my wheels rebuilt with different rims
>
>
>>Briefly, that would be dumb and wasteful
>
>
> Why? If the Mavics have quality control problems, isn't it possible
> that the remaining rims could likely fail also?
Ignore him. He's a Francoshill.
Greg
--
"All my time I spent in heaven
Revelries of dance and wine
Waking to the sound of laughter
Up I'd rise and kiss the sky" - The Mekons
G.T.
I'm not 275 but I've been know to run fat tires at high pressure on
narrow rims. I never thought they'd just blow up. In fact I never
thought they'd even fail. I guess MA-2s were made when Mavic still had
quality control.
carl...@comcast.net
Dear Phil,
No, I've never seen a rim tear itself into two pieces on a smooth
piece of pavement. No one else who's posted has mentioned seeing such
as thing, either, though I expect there are riders who have indeed
seen such failures.
I think that you'd lose your bet.
Think about why Mavic clearly shows safe recommended rim pressures
declining from 146 psi to 117 psi as tire width increases from 19 to
28 mm:
http://www.mavic.com/ewb_pages/p/produit_jante_cxp33.php?onglet=3&gamme=route
Going to a 37mm is about 32% off the manufacturer's scale. Draw a
graph of the four data points, and you get a steeper and steeper
curve. A line drawn between the last two points indicates that 65 psi
would be the maximum safe pressure for a 37mm tire--and that's a
straight line, not the actual diving curve. Any spreadsheet will show
this in a few minutes. Slap a ruler on the last two data points and
see where it ends up over 37mm.
Here's a cross-section diagram of the CXP33:
http://www.lickbike.com/productpage.aspx?PART_NUM_SUB='2104-28'
On my screen, the "19.4mm" exterior width measures 41mm, while the
unlabeled interior width measures 29.5mm.
Scaling indicates that the interior width is only 14mm.
Here's Georg Boeger's well-respected German tandem site's rim/tire
size chart, way up near the top of the page:
http://tandem-fahren.de/Technik/Reifentips/index.html
Here's the edited version, way down on Sheldon's page:
http://www.sheldonbrown.com/tire_sizing.html
If dimension "a" is 14mm (between 13 and 15), then Boeger estimates
that a 37mm tire is about 3 bombs to the right on the warning scale.
The bombs aren't a joke--that's how the an aluminum rim will fail when
overstressed by the leverage of the wrong tire inflated too high. It's
basically a thin-walled pressure vessel.
The rim section under the hub is squashing out abruptly to the sides
as its center flattens at the contact patch. Then it "relaxes" and
spins around again for the next stress rise.
All the time, it's under the tremendous expansion pressure of the
inner tube.
Eventually, ka-boom! About 500 miles in this case.
The wider the bicycle tire and the narrower the rim, the lower the
safe inflation pressure.
Add a rider who weighs twice as much as you do, and 500 miles later
the rim fails dramatically, just as expected.
Darned few riders weighing 265 lbs are likely to be putting 37mm tires
at 80-85 psi on such a narrow rim. The ones who do are going to find
out the hard way that it's a very bad idea.
The posters who are surprised are generally riding 35mm or smaller
tires (that 2mmm matters), using 75% or less as much pressure (20 to
40 psi makes a big difference down that low), and don't weigh 265 lbs
(60 to 130 pounds less is a considerable change).
As I've said before, can you think of a more dramatic illustration of
the warnings about tire width and inflation?
Cheers,
Carl Fogel
41
you...@cox.net wrote:
> I suggest the rider needs a 500+ g rim, such as at minimum an Ambrosio
> Evolution (480g, 13.5mm
>
> Hi! I'm the clydesdale whose Mavic blew up, instigating this thread.
> I'm planning on having all my wheels rebuilt with different rims (I'm
> scared of those Mavics now...). I'm not familiar with Ambrosio rims.
> I note that Ambrosio offers multiple "touring" rims with wider
> profiles. What differences are there between the different Ambrosio
> touring rims, and which is the strongest?
The person you really want to correspond with is Chalo Cholina of this
forum, the heaviest serious rider on the internet, if not the planet.
On the way to that distinction he spent enough time at your weight to
know exactly what will last and what will not. You will find Ambrosio
rims a little hard to come by in the US, and I believe he uses Sun
rims. These come or at least used to come in suitably strong models
(CR-18, CR-16, Rhyno and Rhyno Lite) but they don't have double eyelets
and sockets, which is not quite as desirable. Another suitable rim
would likely be the Rigida Sphinx, also unavailable in 700C in the US.
You will find instead Mavic touring rims that have the right basic
specs, but they are expensive and I believe Mr Cholina has a low
opinion of them. Velocity rims also have a good reputation but are also
single eyeletted and I don't know the models.
You and your builder were fooled by Mavic into thinking the rim was
strong because of the 36 holes and the aero profile. An aero profile
makes for a stiff rim, but the strength to weight ratio is not as good
as a box section with double eyelets. People confuse stiffness with
strength and durability. They are not the same, the classic extreme
example being styrofoam. Now that we have an "exploded view" of the
innards of the CXP33, thanks to you, we can see that in fact it is not
a strong rim, the walls, from your photograph, appearing to be
extremely thin. They have to be, to get a 460g rim in that cross
section. Compare the cross sections at
<www.ambrosiospa.com/cerchi_corsa.htm>, and you will see that their
comparable model, the Balance, is 500g, and it already has much thinner
walls than the 460g Excellence or the 480g Evolution, in turn both
thicker than the 430g Excellight. Probably the Evolution with 32mm
tires at 90 psi would work for you, without a heavy load, but you
should check with Chalo to be sure.
I certainly would not use your wheels at your weight, even if the tire
size and pressure were within spec. I suggest returning the wheels to
the builder or selling them on eBay. One would expect them to be fine
only for someone much lighter.
As for the heavier Ambrosio touring rims, the strongest, according to
the weight and the fact that it is a box section with double eyelets
and sockets, would be the C.C. 28. You can see from the cross section
that it has very thick walls, and the weight is correspondingly high. I
doubt you really need this strong a rim, unless you are touring with a
heavy load. I haven't used it or the Keba, but the Keba is similar to
the model no longer available I do use from a different manufacturer, a
smaller and lighter (~560g) 622-17. But I weigh much less than you.
On this forum Jobst has described some terrible accidents, one where
the rider went backwards onto a rear wheel. It's not something you want
to do. I think you are fortunate to have escaped disastrous injury. The
wheels you have are evidently not suitable for you and you need to find
something better, or else start planning your funeral.
carl...@comcast.net
wrote:
Dear Greg,
Well, that raises a few questions . . .
How much short of 275 lbs?
Tires as fat as 37mm on a rim with an apparent interior diameter of
14mm? Or only the 35 and 32mm models that most posters have mentioned?
Pressures as high as 80-85 psi ("estimated" by thumb tests, which
leaves even higher pressures quite possible)?
The CXP33 has apparent exterior/interior widths of 19.4/14 mm, judging
by this cross-section:
http://www.lickbike.com/productpage.aspx?PART_NUM_SUB='2104-28'
Any idea what those dimensions are on an MA2? I won't be surprised if
the two rims are similar, but those first 3 questions are probably
more important.
Cheers,
Carl Fogel
G.T.
50.
>
> Tires as fat as 37mm on a rim with an apparent interior diameter of
> 14mm? Or only the 35 and 32mm models that most posters have mentioned?
55mm mtn bike tires.
>
> Pressures as high as 80-85 psi ("estimated" by thumb tests, which
> leaves even higher pressures quite possible)?
No, up to 70 psi with a gauge.
>
> The CXP33 has apparent exterior/interior widths of 19.4/14 mm, judging
> by this cross-section:
>
> http://www.lickbike.com/productpage.aspx?PART_NUM_SUB='2104-28'
>
> Any idea what those dimensions are on an MA2? I won't be surprised if
> the two rims are similar, but those first 3 questions are probably
> more important.
>
Don't know. And I don't recall seeing tables with max pressure per tire
width for the MA-2.
serv...@df.unipi.it
41 wrote:
>ss
> section. Compare the cross sections at
> <www.ambrosiospa.com/cerchi_corsa.htm>, and you will see that their
> comparable model, the Balance, is 500g, and it already has much thinner
> walls than the 460g Excellence or the 480g Evolution, in turn both
> thicker than the 430g Excellight.
Has anyone ever given a thought that a rim is under very severe stress
upon braking, which does not necessarily go with the rider's weight,
and that a thin wall and a non-boxed geometry are really bad features
in that regard?
Sergio
Pisa
nikojorj_ja...@yahoo.fr
41 wrote:
> 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/m
> 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)
That shows it : the 37mm@85psi configuration puts (a tad) less stress
on the rim walls than a Mavic-acceptable (and quite common)
23mm@138psi.
So, this configuration alone cannot be a single cause for the failure,
but the high-side load generated may be a contributive factor.
On the other hand, rider weight can also be a factor according to
Mavic's documentation. I can not find it again on Mavic's website, but
I found the following downloaded 2-3 years ago (original in french, I
tried to translate) :
"Mavic recommends that the total weight of the biker and his gear does
not exceeds the following :
- Road rims : 100 kg (except MA3 : 85 kg) ;
- MTB rims :
- 75 kg on X517 ;
- 90 kg on X139, X139 Disc, X221, X223 Disc, X225, X 317 Disc,
X618, X3.1 and X3.1 Disc ;
- 115 kg on F219 Disc, F519, D521, D321 Disc and D3.1 Disc.
- Asphalt [touring] rims : 105 kg on T223 and T224, 125 kg on T520."
So the 275lb rider (that makes around 125kg or am I wrong?) could only
use the T520 rim in the Mavic Range.... and taking into account the
bike weight, he should go elsewhere.
It was definitively written as a recommendation, not a warranty limit,
but according to that data any Mavic road rim should not be used with a
total weight of more than 220lb, ie a rider weight of more than
190-200lb, with the exception of MA3 rim limited at 185/160lb.
Imho, the main factor of the catastrophic failure could well be a
pre-existing defect, either a manufacturing one or a previous
unremarked shock, with the higher-than-recommended load as a
contributing factor.
> I suggest the rider needs a 500+ g rim,
Sounds very sensible according to the above.
serv...@df.unipi.it
nikojorj_ja...@yahoo.Fr wrote:
>
> That shows it : the 37mm@85psi configuration puts (a tad) less stress
> on the rim walls than a Mavic-acceptable (and quite common)
> 23mm@138psi.
That's exactly what I thought, without looking at any specs in fact (if
you can, read my post on it in it.sport.cuclismo).
The stress on the rim from the inflated tube depends on the inflation
pressure and the width of the bed onto which the tube pushes. It has
nothing to do with how large the tube and tire are outside of the rim.
At least, this is what makes sense to me.
Sergio
Pisa
Earl Bollinger
news:1149619643....@c74g2000cwc.googlegroups.com...
> 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 thought about it some more, and I think that since it was mentioned that
the tube had a inner tear hole from where it blew out at.
That either you have a rim strip that wasn't protecting the tube from the
spoke holes as expected, or the tire slipped off the rim at one point
causing the tube to fail, and then the sudden release of air pressure
coupled with a maybe overtensioned wheel, along with the rider's weight and
power pedaling along, made the wheel taco. At that point pedaling along
under power the wheel jammed in the frame or brakes and had the total
failure collapse like you show in the pictures.
I suspect one culprit is the use of narrow road bike rims with big wide
tires, the tire sides are at a angle and maybe don't get hooked well, plus
the tube doesn't get down into the tire rim area very well and maybe doesn't
put enough pressure on the tire bead to help lock it in place.
Thus wider rims and making sure the rim tape is wide and good for the rim
would seem to me to be the solution to preventing this from happening again.
you...@cox.net
Earl Bollinger wrote:
> I thought about it some more, and I think that since it was mentioned that
> the tube had a inner tear hole from where it blew out at.
> That either you have a rim strip that wasn't protecting the tube from the
> spoke holes as expected, or the tire slipped off the rim at one point
> causing the tube to fail, and then the sudden release of air pressure
> coupled with a maybe overtensioned wheel, along with the rider's weight and
> power pedaling along, made the wheel taco. At that point pedaling along
> under power the wheel jammed in the frame or brakes and had the total
> failure collapse like you show in the pictures.
> I suspect one culprit is the use of narrow road bike rims with big wide
> tires, the tire sides are at a angle and maybe don't get hooked well, plus
> the tube doesn't get down into the tire rim area very well and maybe doesn't
> put enough pressure on the tire bead to help lock it in place.
> Thus wider rims and making sure the rim tape is wide and good for the rim
> would seem to me to be the solution to preventing this from happening again.
Hi Earl!
I disagree with you on all counts. The rim strip was intact and showed
no signs of spoke-head puncture. If the bead coming off the rim had
been the cause of tube failure, the tube's rip would have been on the
SIDE of the tube (by the bead) rather than against the rim strip (where
it actually was). The rim tape WAS wide enough to completely cover the
inside of the rim. I agree with the LBS's diagnosis - the rim failure
was the cause of the tube failure - not vice versa. This means that
either a defective rim OR a rim with excessively thin walls was the
original cause of the failure. I'm shipping the wheel, rim-strip,
tube, and tire back to the wheelbuilder for analysis and inspection.
He'll report back after his investigation.
I appreciate your feedback, but I think that your conjectures (although
perfectly reasonable) do not apply in this case.
Peter Cole
>
> Imho, the main factor of the catastrophic failure could well be a
> pre-existing defect, either a manufacturing one or a previous
> unremarked shock, with the higher-than-recommended load as a
> contributing factor.
>
>
>> I suggest the rider needs a 500+ g rim,
>
> Sounds very sensible according to the above.
>
I weigh 230. My strategy has always been to (where possible) use
components rated for heavy duty, like touring stuff for road bikes and
DH stuff for off-road. I think it makes sense to spec bike weight as a
fraction of rider weight, and that goes double for wheels, which are
often the most problematic component for heavy riders.
I mostly use Mavic touring rims on my road bikes, just to manage my own
weight. I have used lighter rims, but only in a box section. I have used
those lighter rims with over-size tires (35mm studs), but I inflate them
only to 65psi. I inspect rims regularly, measure sidewall wear, and am
conservative about retiring them.
Heavy riders should stay away from lightweight components, a rider
that's 50% heavier than nominal should be using a rim that's much
heavier than nominal -- it's that simple.
41
nikojorj_ja...@yahoo.Fr wrote:
> 41 wrote:
> > 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/m
> > 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)
By the way, sorry, make those kiloNewtons.
> That shows it : the 37mm@85psi configuration puts (a tad) less stress
> on the rim walls than a Mavic-acceptable (and quite common)
> 23mm@138psi.
> So, this configuration alone cannot be a single cause for the failure,
> but the high-side load generated may be a contributive factor.
I note that the 55/70psi used by another poster here gives 13.3 kN on
an MA2, same interior width (13.5mm) as the CXP33. I believe this shows
just how much stronger the MA2 is.
> On the other hand, rider weight can also be a factor according to
> Mavic's documentation. I can not find it again on Mavic's website, but
> I found the following downloaded 2-3 years ago (original in french, I
> tried to translate) :
>
> "Mavic recommends that the total weight of the biker and his gear does
> not exceeds the following :
> - Road rims : 100 kg (except MA3 : 85 kg) ;
> - MTB rims :
> - 75 kg on X517 ;
> - 90 kg on X139, X139 Disc, X221, X223 Disc, X225, X 317 Disc,
> X618, X3.1 and X3.1 Disc ;
> - 115 kg on F219 Disc, F519, D521, D321 Disc and D3.1 Disc.
> - Asphalt [touring] rims : 105 kg on T223 and T224, 125 kg on T520."
>
> So the 275lb rider (that makes around 125kg or am I wrong?) could only
> use the T520 rim in the Mavic Range.... and taking into account the
> bike weight, he should go elsewhere.
I agree with this. While 37/85 is not a good combination with this rim,
it does not seem to be the only factor, the rider's 275lb weight being
even worse. Still, I would like to know why the plot above does not
give a horizontal line for Mavic's specs. Perhaps only the 25 and 28
specs are ideal, and for the rest they give a further safety factor.
This makes sense according to the tire/rim compatibility charts,
although I don't have time to check them right now.
Thus apart from any tire/rim incompatibility, the rim itself is clearly
way too underbuilt for the rider's weight. There may or may not also
have been a manufacturing defect, but there does not seem to be any
necessity for that.
> > I suggest the rider needs a 500+ g rim,
>
> Sounds very sensible according to the above.
Problem may be finding a good one, especially if the rider doesn't want
to go the 600+g route. The Ambrosio Evolution, box section at 480g,
with 32mm tires, might be a bare safe minimum, but here someone of that
size should speak up and let us know. The concept of "bare safe
minimum" is a little unclear anyway.
e
41
serv...@df.unipi.it wrote:
> nikojorj_ja...@yahoo.Fr wrote:
> >
> > That shows it : the 37mm@85psi configuration puts (a tad) less stress
> > on the rim walls than a Mavic-acceptable (and quite common)
> > 23mm@138psi.
>
> That's exactly what I thought, without looking at any specs in fact (if
> you can, read my post on it in it.sport.cuclismo).
> The stress on the rim from the inflated tube depends on the inflation
> pressure and the width of the bed onto which the tube pushes. It has
>
> At least, this is what makes sense to me.
Correct, but there is also force in the other direction, on the
hooks/wall, which depends on the product of inflation pressure and tire
cross sectional radius.
Pat Lamb
> Add a rider who weighs twice as much as you do, and 500 miles later
> the rim fails dramatically, just as expected.
>
> Darned few riders weighing 265 lbs are likely to be putting 37mm tires
> at 80-85 psi on such a narrow rim. The ones who do are going to find
> out the hard way that it's a very bad idea.
>
> The posters who are surprised are generally riding 35mm or smaller
> tires (that 2mmm matters), using 75% or less as much pressure (20 to
> 40 psi makes a big difference down that low), and don't weigh 265 lbs
> (60 to 130 pounds less is a considerable change).
Carl,
You've posted about the rider's weight several times in this thread, and
I don't understand the attention you're giving his weight. Why do you
think the rider weight is so important? ISTM rider weight won't change
the tube pressure or hoop stress significantly.
Pat
serv...@df.unipi.it
> Correct, but there is also force in the other direction, on the
> hooks/wall, which depends on the product of inflation pressure and tire
> cross sectional radius.
I beg to differ, here.
Strictly speaking there is a continuum of angles, and trigonometric
factors, involved; the result of all being just the (weighted)
vectorial sum. There is no way any such contribution can depend on
anything but the inside pressure, no matter what the shape of the other
portions of the tube are, which does depend on the size of the
clincher.
So, what ultimately matters is only the shape of the rim, to which that
portion of the tube conforms, and the inflation pressure.
Sergio
Pisa
G.T.
Damn, I have to get down to 90kg.
jason...@gmail.com
41 wrote:
<snip>
> Still, I would like to know why the plot above does not
> give a horizontal line for Mavic's specs. Perhaps only the 25 and 28
> specs are ideal, and for the rest they give a further safety factor.
> This makes sense according to the tire/rim compatibility charts,
> although I don't have time to check them right now.
One factor no one has mentioned (at least not that I noticed) is that
the hoop stress we've calculated acts tangentially to the tire casing.
At the bead/rim interface, the diameter of the tire changes the
tangential direction substantially. For a given rim width (let's use
the Mavic rim in question) a 19mm tire's casing exerts force nearly
radially where it touches the rim. A 37mm tire exerts its force both
radially and axially (that is, in a direction parallel to the hub
axle). This axial force stresses the bead flange in bending. Of course,
the 19mm tire produces bending stresses in the rim's bead flange as
well, but those stresses are not nearly as high.
One data point:
I remember when Bontrager first re-sized MA40s and MA-2s...they were
shockingly light for mountain bike rims. People ran 2.2-inch tires on
those rims at maybe 55 psi. Trek briefly used their Matrix ISO-C
extrusion (a road aero rim) to make mountain bike rims. (This was prior
to Trek's purchase of Bontrager). That rim was quite narrow, and I had
a friend who ran 2.2-inch Gary Fisher tires (the plain square-block
ones) on those rims, and while they looked absurd on such narrow rims,
they worked fairly well for him. In retrospect it strikes me funny that
back in the day my friend was riding Bontrager-inspired Trek rims with
Fisher tires (on a Fisher Hoo Koo E Koo bike), and just a few years
later all three brands would be melded into a single entity. I guess it
shows how much the industry has consolidated.
At any rate, I'm not trying to suggest that tire width is irrelevant
because my skinny friend rode fat tires on skinny rims fifteen years
ago. I think tire width does matter, but so do a lot of other factors.
As much as I love computing stresses, I don't think that's the whole
story here. People have advanced all sorts of ornate theories about
this failure, but it's hard to know anything without a phyisical
inspection (and the photomicrographs that would result). It's certainly
an interesting topic for discussion, however.
Cheers,
Jason
carl...@comcast.net
Dear Pat,
No, the rider weight shouldn't change air pressure or the force that
the air pressure exerts on the side of the rim.
But the rider's weight constantly flexes the rim as it rolls under the
hub. In this case, when the spokes under the hub lose about 150 pounds
of tension, it's because that rim section is being pressed toward the
hub with 150 pounds of force. This force is exterted through the tire
sidewalls, which act partly like a wedge--some of the force goes to
spreading the rim.
With the pre-stressed aluminum rim, the flexing is invisible to the
naked eye, but the results in this case are not.
The heavier the rider, the greater the flexing, the sooner things
break.
Here's an imaginary metal bridge resembling the short section of rim
at the contact patch--which will break it sooner, a 180 pound weight
added and removed once per second, or a 275 pound weight added and
removed once per second?
Consider two more points.
Much heavier rims are routinely recommended for tandems that carry
about 275~350 pound loads. (Compare a truck rim to a car rim.)
The same rim with the same tire at the same inflation spinning in a
truing stand is unlikely to fail before the next ice age--no
fluctuation in stress in the rim.
But this rim failed in 500 miles, about 30 hours at 15~20 mph and
about 375,000 revolutions at about 750 revs per mile. Sounds like a
fatigue failure.
Cheers,
Carl Fogel
carl...@comcast.net
Dear Sergio,
The frictional force retarding the spin is applied by rubber brake
pads, which should fail long before the aluminum rim--the rim sidewall
is coming at the pads lengthwise, giving it enormous strength that
way.
As for the pinching force at right angles, the rim is supported by
about 100 psi of air pressure--you have to squeeze that much just to
overcome the static pre-tension of the inner tube pushing the rim
outward.
Cheers,
Carl Fogel
Chalo
>
> Hi! I'm the clydesdale whose Mavic blew up, instigating this thread.
> I'm planning on having all my wheels rebuilt with different rims (I'm
> scared of those Mavics now...). I'm not familiar with Ambrosio rims.
> I note that Ambrosio offers multiple "touring" rims with wider
> profiles. What differences are there between the different Ambrosio
> touring rims, and which is the strongest?
In your situation, I'd try Alex Adventurers. They are just about the
stoutest 700c rims of normal width that I've ever had the opportunity
to build, and they feature unusually thick sidewalls. The DM18 is also
a good strong and well-proven rim. The G2000 and G6000 look like good
candidates for heavy-duty road bike use, though I've not had the chance
to try those.
Alex rims are made with stronger metal (6061-T6) than most of the
offerings from better-known manufacturers. Their quality control is
generally more consistent than I have come to expect from the pricier
makers, and they are available in a larger variety at the heavy end of
the range.
Chalo Colina
carl...@comcast.net
[snip]
>Alex rims are made with stronger metal (6061-T6) than most of the
>offerings from better-known manufacturers.
[snip]
>Chalo Colina
Dear Chalo,
When I was testing spoke-squeezing spoke-tension increase, one comment
about the low results was that my rim must be "cheesy."
It looked like an ordinary, inexpensive 32-spoke box-section rim with
eyelets and inserts from Performance.
The label says "6061-HT6 aluminum."
What are most of the offerings from better-known manufacturers made
of?
Cheers,
Carl Fogel
Chalo
>
> Chalo wrote:
>
> >Alex rims are made with stronger metal (6061-T6) than most of the
> >offerings from better-known manufacturers.
>
> about the low results was that my rim must be "cheesy."
>
> It looked like an ordinary, inexpensive 32-spoke box-section rim with
> eyelets and inserts from Performance.
>
> The label says "6061-HT6 aluminum."
>
> What are most of the offerings from better-known manufacturers made
> of?
Most Mavic rims and all Velocity rims are made from 6106 aluminum (a
softer alloy than the industrially common 6061) to allow better control
of surface finish, and thus prettier extrusions. I understand that the
properties of 6106 are similar to 6063, another weak, but easily
extruded, corrosion resistant aluminum that finds ubiquitous use in
architectural elements such as window frames, screen doors, and the
like. Material property data for 6106 aluminum are difficult to come
by. There is some mention of the alloy in this document:
http://www.capral.com.au/product_info/aluminium.pdf
Araya (in the past) and Odyssey (currently) have used 7000-series
alloys, presumably of higher strength than 6061, in a few of their rim
offerings. Mavic boast of some higher strength code-named alloy which
they use in the Open Pro, but this could be ordinary 6061 given that
their other rims are made of cheese.
Chalo Colina
carl...@comcast.net
Dear Chalo,
Here's another link to the same site--you pick the 6xxx alloy on the
upper right.
The 6106 starts out about 87~80% as strong as the 6061, but there's an
odd weakening as the 6106 gets thicker:
UTS(MPa)
| YS(MPa)
| | Elongation(%)
| | |
6061 T6 260 240 8 (any thickness)
6106 T6 235 210 8 (up to 10mm thick)
205 170 8 (>10-25mm thick)
185 160 10 (>25mm thick)
http://www.comalco.com/freedom.aspx?pid=525
Any idea why 6106 gets weaker as it gets thicker?
Cheers,
Carl Fogel
Chalo
Solution heat treatment depends on being able to quickly cool the
material to "freeze" the alloying elements in their diffused state.
This is typically accomplished by water quenching.
Some alloys are more sensitive to cooling rate than others-- for
instance, 7005 alloy is common in bicycles because its rate of air
cooling in bicycle-type thicknesses after welding results in a fairly
decent heat treatment. It looks like 6106 must chill rapidly during
heat treatment to attain its best strength. But the maximum thickness
of a bicycle rim extrusion will be nowhere near 10mm, and thus it
should display strength properties at the upper range of what is
indicated in the table.
Chalo Colina
Barnard Frederick
> Why? If the Mavics have quality control problems, isn't it possible
> definitively establish that excess tire width was the root-cause of
> this wheel failure, I'd be happy to continue using the Mavics with tire
> sizes recommended by Mavic. Unfortunately, I don't think that has been
> established (nor do I think it can be). I'm left with wheels that I
> can't trust. So let's cut to the chase - why do you think my decision
> to replace the Mavic rims is dumb and wasteful? Thanks!
Dewd, you were using a tire three sizes too large for the rim, and you
are a major Clydesdale. There certainly isn't a quality control problem
with the dope you are smoking. Yes, get some proper touring rims. Your
size and the size of the tire you want to use makes it a no-brainer.
What's next, a thread complaining about the early bearing failure of
your titanium spindle BB?
41
The poster is referring to clincher tires, not tubular. The tube pushes
down on the rim bed as you describe, but the beads pull up and out on
the hooks of the rim as well. The tire casing above the rim and its
width play the role of the rim bed and its width as you describe. Just
view what you described upside down, sort of.
G.T.
> you...@cox.net says...
>
>
>>Why? If the Mavics have quality control problems, isn't it possible
>>that the remaining rims could likely fail also? If I could
>>definitively establish that excess tire width was the root-cause of
>>this wheel failure, I'd be happy to continue using the Mavics with tire
>>sizes recommended by Mavic. Unfortunately, I don't think that has been
>>established (nor do I think it can be). I'm left with wheels that I
>>can't trust. So let's cut to the chase - why do you think my decision
>>to replace the Mavic rims is dumb and wasteful? Thanks!
>
>
> Dewd, you were using a tire three sizes too large for the rim, and you
> are a major Clydesdale. There certainly isn't a quality control problem
> with the dope you are smoking.
My MA-2s never broke, ever, even abusing them with really fat tires at
higher pressures. And I've split 2 x517s down the middle using right
sized tires at low pressure, and I've had spokes pull through x618s.
Yeah, Mavic's quality control is still the same as it was 20 years ago.
Werehatrack
>
>dnvr...@aol.com wrote:
>> How many of you would put an identical wheel/tire/pressure in as a
>> replacement and continue riding?
>
>Let me change that a bit.
>
>A quote from the person for whom the wheel failed:
>
>"The bike is now in the shop for inspection & repair. The dead wheel is
>packed for return to Rev. Chuck who will do some in-depth analysis of
>the failure. I've closely inspected the remaining three wheels built
>with identical components - none show signs of cracking or distress. I
>guess I'll be using the remaining wheels unless there's a good reason
>not to? "
>
>Your reaction to that statement?
In the case of a product with a long track record of trouble-free
service, where a specific failure is generally believed to have been
due to a random unusual fault, I don't see anything illogical about
it. OTOH, if it was me, I'd be watching those other wheels closely
for the first sign of a crack from a spoke hole. I don't believe that
the crack which I suspect precipitated the failure was so sudden in
its development that it couldn't have been spotted by a quick pre-ride
inspection, but at 500 miles since new, I doubt that anyone would have
anticipated that such an inspection was needed.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
Werehatrack
>On 7 Jun 2006 12:07:36 -0700, dnv...@aol.com wrote:
>
>>
>>carlfo...@comcast.net wrote:
>>> On 7 Jun 2006 08:08:23 -0700, dnv...@aol.com wrote:
>>>
>>> >How many of you would put an identical wheel/tire/pressure in as a
>>> >replacement and continue riding?
>>>
>>> Dear D.,
>>>
>>> I wouldn't put a 37mm tire on a rim recommended for no more than 28mm
>>> and 117 psi and then blow it up to an estimated 80-85 psi,
>>> particularly if I weighed 275 lbs.
>>>
>>> I've heard of a case where the wheel failed catastrophically within
>>> 500 miles on smooth pavement when this was done.
>>>
>>> Cheers,
>>>
>>> Carl Fogel
>>
>>How about a 28mm tire?
>
>Dear D.,
>
>I'd happily put a 28mm tire on a rim rated for that width with no more
>than 117 psi--and inflate it to about 100 psi or less. A recommended
>maximum is a warning, not an invitation to see what happens.
>
>In any case, the destroyed rim was wearing a 37mm tire inflated to an
>estimated 80-85 psi when it abruptly tore itself in half after only
>500 miles.
>
>That 37mm is 32% beyond the CXP33's maximum recommended width.
>
>What could be a more impressive and dramatic illustration that Mavic
>was right about those rim limits? Or that wider tires exert more
>leverage on rims?
If your logic is valid, then there are (and have long been) a lot of
riders out there on time bombs, and we should have been seeing a lot
more reports of such failures. I really think this was just what it
appears to be; a random defect failure. The fact that it failed in
500 miles while the other three identical wheels remain sound is
strong evidence that it's not the choice of tire and inflation which
was seminal, though the rider's weight may have a bearing. And in
point of fact, I've seen lots of oversize tires used on lightweight
rims at moderate overpressure (for the tire, the rim, or both) for
longer periods without failures. There has to be a margin of safety
in the design of such things because the maker know that there will be
instances when the limits will be exceeded for good reason, bad
reason, or lack of reason. While exceeding the published specs is not
a good idea, it's common, and seldom has such spectacular results in
such a short time. Perhaps that rim might have gone farther under a
lighter rider; I suspect, however, that it was just a unit that was
going to fail, and the rider's weight may have sped it along somewhat.
Mavic makes *lots* of rims. It's hardly surprising that failures
occur from time to time, and if you're making lots of rims, your name
will come up in such failures quite often. On the other hand, they're
far from the only large rim producer, but yet their name seems to pop
up more often than any other when rim failures are under discussion.
Given that some shortcomings in their products have been identified in
the past, I think there may be reason to be wary of using their rims
in high-stress applications. I'm beginning to think that they're just
engineering their products too close to the limits in general.
carl...@comcast.net
Dear Werehatrack,
A rider puts a 37mm tire on a rim whose manufacturer recommends it for
no more than a 28mm tire, about 32% beyond the manufacturer's chart
for that rim.
An independent site about tandems and heavily laden touring bikes
warns that the tire is a couple of sizes out into the daner zone for a
rim with such narrow internal dimensions.
The rider inflates it to a "thumb-test" 80-85 psi, which looks to be
about 30%-40% beyond the maximum that the manufacturer would recommend
for such a tire on that rim if the manufacturer recommended it, which
the manufacturer doesn't. (If the rider's thumb was off 10%, the tire
could have been at 95 psi.)
The rider weighs around 270 pounds.
After only 500 miles, the rim fails catastrophically.
Gosh, who could have predicted this?
Lots of other heavy riders put wider-than-recommended tires on their
rims and pump them up--well, maybe not quite that heavy, that wide, or
that high.
I have a vision of a lot of people standing at the edge of a frozen
pond.
They're staring at a hole beyond a "Danger Thin Ice" sign.
Some of them are saying that the fellow on the pogo-stick who just
vanished is entitled to sue someone.
Others are explaining that all the other people skating a little past
the sign prove that it should have been safe to pogo-stick much
further out there.
Cheers,
Carl Fogel
41
Werehatrack wrote:
> appears to be; a random defect failure. The fact that it failed in
> 500 miles while the other three identical wheels remain sound is
> strong evidenc e that it's not the choice of tire and inflation which
> was seminal, though the rider's weight may have a bearing.
Hold on- although the original poster was not clear on this, the
implication seems to have been that those other wheels were not yet in
service.
Look at the wall thickness of that rim as revealed in the "exploded
view", and look at e.g. the cross section of the corresponding Ambrosio
Balance, which, even at 40g heavier, also has much thinner walls than
the lighter Ambrosio box section rims. Forget the tire cross sections,
that is a weak rim, and the rider weighs 275lbs.
> longer periods without failures. There has to be a margin of safety
I believe the rider to be about 90lbs over that, not even taking into
account the tire cross section.
ç
41
you...@cox.net wrote:
> 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.a mbrosiospa.com/touring.htm>).
>
> Hi! I'm the clydesdale whose Mavic blew up, instigating this thread.
> I'm planning on having all my wheels rebuilt with different rims (I'm
> scared of those Mavics now...). I'm not familiar with Ambrosio rims.
> I note that Ambrosio offers multiple "touring" rims with wider
> profiles. What differences are there between the different Ambrosio
> touring rims, and which is the strongest?
I see Ambrosio has made some changes for 2006:
<www.ambrosiospa.com/2006-8.HTM>
Gone are the Excellence and Excellight, the Keba and the CC28. The
Evolution has been redesigned to be a little wider (14mm vs 13.5), and
with a slightly more aero profile (i.e. like that of the Keba instead
of a box section). The weight has been maintained, so that means the
walls are thinner, as evident from the sections. Not a good
development.
They also have a new model, the Excursion. At 510g it should have been
ideal. But they gave it a semi-aero profile too, with very heavy brake
tracks, and the walls of the top half of the rim are therefore thinner
than they were in the Evolution. Not sure what the overall result will
be. Fashion, fashion, fashion.
carl...@comcast.net
Dear 41,
Hold on . . .
Utterly off topic, but thanks for teaching me something.
I could have sworn that I've seen that hold-on phrase used many times
by someone else on RBT and decided that it was a sign that something
arrogant or evasive was about to appear.
But you used someone else's "hold on" phrase to introduce a perfectly
reasonable, inoffensive post about the topic.
(Hell, your post is nicer than this post.)
I'm gonna watch you more closely and see if I can pick up more tricks
like this.
Back on topic, I missed any links in the thread to the Ambrosio, so
here's a CXP33 cross-section:
http://www.lickbike.com/productpage.aspx?PART_NUM_SUB='2104-28'
And here's an Ambrosio Balance cross-section:
It's scarcely any wider than the CXP33 on the crucial inner width that
determines the leverage of any oversized tire's sidewalls. I suspect
that this is more important than the thickness or bracing, but you may
have a point about really thin rim sidewalls.
Here's an Ambrosio box-section rim for comparison:
If you want to look at other Ambrosio rim cross-sections, this page
has lots of nice Ambrosio cross-section links with thumbnails:
http://www.yatego.com/radsport-rennrad/felgen/30-35-13,3,,1,3
Cheers,
Carl Fogel
carl...@comcast.net
Dear 41,
I think that you're right about the slight changes in width and
weight, but the increased width between rim sidewalls may strengthen
the rim more than the decreased weight.
"May" should be emphasized.
In any case, the rim-well width should vary less than the thickness of
any rim members. The rim is extruded like toothpaste from a die, which
wears and creates increasingly thicker and heavier rims--up to about
10%, according to posts that educated me a few years about this
annoying variation.
Here's the weight weenies rim page, which lists some claimed and
measured weights for Ambrosio, with the usual caveats about possible
model changes confusing things:
http://weightweenies.starbike.com/listings/components.php?type=rims
The single Ambrosio Balance was 512 grams, a little bit over its
claimed 500 gram weight.
The single Mavic cxp33 was 455 grams, a little bit under its claimed
470 grams.
The single MA2 (27" tubular from 1995) was 420 grams, with no known
claimed weight.
A quick glance shows an obese Mavic T217 D that claimed only 470 grams
on its driver's license, but was an embarrassing 13% heavier (532
grams) when forced to stand on the hay scales.
An Ambrosio Crono was even worse--claiming only 280 grams and weighing
25% more at 350 grams.
Overweight rims are marked with red % figures.
The worst anorexic (green % figures) was much less dishonest--a ZIPP
280 told its doctor that it weighed 284 grams, but got down to 269
grams, 5.28% underweight, by sticking its finger down its throat at
the foundry.
Cheers,
Carl Fogel
you...@cox.net
RS wrote:
> I would value Jobst's or Sheldon's thoughts on this wheel failure.
Sheldon B. e-mailed me personally. He thought it was either spoke
overtension or a defect in the rim. Since spoke overtension is
confidently eliminated (the other three wheels from the same
wheelbuilder had spoke tension checked at the LBS & all were consistent
& reasonable), we are left with a defective Mavic. The wheelbuilder is
going to analyze the failed rim, and I've sent him the wheel, tube,
tire, and rim-strip.
Since my remaining three wheels use the same Mavic model (CXP33), I'm
having all wheels rebuilt with different (and wider, and heavier) rims
from Ambrosio (the "Keba").
Next question - does Mavic owe me anything? Since Sheldon says
"defect," it would seem reasonable to ask for a new rim pair? Sheldon
mentioned NOTHING about contributory negligence from tire width,
inflation pressure, or rider weight - maybe he thought these were
non-issues or maybe he just didn't take the time to comment...
Thanks!
Capt...@sheldonbrown.com
> Sheldon B. e-mailed me personally.
Right, personally.
This is a very long thread, which I have not read, just glanced at the
photos and the first couple of postings. I gave you a quick opinion:
"My guess is either a defective rim or grossly overtensioned spokes."
You were running an excessively wide tire at excessive pressure, this
might have been a contributing factor. If I could examine the rim I
might have a firmer opinion on this point. If that were the cause, I
would expect to see a section of the rim splayed outward.
However, I have not seen the rim, and did not feel confident that I
know enough about the case to comment publicly, that's why I replied
privately and have not participated in this thread.
>He thought it was either spoke
> overtension or a defect in the rim. Since spoke overtension is
> confidently eliminated (the other three wheels from the same
> wheelbuilder had spoke tension checked at the LBS & all were consistent
> & reasonable), we are left with a defective Mavic. The wheelbuilder is
> going to analyze the failed rim, and I've sent him the wheel, tube,
> tire, and rim-strip.
>
> Since my remaining three wheels use the same Mavic model (CXP33), I'm
> having all wheels rebuilt with different (and wider, and heavier) rims
> from Ambrosio (the "Keba").
I advised the him against against this:
"That's silly, Mavic rims are generally excellent. Every brand has an
occasional defective unit though."
> Next question - does Mavic owe me anything? Since Sheldon says
> "defect,"
Actually what I said was:
"My guess is either a defective rim or grossly overtensioned spokes."
Please note the word "guess." I am not asserting that this was
necessarily the case.
> it would seem reasonable to ask for a new rim pair?
Not if you use my casual "guess" as an "authority."
> Sheldon
> mentioned NOTHING about contributory negligence from tire width,
> inflation pressure, or rider weight - maybe he thought these were
> non-issues or maybe he just didn't take the time to comment...
Right. I could see that this was a huge thread, one that I didn't have
time to read. The photos didn't give me sufficient information, so
without actually seeing/feeling/measuring the rim I was not prepared of
offer a "professional opinion."
Sheldon "Strictly Speaking, Possibly" Brown
+--------------------------------------------+
| If it can't be expressed in figures, |
| it is not science; it is opinion. |
| --Robert A. Heinlein |
+--------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
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