# Pics of Millar's exploding wheel(s)?



## cyclelogic72 (Dec 1, 2006)

I didn't catch the TV coverage of stage 19 and ha've looked to the obvious sources for pics (cyclingnews, pez,etc.) but have come up dry. Anyone have a link to a pic or video of Millar's/Mavic's very, very bad day on Stage 19?


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## cadence90 (Sep 12, 2004)

.....








.


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## Len J (Jan 28, 2004)

cyclelogic72 said:


> I didn't catch the TV coverage of stage 19 and ha've looked to the obvious sources for pics (cyclingnews, pez,etc.) but have come up dry. Anyone have a link to a pic or video of Millar's/Mavic's very, very bad day on Stage 19?


Here you go.

Len


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## cyclelogic72 (Dec 1, 2006)

Thanks.


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## stevesbike (Jun 3, 2002)

that's incredible. I've riden Ksyriums as training wheels for a long time and they are bulletproof. Can't believe Mavic let those past quality control (looks like a design flaw). If that were one of the top 3 GC guys their tour would have been done right there.


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## zosocane (Aug 29, 2004)

stevesbike said:


> Can't believe Mavic let those past quality control (looks like a design flaw). If that were one of the top 3 GC guys their tour would have been done right there.


I had the same thought re Mavic. I have their Cosmic Carbone Premiums and two pairs of Kysrium SLs -- never had a single problem with any of them. Yesterday was not a good day for Mavic.


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## culdeus (May 5, 2005)

What happened? I never saw it and that photo doesn't exactly make it any more clear? How does a tire just come off the rim like that? I'm lost.


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## cadence90 (Sep 12, 2004)

culdeus said:


> What happened? I never saw it and that photo doesn't exactly make it any more clear? How does a tire just come off the rim like that? I'm lost.


Not the tire off the rim; the alloy rim (with the tire still on it) came off the carbon wheel. 

He powered down the ramp and the thing just blew apart. He switched bikes (he's already grabbing his bottle in the photo) and had another problem one minute later. Tough luck. Really bad day.

Maybe the wheels needed sun protection more than he did....


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## culdeus (May 5, 2005)

cadence90 said:


> Not the tire off the rim; the alloy rim off the carbon wheel.
> 
> He powered down the ramp and thing just blew apart. He switched bikes (he's already grabbing his bottle in the photo) and had another problem one minute later. Tough luck. Really bad day.
> 
> Maybe it was the wheels that needed sun protection more than him.


Yeah, but those are just the stock carbon wheels that mavic sells right? Surely he warmed up on that bike and rode it around. How does that just happen right then and there?

And that's a big amount of connecting material to just evaporate instantaneously. Though I've never really even seen a disc rim up close so I'm not sure how it all comes together.


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## cadence90 (Sep 12, 2004)

culdeus said:


> Yeah, but those are just the stock carbon wheels that mavic sells right? Surely he warmed up on that bike and rode it around. How does that just happen right then and there?
> 
> And that's a big amount of connecting material to just evaporate instantaneously. Though I've never really even seen a disc rim up close so I'm not sure how it all comes together.


Apparently they are not stock Cometes, but may be converted track wheels. 
The alu rim separated from the carbon fairing, I suppose as a result of the intense torque he applied going down the start ramp.
I don't know why: bad glue, bad rim, bad luck....


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## shabbasuraj (May 14, 2005)

I really need/wish to see a video of this.


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## cadence90 (Sep 12, 2004)

shabbasuraj said:


> I really need/wish to see a video of this.


I haven't found any video yet. The wheel just exploded.

http://www.velonews.com/tour2007/news/articles/12995.0.html

Britain's David Millar managed to contain his anger after the wheels literally came off his bid for a top finish in the final Tour de France time trial on Saturday. 

The 30-year-old, who rides for Saunier Duval, finished the 55.5km race against the clock from Cognac to Angouleme well outside the top 10 after a pair of disastrous mechanicals cost him crucial time. 

Millar initially blamed wheel producers Mavic, but later admitted he could not put his finger on exactly why the incidents happened. 

"I've got no idea (why it happened)," he said. "The Mavic disc exploded in the first 500 meters. The rim came off the carbon, they gave me my spare bike, I went off, but after 300 meters that one went as well!


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## El Caballito (Oct 31, 2004)

cadence90 said:


> Maybe the wheels needed sun protection more than he did....


That's pretty funny! I guess he didn't apply sunblock to his wheel.
Good one...:thumbsup:


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## JaeP (Mar 12, 2002)

*Mavic ZAP*

This isn't the first time Mavic had bad publicity in the Tour. A long time ago I remember seeing Charlie Mottet (Team RMO) bombing down a mountain. He had a problem with the new Mavic electronic ZAP shifting system. It must've shorted because the rear dereailleur was jerking violently. Of course the motorcycle camera man zoomed in as close as he could so that my TV screen was filled with a Mavic rear derailleur having epiliptic siezures.


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## EasyRider47 (Sep 18, 2005)

*Additional Possibility....?*

My first thoughts when I heard about the "exploding" wheels:

First wheel - technical issues, design/maintenance issue.

Second wheel - 2 wheels in less than 500 yards - this may be well beyond technical issues.....hmmmm....sabotage....?


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## turbogrover (Jan 1, 2006)

EasyRider47 said:


> Second wheel - 2 wheels in less than 500 yards - this may be well beyond technical issues.....hmmmm....sabotage....?


Hehehe! Yeah, where was Lance when all of this happened??


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## wasfast (Feb 3, 2004)

There was a tech article in one of the Pro Cycling mags in the last couple months that detailed his TT rig. The rear wheel is a Comete track disc that was converted for road use. Can't comment on why it self destructed though.....


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## gizzard (Oct 5, 2005)

JaeP said:


> This isn't the first time Mavic had bad publicity in the Tour. A long time ago I remember seeing Charlie Mottet (Team RMO) bombing down a mountain. He had a problem with the new Mavic electronic ZAP shifting system. It must've shorted because the rear dereailleur was jerking violently. Of course the motorcycle camera man zoomed in as close as he could so that my TV screen was filled with a Mavic rear derailleur having epiliptic siezures.


Really? I remember Mottet very well but don't remember him ever riding Mavic's ill-fated ZAP system. I remember Boardman and Simon Lessing dabbling with ZAP but not Mottet.


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## PJay (May 28, 2004)

*was the wheel on PEDs?*

was the wheel on PEDs?

hey, i'm just sayin'

when a wheel performs that good, you have to suspect drugs.


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## tkavan01 (Jun 24, 2004)

PJay said:


> was the wheel on PEDs?
> 
> hey, i'm just sayin'
> 
> when a wheel performs that good, you have to suspect drugs.



as far as i've ever heard it's never tested positive,

back on topic, it defn seems like a failure of the bonding agent, maybe the team stored the wheels improperly, or maybe they went through a temperature cycle that broke the bond apart? would make sense since both wheels where transported together...

you would think someone would have ridden the bike around the parking lot and maybe the problem would have shown up... what wheel did he put on after the second failure?


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## JohnnyTooBad (Apr 5, 2004)

I heard the 2nd failure was a broken chain, not another exploding wheel.

Eh???


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## weltyed (Feb 6, 2004)

im with tkavan on this one. my guess is the wheels were stored improperly and the bonding agent gave. heat, humidity, cold in a plane storage area. who knows?

maybe he didnt notice anything before because the torque applied in the TT was much more violent than that on a trainer or ride up to teh starting ramp.

as far as the chain, paul and phil originally reported that the first wheel met its demise because his chain broke and that blew the wheel, i guess by slapping it? on sundays coverage they corrected that.

and i have to hand it to millar for coming out against mavic. yeah, it could have been stored improperly, but still...
the article stated he initially finger mavic, then later backed off and said he wasnt sure he could pinpoint the genisis of the problem. he then goes on to say "the MAVIC disk wheel exploded..." sounds like someone freaked and told him he couldnt blame Mavic becaus ethey are sponsor. he then makes sure everyone knows its a Mavic wheel.


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## rule (Dec 2, 2004)

:yesnod:


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## il sogno (Jul 15, 2002)

culdeus said:


> Yeah, but those are just the stock carbon wheels that mavic sells right? Surely he warmed up on that bike and rode it around. How does that just happen right then and there?


Most teams warm up with a regular (spoked) rear wheel on the trainer so as not to wear the tire down.


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## jbierling (Mar 30, 2006)

EasyRider47 said:


> hmmmm....sabotage....?


Same thought I had.

-Joel


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## jhbeeton (Dec 8, 2004)

*Failure mechanism*

First off ... the photo doesn't represent an exploded wheel ... yes the tire & apparent extrusion have separated from the disc but that is hardly an explosion.

Second, if you think of a standard spoked wheel. The torsion of the gears on the hub body transmit the force through the flange which then loads up the spokes in tension. The top half of the wheel effectively supports the weight loaded on the axle ( spokes in tension). The the tension in the spokes also transmits the rotation to the rim/tire. Clincher tires don't require glue as the pressure ( 8-10BAR) of the tube on the inner casing ( Relatively small area) is sufficient to keep the rim & tire from slipping against one another.

I would have imagined that the failure was going to happen at the hub shell which has a significantly smaller diameter and corresponding interface with the disc material.

I'm not going to claim to be a finite element analysis guy, but that's what my gut's telling me.

The shear forces don't seam to make sense at the rim extrusion b.c I've managed to finish rides on tubulars with little or no tacky glue left after a roadside change and you'd think that just a reasonable amount of riding would shear the tube & stem off the rim.

This also begs the question: why's Millar riding clinchers?


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## Spunout (Aug 12, 2002)

He is not riding clinchers, that is the Mavic disc design: Aluminum extruded rim with two carbon disks glued together. 

Glue problem.


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## TurboTurtle (Feb 4, 2004)

jhbeeton said:


> First off ... the photo doesn't represent an exploded wheel ... yes the tire & apparent extrusion have separated from the disc but that is hardly an explosion.
> 
> Second, if you think of a standard spoked wheel. The torsion of the gears on the hub body transmit the force through the flange which then loads up the spokes in tension. The top half of the wheel effectively supports the weight loaded on the axle ( spokes in tension). The the tension in the spokes also transmits the rotation to the rim/tire. Clincher tires don't require glue as the pressure ( 8-10BAR) of the tube on the inner casing ( Relatively small area) is sufficient to keep the rim & tire from slipping against one another.
> 
> ...


"The [spokes in the] top half of the wheel effectively supports the weight." False. As long as the bottom spokes are still in tension (as they should be) the wheel 'stands' on bottom few. - TF


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## bonkmiester (Sep 23, 2005)

Spunout said:


> He is not riding clinchers, that is the Mavic disc design: Aluminum extruded rim with two carbon disks glued together.
> 
> * Glue problem*.


.....


...yup...

...bad adhesive mix and/or bad mating surfaces prep...

....you have to etch metals when bonding to carbon fibre/epoxy matrix...it gives some "tooth" to the metal, and cleans it of contaminates [oils]...

...monolithic disc/rim is best, bond the halves [r/l] togeather when they are still "green"...


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## epic (Apr 16, 2005)

I was wondering what kind of dropouts his TT bike has. I pictured the wheel getting pulled sideways into the chainstay as he accelerated and then the aluminum rim being knocked off of the carbon wheel.


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## phill_rotorman (Aug 20, 2007)

TurboTurtle said:


> "The [spokes in the] top half of the wheel effectively supports the weight." False. As long as the bottom spokes are still in tension (as they should be) the wheel 'stands' on bottom few. - TF


TT, am I missing out on something? 

A wheel is a tensile construction, not a compression construction. Remove the top spokes and a wheel collapses. Remove the bottom ones and it stands (albeit with deformation, the lower spokes do keep it in shape)

/edit/
aah, you're talking about the disk wheel. ok.


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## TurboTurtle (Feb 4, 2004)

phill_rotorman said:


> TT, am I missing out on something?
> 
> A wheel is a tensile construction, not a compression construction. Remove the top spokes and a wheel collapses. Remove the bottom ones and it stands (albeit with deformation, the lower spokes do keep it in shape)
> 
> ...


No, I'm talking about spoked wheels.  If you get on the bike and measure the change in tension you will find that the top spokes do not increase - only the bottom spokes decrease. The hub is not hanging from the top.

"Remove the top spokes and a wheel collapses. Remove the bottom ones and it stands..."

Remember I said only as long as the bottom spokes remain in tension as designed.

TF


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## phill_rotorman (Aug 20, 2007)

TurboTurtle said:


> No, I'm talking about spoked wheels. If you get on the bike and measure the change in tension you will find that the top spokes do not increase - only the bottom spokes decrease. The hub is not hanging from the top.
> 
> "Remove the top spokes and a wheel collapses. Remove the bottom ones and it stands..."
> 
> ...


Seriously, a spoked wheel is a tensile construction. Spokes are not columns (look at engineering column calculators and buckling calculators and the answer is obvious) There is no way that a few flimsy spokes could take the compressive forces of supporting a cyclist - especially on rough terrain! You must have a measuring error there. 

To test your theory, take a wheel and remove just over half the spokes. If the lower half really does hold the hub up, that would mean that if you load the hub with all spokes supporting it from below, the hub will stay put if you load it. It won't. It'll sag, and the lower spokes will jump out of their seats. When you load it hard, the side spokes will eventually take up the weight, and the rim will ovalize.

Additionally, look at strait-pull spoke construction wheels. The tension of the spoke keeps the spoke in it's housing in the hub. There is no obstacle stopping it from backing out, in fact, if you unscrew the nipple you'll be able to push the spoke out of its seat in the hub with barley any force. This type of construction wouldn't work if a wheel was a compression construction!

Each and every spoke above the height of the axle is taking part of the strain. Each and every spoke below the axle is only loaded enough to keep the rim from buckling. The drop in tension is because the lower spokes are released from tension from the rider's weight, and then the tension drops more from a minute deformation of the rim when the tire below it contacts the road.


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## Fredke (Dec 10, 2004)

TurboTurtle said:


> "The [spokes in the] top half of the wheel effectively supports the weight." False. As long as the bottom spokes are still in tension (as they should be) the wheel 'stands' on bottom few. - TF


Draw a free-body diagram of forces on the hub. All of the upward force is coming from the top spokes. The bottom spokes are in tension = pulling down. There's no way to support an object against gravity by pulling down on it.


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## TurboTurtle (Feb 4, 2004)

phill_rotorman said:


> Seriously, a spoked wheel is a tensile construction. Spokes are not columns (look at engineering column calculators and buckling calculators and the answer is obvious) There is no way that a few flimsy spokes could take the compressive forces of supporting a cyclist - especially on rough terrain! You must have a measuring error there.
> 
> To test your theory, take a wheel and remove just over half the spokes. If the lower half really does hold the hub up, that would mean that if you load the hub with all spokes supporting it from below, the hub will stay put if you load it. It won't. It'll sag, and the lower spokes will jump out of their seats. When you load it hard, the side spokes will eventually take up the weight, and the rim will ovalize.
> 
> ...


Sorry, but you aren't getting the pre-stressed engineering here. THE SPOKES HAVE TO BE UNDER TENSION. The 'removing half the spokes', etc. experiments are irrelevant.

I suggest reading Part 1 of Brandt's "the Bicycle Wheel". "Many people believe that it is self-evident that the hub hangs from the upper spokes...This type of misconception is similar to the belief...that the sun rotates around the earth." There's more; get the book.

TF


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## TurboTurtle (Feb 4, 2004)

Fredke said:


> Draw a free-body diagram of forces on the hub. All of the upward force is coming from the top spokes. The bottom spokes are in tension = pulling down. There's no way to support an object against gravity by pulling down on it.


Copied from my reply above:
------------
Sorry, but you aren't getting the pre-stressed engineering here. THE SPOKES HAVE TO BE UNDER TENSION. The 'removing half the spokes', etc. experiments are irrelevant.

I suggest reading Part 1 of Brandt's "the Bicycle Wheel". "Many people believe that it is self-evident that the hub hangs from the upper spokes...This type of misconception is similar to the belief...that the sun rotates around the earth." There's more; get the book.

TF
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## Guest (Aug 20, 2007)

TF is right. The rim stays round under load due to the essentially equal centripetal forces (tension) provided by the spokes distributed within the rim. End of story.

The actual physics gets pretty complicated when looking at things from a dynamic situation (once you have velocity, or worse still acceleration, horizontally to the hub) - so lets not go there.


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## hppy4u (Sep 15, 2002)

Looks like Mavic has apologized for Millar's debacled ride. Seems like it was a special prototype wheel that was lighter than the usual comete. Attached below is sourced from Cyclingnews:

Mavic comments on Millar wheel failure
Stage 19 was not meant to be for David Millar 
Photo ©: Cyclingnews.com 
David Millar (Saunier Duval-Prodir) had a disastrous ride during Stage 19 of this year's Tour de France. Almost immediately after catapulting himself down the start ramp, Millar's disc wheel failed catastrophically, but thankfully, the Saunier Duval-Prodir team mechanic was at the ready with a spare bike. Unfortunately, though, that machine suffered the same fate just a few meters up the road, laying waste to Millar's aspiration for a TdF stage win on a course that suited him nearly perfectly. 

Millar was using a prototype Carbon Comete rear disc wheel from team sponsor Mavic. As compared to the existing Comete, this new model was said to be substantially lighter, at least partially due to the use of a lighter aluminum rim extrusion. Upon further examination of the race footage, it became obvious that Millar's wheel failure came about as a result of a complete separation of that bonded rim section from the disc on both occasions. 

Sean Sullivan, Marketing Director for Mavic Inc., confirmed the failure mode. "David was using a prototype Carbon Comete [that was] much different and lighter than a regular stock version. I'm told the extrusion totally separated from the carbon flanges of the disc wall. At this time it hasn't been determined exactly why it happened, but it was some sort of failure of the bond between the surface of the aluminum extrusion and the inside of the carbon flange."

"While a lightweight prototype, I don't think the occurrence was necessarily from any new technologies that were used," continued Sullivan. "It just appears to be more of a freak isolated incident with the preparation of the surfaces or the bonding process on his particular wheel and not a common failure with our competition prototypes or our production Cometes. Mavic prides itself on the quality and durability of our products and while we like to push the limits of technology for our racers' benefit, we would never put any racer on a wheel that we thought might have a catastrophic failure of this nature and it's horrible that it happened."

Mavic apparently places at least some blame on the initial shock from the starting ramp, but that does little to explain the second failure. According to Sullivan, "This incident happened right out of the start gate after the slight impact from hitting the pavement off the start ramp, which then uncovered the flaw in the bond in this particular wheel. David rode the same wheel with no problems in the Prologue. It's terribly unfortunate for David to have this happen during such a critical stage of the Tour on a day where he was sure to do very well."


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## Fredke (Dec 10, 2004)

TurboTurtle said:


> Sorry, but you aren't getting the pre-stressed engineering here. THE SPOKES HAVE TO BE UNDER TENSION. The 'removing half the spokes', etc. experiments are irrelevant.


I understand that the spokes have to be under tension, but the bottom spokes' tension is still pulling DOWN and the top spokes' tension is still pulling UP. I don't understand why you say that the downward force is what supports the hub, not the upward force of the top spokes.

Let's reduce things to the case of two spokes at 180 opposition. The bottom one has tension T, which exerts a force T downward on the hub. Let's say the load on the hub from the weight of the bike is W. The top spoke must have tension (T+W) to balance things.

Now in the free-body diagram we'd draw the hub with gravity pushing down with force W, the bottom spoke pulling down with T, and the top spoke pulling up with (T+W).

I just don't get what you mean when you say that the downward force of T (the spoke's tension) is what's supporting the hub and that the upward force (T+W) is not supporting it. I'm not saying that you're wrong, but I really don't get what you mean.


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## TurboTurtle (Feb 4, 2004)

Fredke said:


> I understand that the spokes have to be under tension, but the bottom spokes' tension is still pulling DOWN and the top spokes' tension is still pulling UP. I don't understand why you say that the downward force is what supports the hub, not the upward force of the top spokes.
> 
> Let's reduce things to the case of two spokes at 180 opposition. The bottom one has tension T, which exerts a force T downward on the hub. Let's say the load on the hub from the weight of the bike is W. The top spoke must have tension (T+W) to balance things.
> 
> ...


To start let’s take the wheel with the bottom half of the spokes removed. The hub is hanging from the top spokes. Hop on the bike. Does the wheel hang from the top spokes? Hell no, the rim collapses. The rim cannot transfer the forces to the top, so what does? Nothing. In this ‘hanging’ model the wheel would collapse.

Now look at a wooden wagon wheel. Downward force on the hub (at the center, not the top) countered by an equal upward force from the ground. Again, the rim cannot hold the wagon up. What holds it up is the compression of the bottom spokes. The rim deforms at the bottom and the bottom spokes get shorter. There is nothing happening at the top.

Now look at the bike wheel. Again, AS LONG AS ALL SPOKES REMAIN UNDER TENSION, we have a downward force at the hub, upward force from the ground, the rim deforms at the bottom, the bottom spokes get shorter and there is nothing happening at the top.

Positive compression (wagon wheel) and negative tension (bike wheel) are the same thing to the tensioned spoke. 

TF


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## Guest (Aug 21, 2007)

Ok, basic stuff. For a wheel to work it must stay round. The wheel is the case of a bike is the rim (plus it's support structure). By design, rim deflection under static load is very small (otherwise the rolling resistance would high, for example). The collective forces (centripetally towards the hub) on the rim due to all the spokes is sufficient to make the rim *very* rigid. 

You can't just do a horizontal or vertical summation of forces to get your answer. A bike wheel is a ridgid body, who's strength is determined by the summation of many force vectors at various angles relative to the rim, flanges and hub centerline.

If you want to make this hard, then you are going to have to do a fair bit of math to show how a wheel works. But really, it's so simple...."A caveman could do it" :thumbsup:


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## Guest (Aug 21, 2007)

For those who really want to understand: http://www.amazon.com/Bicycle-Wheel-3rd-Jobst-Brandt/dp/0960723668


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## TurboTurtle (Feb 4, 2004)

AJL said:


> For those who really want to understand: http://www.amazon.com/Bicycle-Wheel-3rd-Jobst-Brandt/dp/0960723668


You just recommended a book that contradicts what (I think) you said. - TF


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## Fredke (Dec 10, 2004)

So if I follow you, if you progressively load the bicycle with more and more weight, the wheel holds together nicely until the moment that the tension on the very bottom spoke becomes zero and at that moment there's nothing to support the hub so the wheel folds up. Is that correct?


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## bonkmiester (Sep 23, 2005)

bonkmiester said:


> .....
> 
> 
> ...yup...
> ...


update:

from Tech Talk on Velo news 8/21...link here

Mavic: ... "It just appears to be more of a freak isolated incident with the preparation of the surfaces or the bonding process on his particular wheel"...


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## Guest (Aug 21, 2007)

TurboTurtle said:


> You just recommended a book that contradicts what (I think) you said. - TF


Really? Well, I've heard good things about the author and have read a couple of reviews of the book, figured it would explain things well. Oops :blush2:


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## Guest (Aug 21, 2007)

Fredke said:


> So if I follow you, if you progressively load the bicycle with more and more weight, the wheel holds together nicely until the moment that the tension on the very bottom spoke becomes zero and at that moment there's nothing to support the hub so the wheel folds up. Is that correct?


If you are responding to me, then no. The point is that it's not about one spoke.


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## Fredke (Dec 10, 2004)

AJL said:


> If you are responding to me, then no. The point is that it's not about one spoke.


No, I was responding to TurboTurtle. I agree with you that the net force is the vector sum of all the spokes. I am questioning TurboTurtle's assertion that the only forces that "support" the hub due to downward tension from the lower spokes and his implication that the moment the lower spokes are de-tensioned the whole wheel will collapse.


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## TurboTurtle (Feb 4, 2004)

Fredke said:


> So if I follow you, if you progressively load the bicycle with more and more weight, the wheel holds together nicely until the moment that the tension on the very bottom spoke becomes zero and at that moment there's nothing to support the hub so the wheel folds up. Is that correct?


No, did not say or mean that. The load on a conventional (i.e. 32h) wheel is supported by several spokes at the bottom. First the botton one loses tension and the load is transfered out even further. Then the ones next to it lose tension, etc. At some point the rim will no longer have the strength to tranfer that force outward and it will collapse. Note that, even as it collapses, the top spokes are still fine. If it was hanging, the top ones would have to break before the wheel would collapse, right? - TF


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## TurboTurtle (Feb 4, 2004)

AJL said:


> Really? Well, I've heard good things about the author and have read a couple of reviews of the book, figured it would explain things well. Oops :blush2:


It does explain things quite well. - TF


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## Guest (Aug 21, 2007)

TurboTurtle said:


> It does explain things quite well. - TF


Well, of course the author wouldn't look at the wheel as a rigid body. I didn't want to complicate things by noting that, like most light weight structures, a bicycle wheel is approaching a rigid body form while lowering the weight. But, in doing so I missed went off track a bit from the debate.

In any case, looking at a static load failure: if the force on the hub is increased, at some point that force exceeds the verticle component of centripetal force exerted by the spokes and the load limit of the rim itself - leading to a collapse of the wheel. It's a bit more complicated than that, since we are actually dealing with torque and moments. But, as an approximation for a static load - your explaination works fine.

That's what I get for having a degree in physics - I complicate stuff :blush2:


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## TurboTurtle (Feb 4, 2004)

AJL said:


> Well, of course the author wouldn't look at the wheel as a rigid body. I didn't want to complicate things by noting that, like most light weight structures, a bicycle wheel is approaching a rigid body form while lowering the weight. But, in doing so I missed went off track a bit from the debate.
> 
> In any case, looking at a static load failure: if the force on the hub is increased, at some point that force exceeds the verticle component of centripetal force exerted by the spokes and the load limit of the rim itself - leading to a collapse of the wheel. It's a bit more complicated than that, since we are actually dealing with torque and moments. But, as an approximation for a static load - your explaination works fine.
> 
> That's what I get for having a degree in physics - I complicate stuff :blush2:


So then would you agree that it (in laymen's terms) 'stands' on the bottom spokes? - TF

btw - I am only talking static.

EDIT: A physics joke. You wake up in an undergrad lab and have to figure out which lab you are in before you get asked a question. If the experiment moves, its BIO. If the experiment stinks, it's CHEM. If the experiment doesn't work, it PHYS. - TF


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## Guest (Aug 22, 2007)

TurboTurtle said:


> So then would you agree that it (in laymen's terms) 'stands' on the bottom spokes? - TF


Actually, it stands on the rim - like any wheel would. I mean, in a suspension bridge, you are riding on the road, not the cables, even though the cables are holding the road up. So while you are correct in a way, it sort of like pretending there isn't a wheel. Does that make sense?

PS Good joke, though I'd prefer something like "if you are glowing, it PHYS" :wink:


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## TurboTurtle (Feb 4, 2004)

AJL said:


> Actually, it stands on the rim - like any wheel would. I mean, in a suspension bridge, you are riding on the road, not the cables, even though the cables are holding the road up. So while you are correct in a way, it sort of like pretending there isn't a wheel. Does that make sense?
> 
> PS Good joke, though I'd prefer something like "if you are glowing, it PHYS" :wink:


Think I should start another thread explaining that a tire is not held up by the air, but 'stands' on it's tensioned sidewalls? - TF


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## Guest (Aug 22, 2007)

TurboTurtle said:


> Think I should start another thread explaining that a tire is not held up by the air, but 'stands' on it's tensioned sidewalls? - TF


LOLZ! Maybe we are just twisted up by terminology, but I wouldn't be comfortable saying that something is "standing" on a support member that is in tension. The tension is maintaining the integrity of the wheel by preserving the 'roundness' of the rim. That's the bottom line for me.


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## QBNastyNaS (Dec 19, 2007)

http://www.youtube.com/watch?v=daTQb6tsz6M&feature=related there you got it guys


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