mollusk

The final location of the tire is interesting since it is no longer above the brake pads. I'm guessing that during the failure the rim with tire still attached was pulled down through the brake pads and later the rim (without tire) sprung back to the brake pad area or the tire itself was pulled through. Just a wild guess, but are there any rubs, dents, or marks on the underside of the chain stay? Perhaps the tire blew off and became tangled in the spokes, hit the chain stay giving a sudden vertical impulse (as felt by the rider), and also causing considerable damage to the wheel.

Rev.Chuck

I built this wheel and three otherss for FH. It was built up to Mavics spec for tension using a Park tensionmeter to measure. I have had some of the Reflex tubular rims crack even when tensioned per Mavic, so I was pretty careful not to get these to the high side as FH is pretty big and the spokes are DT Alpines.

Oz, the spokes do not have eyelets but they do have an insert to spread the load.

AndrewP

The close-up pictures of the fractures show the sleeves around the nipple heads that interconnect the inner and outer walls.

John E

As an engineer, I have the same erudite, highly technical comment.

Seriously, I have NEVER seen a rim failure like yours, although 30 years ago I did hear of a Fiamme yellow breaking at the weld. (For the record, in 100k miles / 160k km of road cycling, I have broken 3 left cranks (Sugino Mighty Compe aluminum at the pedal eye, Campagnolo Veloce aluminum at the spindle eye, Agrati steel at the cotter/spindle eye), 2 rear axles (one solid, one QR, both 5-speed), 2 or 3 frames (Nishiki Competition at the BB shell, Peugeot UO-8 between the right chainstay's clearance dimples, plus my first 1960 Capo, which had been restraightened after a crash), 1 front hub flange (Shimano high-flange, 36 hole 3X), and 1 pedal (SunTour aluminum platform).)

I am glad it wasn't your FRONT wheel!

waterrockets 

Wow, that's a lot of scary failures. I've ridden about 140K miles, on and off-road. I've broken, well, let's see, a chain and a couple spokes. I keep all my bikes for 10 years+, so I'm not using new stuff all the time, though it is new when purchased...

Regarding the wheel, I've never seen anything like that. It doesn't look like an overtenioning issue, or the rim would have tacoed or spokes woud be ripped out of the rim. It must be a rim problem.

That's a CXP-33 or CXP-22, right?

I'm loving my 36H Velocity Deep-Vs about now...

ozbiker

Certainly looks to me like there is NO build problem. When I got back into riding after 14yrs off the bike I weighed 115kg (253lb). The old Mavic 193 back wheel took exception to this and grew longitudinal cracks from the spoke holes. I've ridden about 6000km (3700mi) over the past 7 months which trimmed off LOTSA weight, but also made the cracks grow longer until I was finally too uncomfortable with them to continue riding. I have just laced up my old hubs into a pair of used MA40 rims and the result looks good and rides very smoothly. Time will tell how well they last, but I expect the lower body weight will get a longer wheel life.
It seems to me from personal experience and from talking to club members that if you are heavy you will get shorter wheel life - aluminium will always fail by fatigue caused by cyclic loading, eventually. Check your wheels often and monitor crack growth.

Rev.Chuck

It is a CXP 33. And it was picked over the Deep V because of the inserts, my reccomendation. I have asked Glenn to ship me everything so I can deal with Mavic and I will rebuild it however he wants.
The only thng I have ever seen near this, has been crashed wheels and GEL 280s.
I have had issues with big guys cracking Reflex rims but just small cracks around the eyes and only after a couple of thousand miles.

ozbiker

Oh!! I see, you are right. I thought they were plastic inserts to plug the spoke holes.

jordanb

I really like the suggestion that you take it to a metalluraligist. It'd probably be the only way to figure out what happened (sheer stress, fatigue, etc). If it's fatigue that really says something about aluminum!

slvoid

Fatigue would not cause something like that break. You'll need to view the area of shear under high magnification to see what happened, maybe you can take some close up pics for us.

My only guess is that you had something real sharp like a piece of glass embedded on the right side of your rear brake pad that scored a deep but short groove in your rim before the piece of glass broke off. Everytime you braked, it would compress the section of the wheel behind the brake, causing it to bulge outwards every time. Eventually... WHAMO.

Blue Order

Here's an article on Brake Pad Rim Wear

slvoid

He's only had the wheel for 500 miles. I suspect it's not so much long term wear as something gouging a giant scratch in the braking surface.

NoRacer

If that is a Mavic CXP33, then the widest tire to be placed on that rim, according to Mavic, should be 28mm @ 117 psi max. OP, did you say that you had a 37mm wide tire on that rim? I see that WTB has the Slickasaurus in 28mm, 35mm, and 37mm widths.

Bobby Lex

It was the shooter on the grassy knoll!

Honestly, I'd swear you hit something really big and immovable to cause that kind of damage. I just can't imagine that you were just rolling along and your rim exploded like that without some external force causing it.

Go have a talk with your "custom" builder.

Bob

waterrockets 

This may be on the right track.

I had an ancient MTB rim that was run with old brake pads for a little too long, so the braking surface was weakened (which I didn't know at the time). I moved the wheel to my kid/trailer/trail-a-bike hauling rig, and put slicks on it at much higher pressure.

On the first ride, the rim walls separated at the seam and released the tire, so the tube exploded. The rim was bent blown out about 1/4 inch right at the seam.

I think tire pressure over a larger area could be to blame here. It's not the same failure mode as mine, but the tire overpowered the rim, which sounds similar.

seeker333

I had a velocity synergy 559 rim blowout a piece of the sidewall ~ 3 inches long after the tube exploded. It had been inflated to 65-70psi. It did this parked in the garage at night. I had 5,000 miles on the rim, tube and tire combo at the time.

So your blowout is by no means unprecedented.

One side of your rim looks to me like it could be caused by a blowout. The other side looks like it was folded in two by either spoke tension and/or your weight while riding.

Stuff happens pretty fast in those situations, tough to explain with high confidence.

CRUM

In my experience, rim failure due to brake wear is different than this failure. Rims failing from brake wear tend to fail along a parallel line with the circle of the rim. The bead just folds over at the weak section.

alanbikehouston

If the rim was designed for a 28mm tire, and the fork and the chain stays of that bike were designed (as many bikes are these days) for a 23mm to 25mm tire, putting a 37mm tire on that bike might leave very little clearance between the tire and the side of the fork and the chain stays.

If the tire was a tight fit to the fork or chain stays, a stick, stone, or bit of road debris could wedge between the tire and the fork or chainstays, causing the wheel to lock-up. At that point, the speed of the front wheel would most often just kick the debris loose. But, if the debris is solid, such as a stone, it could wedge tightly. At that moment, something must give way. If the stone is wedged against the fork, a carbon fork will give way. If the stone is wedged against the chainstays and the tire, the rim could give way, as the rim is likely to be less weaker than the chain stay.

Before assuming that Mavic is at fault, some other questions should be clearly answered:

- what size tires were the fork and chain stays designed for?

- what are the size of tires that the factory shipped this bike with?

- what size tires did Mavic suggest be used with this particular rim?

- what PSI level did Mavic suggest for the actual size of tire mounted on the rim?

- what weight of rider does Mavic suggest is suited for this particular rim?

- what was the actual size of the tire mounted at the time of the failure, the actual PSI at the time of the failure, and the weight of the rider at the time of the failure?

Many problems with bikes (not all) involve not reading, understanding, and following the manufacturer's guidelines. For example, bikes with carbon seat tubes come with instructions that the seat clamp be tightened only with a torque wrench, and only to specified torque levels. The number of owners who tighten their seat clamps with a torque wrench? Somewhere very close to zero.

will dehne

FH:
You know that we are all celebrating that you did not get hurt.

Here is what I would do:
Go to Mavic and tell them that such a failure is NOT acceptable. Demand that they make an INDEPENDENT laboratory analysis to be given to you. If they do not do that, tell them that you will do it and will go after them for consequential damages.
Suggest they got lucky that you did not get hurt and they should investigate and come up with a solution so this does not happen again.
In defense of Mavic: They may determine that your weight was excessive or that you have the wrong tires on these wheels. If that is the case, OK, lesson learned.
I would have a lawyer advising me but not confront Mavic yet with that lawyer.

I have experience with such things in my Automation business. This is the procedure we follow, always.

NoRacer

I'm sure that both Mavic and WTB lawyers would say, "Go pound sand!", because design specs for both the wheel and the tire where exceeded. Just because it's common practice to use a butter knife for a screwdriver doesn't mean that you should, nor would the manufacturer of the butter knife replace it because you bent the tip using it as a screwdriver.

BostonFixed

Better yet, let the person who built you these wheels deal with all that bs for you. Mavic, your wheelbuilder should be bending over backwards for you...

Rev.Chuck

He is sendiing me the wheel. I am not to optimistic about help from Mavic, they are unresponsive even with the MP3 program. If the hub is undamaged, I will build a new wheel with a different rim.

BostonFixed

That sucks that mavic is unresponsive...makes you wonder exactly how much they value their products if they don't back them up..

2manybikes

Was anything done to the wheel recently? Was it just trued or adjusted in any way?
Did the LBS or you do anything at all to your bike just recently?

Did you recently change a flat?

DnvrFox

I have forwared this link to rec.bicycles.tech

Hopefully, Jobst Brandt might see it.

I am sure he would be interested and would offer some insights.

If any thoughts come up, and you aren's subscribed to rec.bicycles.tech, I will paste in here.