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  1. #51
    feros ferio John E's Avatar
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    Thanks, Denver. I, too, would be interested to hear what Jobst has to say about this.

    I concur with the others that this is NOT a rim sidewall erosion issue.

    This story reminds me of one of our early 1970s Bikecology customers. This teenager, who weighed about 250lbs / 115kg, promptly pretzled the OEM Rigida steel rim on his new Peugeot UO-8. To prevent recurrence, I rebuilt the rear wheel with 14 ga. spokes and a steel Schwinn rim.
    "Early to bed, early to rise. Work like hell, and advertise." -- George Stahlman
    Capo [dschaw'-poe]: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger, S/N 42624
    Peugeot: 1970 UO-8, S/N 0010468
    Bianchi: 1981 Campione d'Italia, S/N 1.M9914
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  2. #52
    feros ferio John E's Avatar
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    Thanks, Denver. I, too, would be interested to hear what Jobst has to say about this.

    I concur with the others that this is NOT a rim sidewall erosion issue.

    This story reminds me of one of our early 1970s Bikecology customers. This teenager, who weighed about 250lbs / 115kg, promptly pretzled the OEM Rigida steel rim on his new Peugeot UO-8. To prevent recurrence, I rebuilt the rear wheel with 14 ga. spokes and a steel Schwinn rim.
    "Early to bed, early to rise. Work like hell, and advertise." -- George Stahlman
    Capo [dschaw'-poe]: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger, S/N 42624
    Peugeot: 1970 UO-8, S/N 0010468
    Bianchi: 1981 Campione d'Italia, S/N 1.M9914
    Schwinn: 1988 Project KOM-10, S/N F804069

  3. #53
    Email for new group DnvrFox's Avatar
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    Gone - email me at dnvrfox@aol.com for new group of old 50+ folks

  4. #54
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    My guess is initial separation of the tire from the rim, due either to being oversize for the rim or possibly some other defect that would cause the tire to lift and make contact with the frame. The wheel had by this event lost its "roundness". This was rapidly followed by a braking obstruction due to interference between the tire and the frame, likely at the brake caliper/ seatstay bridge. (Was this the point where the rider was pitched upward?) Traction on the lower rim from the spokes along the inferior half of the locked wheel was met by a compression of the rim along the top half of the wheel by the forward rotation of the wheel, creating a shearing force to the rim at about the 8:30/2:30 meridian. The front part of the rim fractured first. The shearing force continued rearward but slightly weakened and caused a slower tear-like break of the rim at the 2:30 clock position.

  5. #55
    Senior Member Old Hammer Boy's Avatar
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    Lucky it was the back wheel. Can you imagine such a failure at 19 MPH on a front wheel?

  6. #56
    Junior Member KurskKnyaz's Avatar
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    Hey, where did you get that guard for your front charing. I am removing the lower 2 charings (because they are usless for road biking) and want something to keep my chain from falling off and rubbing off my pants.

  7. #57
    Senior Curmudgeon
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    Quote Originally Posted by alanbikehouston
    ...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?
    Hi AlanbikeHouston!

    To answer your questions (and they're good ones, for the most part):

    The Klein Navigator is a touring frame, and the fork/chain stays were designed for 37mm tires plus fenders if wanted. My 37mm tires had good clearance both front and rear.

    Since I didn't buy this bike as a finished product, I can't say what tires originally shipped. I bought the frame and built it up myself.

    Mavic recommends anywhere from 19 to 28 mm tires for these CXP33 rims.

    Mavic's PSI recommendations were only for their recommended sizes, and the ultimate PSI declined with increasing tire size. Their widest recommended tire (28mm) was 117 PSI (max.) according to Mavic.

    Mavic does NOT specify any weight limit for this rim (nor any other Mavic rim that I'm aware of).

    The actual pressure at time of failure I estimate to be 80 psig. My weight is 275.

  8. #58
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    In the other thread on this rim failure, there is a photo of the Mavic specs chart for the CPX33 that lists it as designed for tires that are 19mm to 23mm wide. The tire mounted on it was a size 37mm.

    The other thread also included a note from Sheldon Brown on the possible consequence of putting a too wide tire on a too narrow rim: the failure of the rim.

    If in fact a 37mm tire was place on a rim made for tires in the 19mm to 23mm range, the rim was 50% narrower than recommended.

    And, the owner weighs about twice as much as the typical rider for whom a 19mm to 23mm tire is designed: the riders of the pro peloton, and the guys who imitate the guys in the pro peloton.

    Because the bike was designed for wide tires, it would make sense to rebuild that wheel using rims that are much wider. And, given the rider's weight, it ought to be the heaviest, strongest rim in that size. Perhaps even a rim that is designed for use with a tandem bike.

    The industry "hypes" equipment that is "super-aero" and "super-light" becauses that is what the 150 pound riders in the pro peloton use. But, most of us weigh far more, and none of us are racing for money. So, we need the sturdiest, safest gear we can find, even if that results in a heavier bike.
    Last edited by alanbikehouston; 06-06-06 at 06:43 PM.

  9. #59
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    Quote Originally Posted by alanbikehouston
    ...the Mavic specs chart for the CPX33 that lists it as designed for tires that are 19mm to 23mm wide...
    Quit repeating this erroneous information. MAVIC SPECS THIS CXP33 RIM FOR UP TO 28MM TIRES!

    Here is the link to Mavic's chart:

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

    The reason Rev. Chuck and I selected this rim originally was for its 36-spokes, strong-V-profile, and nipple ferrules. This was the heaviest-duty rim we could find. This rim is NOT a "lightweight." Don't fault our choices saying we were trying for light weight at the expense of durability - it isn't so.

  10. #60
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    Quote Originally Posted by ozbiker

    [snip]

    The top spokes are already loaded at this time by the weight of the rider - remember, the bike hangs off the top spokes.

    [snip]

    JohnF
    Dear John,

    You'd think that a bike hangs from its upper spokes, but it doesn't--there's very little tension increase on any spokes when a rider's weight is loaded onto the axle.

    (This is annoying at first, but interesting after you see how it works.)

    As an engineer, you'll probably be interested in these FEA's and strain gauge tests, which show how a pre-tensioned wheel experiences little increase in spoke tension under load.

    Here's a very nice online FEA:

    http://www.astounding.org.uk/ian/wheel/index.html

    Here are references to others, as well as strain gauge readings in figures 10 & 11:

    http://www.duke.edu/~hpgavin/papers/...heel-Paper.pdf

    The main action is the large loss of spoke tension as spokes roll under the hub. The other spokes gain a little tension, but nowhere near what everyone expects, as Ian's detailed analysis shows.

    About the only book that mentions this is Jobst Brandt's "The Bicycle Wheel"--you want the 3rd edition.

    Cheers,

    Carl Fogel

  11. #61
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    Quote Originally Posted by FarHorizon
    Quit repeating this erroneous information. MAVIC SPECS THIS CXP33 RIM FOR UP TO 28MM TIRES!

    Here is the link to Mavic's chart:

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

    The reason Rev. Chuck and I selected this rim originally was for its 36-spokes, strong-V-profile, and nipple ferrules. This was the heaviest-duty rim we could find. This rim is NOT a "lightweight." Don't fault our choices saying we were trying for light weight at the expense of durability - it isn't so.
    Dear FH,

    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 ponts, 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 80-85 psi acting through a 37mm rim, which provides much more leverage than a narrower rim at the same pressure.

    Glad you weren't hurt.

    Cheers,

    Carl Fogel

  12. #62
    Senior Member Deanster04's Avatar
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    Quote Originally Posted by ozbiker
    I note that there are no ferrules in this rim. Each to his own, but I will not ride a rim without ferrules, or some other equivalent destressing arrangement.
    Amen!

  13. #63
    Senior Curmudgeon
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    Quote Originally Posted by carlfogel
    ...it's likely that the rim was simply overwhelmed by the force of 80-85 psi acting through a 37mm tire...
    I'm thinking that you're right, Carl. Thanks for the feedback!

  14. #64
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    Quote Originally Posted by 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.
    The rim surfaces are pristine with no scratching or scoring anywhere.

  15. #65
    Senior Member mattface's Avatar
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    Quote Originally Posted by carlfogel
    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
    Following that link, I noticed all Mavic 700c rims list maximum pressure specs for 19-28mm tires. does that mean they don't make a rim that will handle wider tires?! I would assume that that is just how they list their specs. I know that Open Pros and CXP33 are both used for Cyclocross. You won't find Cyclocross tires that narrow, and I doubt you would see those rims used for Cyclocross if failures like that were commonplace.

    I'm not an engineer, but never having heard of a failure of this kind on ANY rim before that wasn't involved in a massive impact, I would have to assume there was something wrong with the build or more likely the rim itself. If I were the manufacturer, the builder, or the rider of this wheel I'd be very keen to find out the actual cause of the failure in order to avoid having it ever happen again. Probably it took a combination of factors to cause such a spectacular failure, but I think it's a stretch to blame a too wide tire alone.

  16. #66
    Senior Curmudgeon
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    I e-mailed Sheldon Brown personally, asking him to look at this thread and share his opinion. Sheldon says "My guess is either a defective rim or grossly overtensioned spokes." Since we can eliminate overtensioning as a cause, we're left with a defective Mavic. Caveat Emptor!

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    Try a magnified examination of the cracks for some evidence of what happened. A microscope is best but a good magnifying glass will work also. Look at the entire surface of the crack. If there is a difference in color somewhere, you can suspect that there was an existing crack that eventually expanded and led to catastrophic failure. The existing crack will oxidize since it is exposed to the air and have a different color than the rest of the crack.

    Look also for the grain on the crack surface. Most cracks show a grain pattern, see if there is an identifiable pattern to the grain, if so, look for an abrupt change in the grain pattern, that is usually the beginning of the crack because the metal splits in two directions simultaneously, causing different grain patterns. Check especially for grain anomolies around the spoke holes.
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  18. #68
    Senior Curmudgeon
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    Quote Originally Posted by San Rensho
    Try a magnified examination...
    Too late - the carcass is on the way back to Rev. Chuck for diagnosis.

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    Summary of what happened:

    A rider who weighs 275 pounds selected a CPX33 rim, just 19.4mm wide. Mavic lists the rim as "usable" with tires from 19mm wide to 28mm wide. However, "usable" is not "ideal". The ideal tires for the rim were size 23mm to 25mm.

    The rider mounted 37mm tires on the rim. This is about 40% wider than the "ideal" tire, and 30% wider than the widest size allowed for that rim. So, the rider and bike are placing about 300 pounds of load on a rim designed for a typical load in the 140 pound to 200 pound range. Then he mounts a tire that is far, far too wide for the rim. Of course the rim failed. And, it AIN'T Mavic's fault in anyway.

    A 300 pound load is putting "tandem" levels of stress on his rims. And, he ought to be using rims designed for use on a tandem bike...they are designed to carry 300 pound loads, and they are designed for use with 37mm wide tires.

    If a cyclist needs a strong rim, but does not want to use a tandem rim, a touring rim is a workable compromise. The Mavic A719 rim is 24.6mm wide, and a 37mm tire will fit it. That rim weighs only 100 grams more than the CXP33 rim, but would be substantially stronger...strong enough to handle a 300 pound load, IF the wheel is correctly built, and the rider is reasonably careful with the the wheels.

    What happened here was NOT Mavic's fault. It was simply case of a cyclist not being realistic about his needs. A 300 load on a bike creates far more stress than the 180 pounds of stress of the typical 160 pound pro and his 20 pound bike. Equipment that is designed for the Pro peloton is often/usually a TERRIBLE choice for "Joe Average" cyclist. Those of us who are J.A.C. riders need equipment that it tough, reliable, unbreakable. The pro peloton wants light, lighter, and lightest. They have their needs. We have our needs.

  20. #70
    Recovering Retro-grouch CRUM's Avatar
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    I just recently had two wheel repairs go through my shop that may or may not have anything to do with this. One was a rim swap on a Shimano 965 XTR front wheel that had tacoed from what was apparently a small hit. With only 24 15 gauge spokes, I was not overly confident that this wheel was the right choice for the customer. He is an expert who is competing in the NORBA series. The wheel went from my stand into his car and right to North Carolina this past weekend for the race at Sugar Mountain. On a very brutal course, he finished 4th. When I saw the wheel yesterday for re-tweaking, only two spokes needed retensioning and wheel had remained true.

    Second wheel - A Mavic rim that had failed from the inside out. I have never seen this before. The rider is a big guy ( 200 plus) and rode the wheel awhile but noticed it was not round anymore. When I removed the rim tape, the inside wall had cracked and seperated in 2 places, yet the outside was intact. To be fair to the wheel, it had been in service for at least 2 or 3 seasons.

    My point is this. Rims fail for a lot of reasons. Poor materials, poor builds, but most of all the enviroment ridden are all possible reasons. While it would be great to know why this rim failed, I am guessing the real answer will remain hidden among all the possibilities. From the description of the build by Rev Chuck and the experience I know he has, I do not suspect the build. From my experience with thousands of wheels, I do suspect the rim. And that is not a slam on Mavic. They make fine products. But they make thousands and thousands of them. 100% reliability is not reality. Defects happen. Fix it and move on.

    I will say this. As a wheel builder myself, this thread has me looking closer at the wheels I am building now and in the future. It is so very easy to become complacent and cocky doing something you have been doing for so many years. The man who taught me how to drive tractor trailers back in the early 70's gave me a piece of advice I carry to this day. "As soon as you think you know everything about truck driving (wheel building), that is the day you should walk away and never drive (build wheels) again. Thanks for the lesson.
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  21. #71
    The Red Lantern Rev.Chuck's Avatar
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    Beleive me, I have been thinking about whether or not I could have made some kind of gross mistake. The tension could not be off because you have to check it so much and it can't be WAY out in one spot on a brand new rim or the wheel would not be round/true. At work when I build I can get sidetracked, because seeing someone concentrating on a build is an open invitation to start a random conversation, but this wheel was built in my garage with nothing but a radio and some dogs for company. I considered a crooked insert, but they only fit straight in. WHo knows? I have not gotten the wheel yet.
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  22. #72
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    Stuff happens. Sometimes you'll never know why. Get a new wheel, stop worrying, and go ride.

  23. #73
    He drop me Grasschopper's Avatar
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    Well looks like there has been tons of reasons given for the failure...sticking in my head is the tire width issue and from there I will make a suggestion for the next wheel. Salsa Delgado X rims are a box section eyeletted rim with a bit wider width designed for use on 29ers, touring bike, and cyclocross use. 22.5mm rim width to allow use of wider tires. I run them on my commuter in the 32 spoke version but they also have a 36 spoke version...very nice rim IMO...think about it.

    http://www.salsacycles.com/comps_rims.html They are in the QBP catalog.
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  24. #74
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    I'm thinking of using Ambrosio Keba rims (if we can get them).

    Alanbikehouston can blame this wheel failure on tire-size and rider-weight all he wants, but when Sheldon Brown says "either a bad build or a defect" and NOTHING about weight or tire size, I tend to believe Sheldon. Since cyclocross folks routinely use the same Mavic CXP33 rim with wider tires than mine AND at higher pressures than I was running, I tend to think that my particular Mavic rim had a manufacturing defect.

    Rev. Chuck now has the failed wheel with its rim tape, tube, and tire. Hopefully, Chuck can figure out what happened. Chuck says that the likelihood of getting a new rim or any other compensation from Mavic (even if we DO prove that this was caused by a defective rim) is practically zero. Since I'm still dealing with the injury and doctor bills from this, I'm not too happy with Mavic right now.

    My personal solution is to use anything other than Mavic rims on all future bikes. Your life - your choice.

  25. #75
    Senior Member howsteepisit's Avatar
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    I also went through the Mavic charts, all of there rims(even the reflex tubular) have the idential size/pressure chart. Looking at those charts, Mavic does not have a rim that is reccomended or usable for tires over 28 mm. Thats odd says I. I think those charts are laywer charts. Alanbikehouston, what rim would you use for 32 or 37 mm tires?
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