Mavic SLR wheels / spokes - theory

seanwilliams158
seanwilliams158 Posts: 8
edited August 2013 in Road general
more detail and an un-qualified theory.
My 3 week old mavic SLR rear wheel failed buring this year's Marmotte. A rear, block side spoke went twice. One at the start of The Telegraph and one again 4km from the top of Galibier.... ( a Mavic van/engineer fixed the first breakage at a feed station half way up ).
Obviously these failures spoilt my day !
My theory involves - speed, weight and metal.
I am 88kgs, i was going slowly up approx 10% gradient and it was 39C in the sun ( as measured on my garmin ).
I think going slowly, pushing hard in high temperatures, these wheels do not work. Aluminium expands twice as much as iron under heat and when these spokes broke they broke at both ends simultaneously and "pinged" across the road.... they were under too much stress.....( from my weight, the force needed to propel me and the expansion of the material )
This is my theory and Mavic will not comment - they just say these things happen !!
Just to state - i have have used Mavic wheels for as long as i can remember with no problems - i will never use these SLR's again however because i believe they are flawed for hot, slow climbs for heavy(ish) guys like me.

Comments

  • Monty Dog
    Monty Dog Posts: 20,614
    Straightforward, stresses on wheel exceeded the design limit leading to rapid failure - most likely due to a poor batch of spokes e.g. Manufacturing or material defect. As they are only new, I'd take them back to shop and reject them as being ubfit for purpose and ask for refund - they then have to produce the evidence to say they were. Your contract is with the shop not Mavic, so don't let them fob you off.
    Make mine an Italian, with Campagnolo on the side..
  • Rob Somerset
    Rob Somerset Posts: 127
    Sounds like a manufacturing/material fault to me. How many miles had you done on them before they broke? Were they running true and not creaking before the event.
    The temperature thing I think is irrelevant. 25deg C temperature change will cause about 0.1mm change in the spoke length which wont affect anything (also the diameter of the wheel is also expanding to match ). If it were the case then everyones spokes would ping off. 39 degrees may feel hot to you but its not to a piece of metal. , consider also that on the Glandon downhill the rims were probably at more than 60 deg due to braking.
    FWIW my cheap pair of Askiums got me round on that ride with no trouble ;)
    Rob
    Hills do make I sweat a lot
  • ugo.santalucia
    ugo.santalucia Posts: 28,302
    Sean, the topic has been extensively discussed in the previous thread you opened last week (and never really got involved... :evil: )
    I stated my point on zicral back then and I won't do it again as it seems there is a Mavic Brigade who gets very offended. Got enough abuse back then...

    As a piece of advice, try to revive the existing topics and get involved, instead of opening new ones... :wink:
    left the forum March 2023
  • estampida
    estampida Posts: 1,008
    was it a forward or rear facing spoke?
  • seanwilliams158
    seanwilliams158 Posts: 8
    Ugo... thanks for the advce and the previous posts... i appreciate the responses you gave and certainly learnt a lot about the subject.
    off to find a new wheel !
    ps.. i don't know which way the spokes were facing sorry...
  • sloppyschleckonds
    sloppyschleckonds Posts: 8,019
    seanwilliams158 wrote:
    off to find a new wheel !

    I have a set of Ksyrium/ R-Sys SLR's I am selling, they've done about 5000 miles. Just had the bearings replaced, although the shop handed me back the replaced ones saying they didn't need doing. Have never needed truing either.
    PM if interested.
    I'm sorry you don't believe in miracles
  • robbo2011
    robbo2011 Posts: 1,017
    ugo.santalucia wrote:
    Sean, the topic has been extensively discussed in the previous thread you opened last week (and never really got involved... :evil: )
    I stated my point on zicral back then and I won't do it again as it seems there is a Mavic Brigade who gets very offended. Got enough abuse back then...

    As a piece of advice, try to revive the existing topics and get involved, instead of opening new ones... :wink:

    Yeah, but your point was that the strength of the Zicral spokes is irrelevent as they are strong enough, it's the fatigue that is the problem. After 3 weeks of use they are hardly likely to be fatigued, are they?

    There does seem something up with the SLR design though, you hardly ever read of failures on other designs like the SL.
  • ugo.santalucia
    ugo.santalucia Posts: 28,302
    robbo2011 wrote:
    ugo.santalucia wrote:
    Sean, the topic has been extensively discussed in the previous thread you opened last week (and never really got involved... :evil: )
    I stated my point on zicral back then and I won't do it again as it seems there is a Mavic Brigade who gets very offended. Got enough abuse back then...

    As a piece of advice, try to revive the existing topics and get involved, instead of opening new ones... :wink:

    Yeah, but your point was that the strength of the Zicral spokes is irrelevent as they are strong enough, it's the fatigue that is the problem. After 3 weeks of use they are hardly likely to be fatigued, are they?

    There does seem something up with the SLR design though, you hardly ever read of failures on other designs like the SL.

    Could be the design make them fatigue early. If you do 500 miles, that's about 400,000 revolutions of the wheel... crap design, inadequate materials, and inappropriate load can cause fatigue at 400K cycles.
    Technically, any spoke failure is fatigue, as they never experience a stress superior to the yield one
    left the forum March 2023
  • diy
    diy Posts: 6,473
    If these are under six month old simply reject them back to the shop and get a refund less benefit of use. Given the high purchase cost and risk of injury due to failure there should be a straight forward claim against the retailer.

    If they are over six month old then it might be a little harder. But act quickly either way and stop analysing why they failed.
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  • navrig
    navrig Posts: 1,352
    seanwilliams158 wrote:
    more detail and an un-qualified theory.
    My 3 week old mavic SLR rear wheel failed buring this year's Marmotte. A rear, block side spoke went twice. One at the start of The Telegraph and one again 4km from the top of Galibier.... ( a Mavic van/engineer fixed the first breakage at a feed station half way up ).
    Obviously these failures spoilt my day !
    My theory involves - speed, weight and metal.
    I am 88kgs, i was going slowly up approx 10% gradient and it was 39C in the sun ( as measured on my garmin ).
    I think going slowly, pushing hard in high temperatures, these wheels do not work. Aluminium expands twice as much as iron under heat and when these spokes broke they broke at both ends simultaneously and "pinged" across the road.... they were under too much stress.....( from my weight, the force needed to propel me and the expansion of the material )
    This is my theory and Mavic will not comment - they just say these things happen !!
    Just to state - i have have used Mavic wheels for as long as i can remember with no problems - i will never use these SLR's again however because i believe they are flawed for hot, slow climbs for heavy(ish) guys like me.


    If bicycle wheels were design this close to the limit the courts would be full of law suits involving badly injured people and the manufacturers. I am afraid to say your theory is way off and completely unfounded.

    You bought a wheel with a manufacturing flaw - as advised above seek a replacement and make sure you quote the various pieces of consumer protection legislation.
  • navrig
    navrig Posts: 1,352
    ugo.santalucia wrote:
    Technically, any spoke failure is fatigue, as they never experience a stress superior to the yield one

    I doubt this is correct especially if the spoke tension is set incorrectly. In that case it is quite feasible for spokes to be over stressed and snap without suffering fatigue.
  • ugo.santalucia
    ugo.santalucia Posts: 28,302
    Navrig wrote:
    ugo.santalucia wrote:
    Technically, any spoke failure is fatigue, as they never experience a stress superior to the yield one

    I doubt this is correct especially if the spoke tension is set incorrectly. In that case it is quite feasible for spokes to be over stressed and snap without suffering fatigue.


    Mmmhh, any decent spoke will take 2000 N without bulging... at that tension the rim will be ripped apart and no nipple can be turned to that kind of tension, so even the wheels with the highest tension are built at 1600-1700.
    If on the contrary the tension was too low, then every revolution will cause the spoke to bend a bit more and eventually develop cracks quicker... which is fatigue, really...
    left the forum March 2023

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