Wrong gear combination results in broken carbon frame :-(

Home Forum Bike Forum Wrong gear combination results in broken carbon frame :-(

Viewing 45 posts - 1 through 45 (of 165 total)
  • Wrong gear combination results in broken carbon frame :-(
  • crikey
    Member

    Get it repaired, then set the chain up properly next time.

    A hanger may not have reduced your bill; I caught a lolly stick in my rear derailleur with took out the hanger, the mech and 6 spokes…

    http://www.carboncyclerepairs.co.uk/index.html

    How did the rear mech pulling back snap the chain stay? Is that just from the force of the mech pulling back?

    Ouch. Expensive lesson to learn 🙁

    GiantJaunt
    Member

    i don’t think the jockey wheel should come into contact with the cassette even with a bizarre gear combination. I hope you get it fixed up ok.

    Carbon repairs nicely. No need for a new frame.

    Must have been a hell of a clunk.

    STATO
    Member

    i don’t think the jockey wheel should come into contact with the cassette even with a bizarre gear combination. I hope you get it fixed up ok.

    A jockey wheel wouldnt as the chain would be straight. What tends to happen tho is the rear part of the mech cage then catches on the next sprocket, resulting it mech death and apparently frame death also tho not sure how, perhaps just too much compression running through frame?

    There are plenty of people in the country who can fix that chain stay for approx £100. Not quite sure how a tight chain caused a snapped chain stay though!

    flanagaj
    Member

    The mistake I have made is that I used the old method of putting the chain over the largest chainring and the largest sprocket without the mech in place. I suspect that method is no longer appropriate.

    Can a frame with so much damage be repaired, the shop say it cannot, but maybe they have a vested interest in flogging me another one.

    The mech is a campag chorus with cutouts in the jockey wheel. The jockey wheel has been destroyed and I think it collapsing was how the rear mech ended up getting sucked around the cassette.

    If the frame can be repaired that will be a big plus.

    Thanks

    Premier Icon scotroutes
    Subscriber

    flanagaj wrote:

    you should be able to use any gear combination on the bike

    +1f

    Always worth checking after everything is fitted too

    andrewh
    Member

    Looks repairable to me, will be a couple of hundred to have it done properly but better than a new frame! I had a snapped chainstay repaired last year, not pretty as they couldn’t match the mottled effect of the original without some serious work to a much bigger area but functionally it’s fine, which is the main thing

    boblo
    Member

    Bloody hell, bad luck. Did you use big/big plus two links and then check it? You must have legs like Garth if you managed to kill a chainstay with brute (ooo get you) force.

    Go to a specialist menders and ignore your LBS.

    umop3pisdn
    Member

    The mistake I have made is that I used the old method of putting the chain over the largest chainring and the largest sprocket without the mech in place. I suspect that method is no longer appropriate.

    It works, you just forgot to add 2 links.

    TurnerGuy
    Member

    I prefer the big/big plus 4 links and then have a look and see if it is actually too big, then only take that extra 2 links off if it is…

    flanagaj
    Member

    Cheers fellas. I can dry my tears now in the knowledge that it can be repaired.

    When I rebuild it next time I will double check that large sprocket + large chain ring does not equal jockey wheel or mech getting jambed up in the cassette.

    lightman
    Member

    Can a frame with so much damage be repaired, the shop say it cannot, but maybe they have a vested interest in flogging me another one.

    Maybe time to look for a new shop or give them links to repairers and educate them!

    I have seen pictures of bikes that have been broken in two, and they have been repaired.
    Your repair should cost no more than £100 not including postage if needed.
    Or, buy a repair kit and do it yourself!

    flanagaj
    Member

    Given I have vacuum bagging equipment from repairing my windsurf boards, I probably could do it myself. I think I will pass though as a windsurf board repair is not quite as important as a road bike structural repair.

    flanagaj
    Member

    I was out on a ride today and changed gear on a hill. Unfortunately, I was on the 50 ring at the front and went too high on the rear cassette. Result was that the rear mech jockey wheel contacted with the cassette tooth and ripped the rear mech back behind the cassette. End result is shown in the picture. If the frame manufacturer had used a replaceable hanger I would have had a £20 bill, now I need to find £1800 to replace the frame.

    Spoke to the shop and they told me it’s my own fault for having the chain too short and that you should be able to use any gear combination on the bike.

    Really annoyed about this.

    Edric 64
    Member

    Steel is real, you might have a dent but not a fubbarred frame made from chocolate

    Premier Icon takisawa2
    Subscriber

    Bad luck chap.
    Should fix up fine.

    I’m in awe of your use of a 50t ring off road. 😕

    Steel is real

    Didn’t take long. Boring chat.

    Big Dave
    Member

    Steel is real

    I once snapped a steel framed Dawes tourer. Not through crashing it either…

    IanMunro
    Member

    Spoke to the shop and they told me it’s my own fault for having the chain too short and that you should be able to use any gear combination on the bike.

    They’ve got a point. Not really what you needed to hear at the time though 🙁
    Saw a rear mech die in a similar manner on a full-suss bike where the chain was just long enough when put on the bike, but not long enough when the suspension was fully compressed.

    Oooft that’s nasty, feel your pain!

    What frame was it? Curiosity really.

    nickhart
    Member

    as matt holme says how did the rear mech going back break the chainstay and so cleanly too?
    what manufacturer is it and how old is it? a mate picked up a broken scott (similar place) and had it fixed and it’s probably better than new now!
    maybe it wasn’t the chain but the amount of power you’re putting down!

    chief9000
    Member

    That looks like some serious damage there. Was there some impact there? or is it just result of a huge pedaling moment and a sudden stop?

    If you are looking to get it repaired, just be aware that there could also be damage in other places that you may not be able to see. Have a good look at the rear lugs and also all the rear stays. Just to be of the safe side.

    What bike is it out of interest ?

    It’s carbon, and a road bike, no sympathy from me 😉

    In all seriousness, I’d be devastated if I’d done that, could have been a lot worse though!

    flanagaj
    Member

    Well spotted. It is my Argon 18 Gallium Pro road bike. Was flying along about 25mph in Poole and then came to a sharp climb so sprinted the hill and then shifted up a couple on the rear. Back wheel suddenly locks up and I skid to a halt on the hill. Rear mech is wrapped around the cassette and partially jambed in the back wheel.

    Thought to myself, what the heck that looks wrong, and then spotted the chainstay snapped cleanly across.

    It must have exerted serious laterally twist on the rear triangle for the chainstay to fail. That is my only concern that the shear twist involved to have snapped it may have weakened the fibres elsewhere on the rear.

    ps – I am a mountain biker mainly. Just like the road once in a while

    dirtyrider
    Member

    I was on the 50 ring at the front

    thats your problem

    ive got a repaired supersix high mod – bars stuffed a whole in the toptube – carbon reapirs used, frame looks fine now, ive not refinished it either

    Steel is real, you might have a dent but not a fubbarred frame made from chocolate

    Seems pretty much every steel road frame eventually cracks the BB shell, got one in the garage that’s been brazed up, carbon repairable at comparable cost to getting new steel tubes fitted.

    oldgit
    Member

    One of the LVRC guys has a Pinarello that’s been repaired three times now by that ^ company, it’s still being raced.

    Is it not poor form anymore to run big-big? We have a big lad that keeps using that combo and I thought that’s why he goes through so many BB30s, hangers and mechs?

    crikey
    Member

    The only advantages that steel had over carbon was its better impact resistance and its repairability. It looks like the repairability is becoming less of an issue. Given the use of high end, heat treated, difficult to work steels, the gap narrows even more.

    I’ve broken steel frames and aluminium frames beyond economic repair, but the idea that ‘fragile’ (actually not), ‘plastic’ (actually not), frames can be repaired is great.

    So maybe the stay snapped first, I snapped a steel chainstay once and when putting power in the rear mech went into the rear wheel as the whole lot twisted.

    flanagaj
    Member

    That is a very interesting theory. The rear mech was wedged in the rear wheel as that too is buckled.

    I do find it strange that I could bust one chainstay so badly. If the whole back end had twisted so hard then I would have also expected to have damaged the stay on the other side, but that is fine.

    Trouble is, who will believe that theory.

    The only advantages that steel had over carbon was its better impact resistance and its repairability.

    The top tube on my two month old steel hardtail would be to differ, wobbled over between two sheffield stands whilst locking up and put a dent in it 🙁

    Round someones house and he showed me his new race bike for this year, the top tube was soft enough to flex under your thumb like a tyre! I bet it would have shrugged off the bike stand!

    mk1fan
    Member

    Didn’t know carbon was so ‘fixable’.

    Maybe one day I’ll treat myself to one or maybe Ti.

    flanagaj
    Member

    I have been thinking about this a bit more now and I am struggling to understand how the rear wheel locking as a result of the rear mech getting caught in the rear wheel / on the cassette would cause such failure in the chain stay.

    Surely the wheel should have just locked up and that’s it?

    Shop are not interested so am going to speak with manufacturer next week about this or even another bike shop to see what they say

    ads-b
    Member

    Is it possible it was the other way round? Frame snapped, forcing the mech in to the rear wheel? Id go with that anyway and go for a warranty replacement on that basis.

    flanagaj
    Member

    Good question, but LBS are saying nope it’s your fault. I will speak with Tri UK again tomorrow about this as I am not happy as I don’t think such a situation should have resulted in a snapped chainstay.

    Rorschach
    Member

    “Hi,I am very unhappy.I set my bike up with too short a chain and it broke because of it.I think my frame should not break when I do something stupid to it,can I have a new one please?”
    What could go wrong?

    flanagaj
    Member

    “Hi,I am very unhappy.I set my bike up with too short a chain and it broke because of it.I think my frame should not break when I do something stupid to it,can I have a new one please?” – See below

    If someone can explain why having too short a chain would cause a chainstay to snap then I will gladly take the medicine, but otherwise I will question the reason for the failure.

    Any structural engineers out there who could give a layman’s explanation as to why this caused such a failure then please do post.

    Thanks

    trail_rat
    Member

    Rear mech whipped up nto the stay by your cranking it

    Creates a sharp point impact into the chainstay

    I have seen exactly this happen on an mtb in the past

    * edit – was much closer to the rear axel than that though

    flanagaj
    Member

    Nope, I pushed the rear mech up under the frame to test this theory and like you say the impact point would have been much further back if that was the cause.

    trail_rat
    Member

    Also , do any of these carbon repair companies offer any kind of warrenty or guarantee the rest of the frame is ok.

    If not i would not recomend a customer to pursue this option either.

    Greybeard
    Member

    I can’t see the big ring resulting in excess chainstay load. Thinking about the leverage, for the same pedal force, the chain force with a 50T ring is only half what it is with a 25T. Big-big is better than small-small for chain (and hence chainstay) load. Quite frightening actually – not a road biker so don’t know what size small chainring is, but if it’s 110 diameter (55mm radius) and you have 175 cranks, and put your full body weight on the pedal, the chain tension is over 3 times your weight.

    But, Big-big does put the chain quite diagonal, and so puts a sideways load on the mech. If the chain is a bit short, so the mech is lying almost horizontally forwards, the chainring to mech distance gets even shorter and the diagonal angle is greater – with the chain pulling sideways from the big ring, it wouldn’t surprise me if the mech bent or the jockey wheel gave way. Not quite sure what breaks next but something will.

    walleater
    Member

    Sounds to me that the lower limit screw on the derailleur wasn’t adjusted properly, and either the chain came off the back of the cassette, or more likely the derailleur cage caught a spoke under heavy torque.

Viewing 45 posts - 1 through 45 (of 165 total)

The topic ‘Wrong gear combination results in broken carbon frame :-(’ is closed to new replies.