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Drive-side Ultegra crank arm weirdness – is this dangerous or cosmetic?

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  • December 3, 2019 at 1:30 am #30314
    terrycojones

    I was doing a hard uphill (virtual) ride last night with a lot of out-of-saddle riding. I noticed my right pedal felt increasingly odd and thought that the pedal might somehow be coming off. After the ride I had a look and found what’s shown in the two pictures at http://jon.es/other/ultegra-crank-1.jpg and http://jon.es/other/ultegra-crank-2.jpg. What looked initially like just a cover was quite a bit further off than is shown in the images. At first I thought it was just a cosmetic thing and so I tapped (firmly) with a hammer on the 4 stubby arm-like sections that were coming away from the chain rings (the top-left arm in the 1st photo shows a pretty wide gap). They went back in to some degree, but as you can see in the photos that they’re still not flush with the outer body of the rest of the front rings. But then I thought “hang on, if that’s just a cosmetic cover, why did your pedalling start to feel so wonky & messed up?”  So now I’m guessing that that central 4-armed piece is actually integral to the whole ringset body and that maybe I’m in danger of having it completely break apart.

    Has anyone experienced this before? It’s Ultegra 6800, I believe. I’ve done over 20,000 km on it, so it’s not exactly new. I changed the chain rings a few years back, but as far as I remember that didn’t involve changing the part that now looks like it’s about to break off / fall apart.

    Thanks for any help / suggestions!

     

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  • January 21, 2020 at 1:09 pm #953509
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    Daveyraveygravey

    Thatsnotmyname wrote:

    Thatsnotmyname wrote:
    brooksby wrote:

    Thatsnotmyname wrote:
    As others have said – the notion that this is related to use on a turbo is just nonsense.  Turbo use would not affect this, or any other crankset.

    Why not? Isn’t using a turbo almost the same thing as just riding the bike, and if it can happen when riding the bike, then…? 

    Well, it could happen while on a turbo, but the turbo would still not be the root cause..

     

    …and the troll was saying it ONLY happens on a turbo, because the back wheel is fixed and can’t move around like a bike would on the road kiss  It happens because pedals are turning crank arms, and some of these haven’t been stuck together too well.

    January 17, 2020 at 9:43 pm #953507
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    Thatsnotmyname

    brooksby wrote:

    brooksby wrote:

    Thatsnotmyname wrote:
    As others have said – the notion that this is related to use on a turbo is just nonsense.  Turbo use would not affect this, or any other crankset.

    Why not? Isn’t using a turbo almost the same thing as just riding the bike, and if it can happen when riding the bike, then…? 


    Well, it could happen while on a turbo, but the turbo would still not be the root cause..

    January 17, 2020 at 2:25 pm #953505
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    brooksby
    Thatsnotmyname wrote:
    As others have said – the notion that this is related to use on a turbo is just nonsense.  Turbo use would not affect this, or any other crankset.

    Why not? Isn’t using a turbo almost the same thing as just riding the bike, and if it can happen when riding the bike, then…? 

    January 17, 2020 at 1:02 pm #953503
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    Daveyraveygravey
    Thatsnotmyname wrote:
    https://www.cyclechat.net/threads/turbo-trainer-hybrids.256356/
    😉
     

     

     

    What a tosser!  

    January 15, 2020 at 5:13 pm #953501
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    Thatsnotmyname

    As others have said – the

    As others have said – the notion that this is related to use on a turbo is just nonsense.  Turbo use would not affect this, or any other crankset.

    January 15, 2020 at 2:06 pm #953499
    0
    Nick T

    It’s a failure at the point

    It’s a failure at the point of chemical bonding between the two halves of the crank arm, and it’s relatively well documented. The cause hasn’t been established, it could be environmental such as using degreasers on the component, manufacturing fault, or “unsympathetic” use. I don’t believe turbo use would exacerbate the problem, if anything it would prevent it – side loads are minimised when the bike is secured, Putting less strain on the adhesive than when leaning the bike heavily in a sprint for example 

    January 15, 2020 at 1:22 pm #953497
    0
    Thatsnotmyname

    https://www.cyclechat.net

    https://www.cyclechat.net/threads/turbo-trainer-hybrids.256356/
    😉
     

     

    January 15, 2020 at 1:14 pm #953495
    0
    Daveyraveygravey
    Judge dreadful wrote:
    Daveyraveygravey wrote:
    Yup, utter b/s

    The website and my phone weren’t getting on last night…

    My bike has never been near a turbo, this is a pretty common fault.  I don’t believe it is use on a turbo that is causing it; it may be making it happen more often, but I don’t think that explanation makes sense.

    OP, take the bike back to the shop you bought it from and start with them.  This could have had nasty consequences for you if it had let go when you were on a big effort, and it is not an acceptable failure.  The shop where I bought my bike from put me in touch with Madison, the UK distributor, and I eventually got a free replacement even though it was a year outside the warranty.

     

     

    Youre also wrong. The fault may ( and does ) occur on the road, putting the bike on the turbo helps it along nicely.

     

    How am I wrong?  My bike has NEVER been on a turbo.

    January 4, 2020 at 9:24 pm #953493
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    Judge dreadful
    Daveyraveygravey wrote:
    Yup, utter b/s

    The website and my phone weren’t getting on last night…

    My bike has never been near a turbo, this is a pretty common fault.  I don’t believe it is use on a turbo that is causing it; it may be making it happen more often, but I don’t think that explanation makes sense.

    OP, take the bike back to the shop you bought it from and start with them.  This could have had nasty consequences for you if it had let go when you were on a big effort, and it is not an acceptable failure.  The shop where I bought my bike from put me in touch with Madison, the UK distributor, and I eventually got a free replacement even though it was a year outside the warranty.

     

     

    Youre also wrong. The fault may ( and does ) occur on the road, putting the bike on the turbo helps it along nicely.

    January 4, 2020 at 9:22 pm #953491
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    Judge dreadful
    Drinfinity wrote:
    Judge dreadful wrote:
    You’ve got a problem caused by the abnormal torsion you exert on the cranks, when pushing hard, on a bike which can’t move ‘naturally’ because it’s stuck in a turbo. The lighter / better the cranks, the worse it gets. I’m seeing this sort of damage / issue more and more, as the popularity of turbo type riding increases. A rocking / dynamic tilt turbo, and / or rollers, are a better option.

    How is that the case? If you put force down on the pedal, yes, you are putting torque on the crank which is trying to twist it. However the proportion of that torque which would be relieved by accelerating the rotation of the bike towards the pedal if you were riding on road compared to a turbo is negligible- otherwise your power would go into spinning your bike onto its side.

    I would agree that fixing a bike at the rear and putting the power down might make a difference at the seat stay, but not in the crank. 
     

    The failure is an unacceptable defect, nothing to do with a turbo trainer.

     

    you’re wrong.

    December 5, 2019 at 3:19 pm #953489
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    Hirsute

    terrycojones wrote:

    terrycojones wrote:

    I took everything apart. Looks like this can be fixed relatively cheaply, via one of these https://www.ebay.co.uk/itm/Shimano-Ultegra-6800-170-mm-crank-arm-chainset-NEW/264543368875


    Thanks, now I’m getting emails to buy this !!

    December 5, 2019 at 12:48 pm #953487
    0
    Daveyraveygravey

    Yup, utter b/s

    Yup, utter b/s

    The website and my phone weren’t getting on last night…

    My bike has never been near a turbo, this is a pretty common fault.  I don’t believe it is use on a turbo that is causing it; it may be making it happen more often, but I don’t think that explanation makes sense.

    OP, take the bike back to the shop you bought it from and start with them.  This could have had nasty consequences for you if it had let go when you were on a big effort, and it is not an acceptable failure.  The shop where I bought my bike from put me in touch with Madison, the UK distributor, and I eventually got a free replacement even though it was a year outside the warranty.

     

     

    December 4, 2019 at 6:39 pm #953485
    0
    Anonymous

    Judge dreadful wrote:

    Judge dreadful wrote:

    You’ve got a problem caused by the abnormal torsion you exert on the cranks, when pushing hard, on a bike which can’t move ‘naturally’ because it’s stuck in a turbo. The lighter / better the cranks, the worse it gets. I’m seeing this sort of damage / issue more and more, as the popularity of turbo type riding increases. A rocking / dynamic tilt turbo, and / or rollers, are a better option.


    Haha! Err, no.

    December 4, 2019 at 5:33 pm #953483
    0
    Drinfinity
    Judge dreadful wrote:
    You’ve got a problem caused by the abnormal torsion you exert on the cranks, when pushing hard, on a bike which can’t move ‘naturally’ because it’s stuck in a turbo. The lighter / better the cranks, the worse it gets. I’m seeing this sort of damage / issue more and more, as the popularity of turbo type riding increases. A rocking / dynamic tilt turbo, and / or rollers, are a better option.

    How is that the case? If you put force down on the pedal, yes, you are putting torque on the crank which is trying to twist it. However the proportion of that torque which would be relieved by accelerating the rotation of the bike towards the pedal if you were riding on road compared to a turbo is negligible- otherwise your power would go into spinning your bike onto its side.

    I would agree that fixing a bike at the rear and putting the power down might make a difference at the seat stay, but not in the crank. 
     

    The failure is an unacceptable defect, nothing to do with a turbo trainer.

    December 4, 2019 at 5:03 pm #953481
    0
    terrycojones

    I have a Tacx Neo 2 Smart,

    I have a Tacx Neo 2 Smart, which in theory does let you rock left/right – but maybe not enough.

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