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Chain Issues

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  • 10-03-2017 6:31am
    #1
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭


    I changed my chain last night. Bought an 11 speed KMC chain. Measured against the old chain and cut it.

    Out for a ride this morning and the chain wouldn't stay on. Kept jumping off the big ring when any power was put into the pedals. Spins fine under small loads. I assume I have cut it two short?
    Many thing else it might be?


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    #2
    TonyStark
    Registered Users Posts: 851 ✭✭✭TonyStark


    godtabh wrote: »
    I changed my chain last night. Bought an 11 speed KMC chain. Measured against the old chain and cut it.

    Out for a ride this morning and the chain wouldn't stay on. Kept jumping off the big ring when anyboowrr was out into the pedals. Spins fine under small loads. I assume I have cut it two short?
    Many thing else it might be?

    What does it look like on the four combinations? BF = biggest front, BR = biggest rear, SF = smallest front, SR = smallest rear

    BF - SR
    BF - BR
    SF - SR
    SF - BR

    Is there much slack? Ultimately sounds like a FD tweak with limiting screws?


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    #3
    smacl
    Moderators, Society & Culture Moderators Posts: 15,754 Mod ✭✭✭✭smacl


    Possibly chain direction related, although this should no be the case for KMC 11 speed. As TonStark mentioned, adjusting the FD screws should stop the chain drop, but if it is already in the big ring and drops when you apply pressure there it sounds like another underlying problem, such as wear on the big ring causing the teeth not to engage properly with the chain. A slightly loose crank might also cause this.


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    #4
    07Lapierre
    Registered Users Posts: 8,248 ✭✭✭07Lapierre


    Worn chainring?


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    #5
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    07Lapierre wrote: »
    Worn chainring?

    Chain is brand new. Will check the FD.

    I'm more worried about the sound it makes before jumping. There is a big grinding noise or some such


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    #6
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    TonyStark wrote: »
    What does it look like on the four combinations? BF = biggest front, BR = biggest rear, SF = smallest front, SR = smallest rear

    BF - SR
    BF - BR
    SF - SR
    SF - BR

    Is there much slack? Ultimately sounds like a FD tweak with limiting screws?

    just checked when its SF - SR there is a lot of slack.


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    #7
    07Lapierre
    Registered Users Posts: 8,248 ✭✭✭07Lapierre


    godtabh wrote: »
    Chain is brand new. Will check the FD.

    I'm more worried about the sound it makes before jumping. There is a big grinding noise or some such

    No the chainring! I know your chain is new, but if the big chainring is worn, the chain will jump off when under load.


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    #8
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    07Lapierre wrote: »
    No the chainring! I know your chain is new, but if the big chainring is worn, the chain will jump off when under load.

    Chainring has maybe 5-6k km on it. Brand new casettee


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    #9
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    Assuming that the chain is the right length i wonder is the rear deraileur not taking the full tension. When I was changing the chain I noticed the jokey wheels were full of gunk. Will give it a proper clean tonight


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    #10
    smacl
    Moderators, Society & Culture Moderators Posts: 15,754 Mod ✭✭✭✭smacl


    godtabh wrote: »
    Chainring has maybe 5-6k km on it. Brand new casettee

    A worn chainring is visible as the front of the teeth (i.e. the side that takes the load) are visibly more worn than the back. If there is any play on the crank you could get a similar problem, e.g. worn BB bearings.


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    #11
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    smacl wrote: »
    A worn chainring is visible as the front of the teeth (i.e. the side that takes the load) are visibly more worn than the back. If there is any play on the crank you could get a similar problem, e.g. worn BB bearings.

    BB was replaced yesterday. Asked the bike shop to give it a once over when it was in and they said they didn't notice any issues


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    #12
    smacl
    Moderators, Society & Culture Moderators Posts: 15,754 Mod ✭✭✭✭smacl


    godtabh wrote: »
    BB was replaced yesterday. Asked the bike shop to give it a once over when it was in and they said they didn't notice any issues

    Could be the crank is sitting slightly further in on the new BB so, which just means the FD needs to be readjusted slightly (limit screws & tension if you get any rub).


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    #13
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    smacl wrote: »
    Could be the crank is sitting slightly further in on the new BB so, which just means the FD needs to be readjusted slightly (limit screws & tension if you get any rub).

    I only had time for a quick look this morning but the FD looks ok where it is. I'll have a proper look tonight


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    #14
    ford2600
    Closed Accounts Posts: 4,457 ✭✭✭ford2600


    Best guess is you cut chain too short.

    A BR BC combo has overextended RD.

    Lbs time.

    If you are not cleaning drivetrain when fitting new chain perhaps DIY is not for you


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    #15
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    ford2600 wrote: »
    Best guess is you cut chain too short.

    A BR BC combo has overextended RD.

    Lbs time.

    If you are not cleaning drivetrain when fitting new chain perhaps DIY is not for you

    The drive train gets cleaned once a week/every 200km. It does get gunked up from time to time due to conditions


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    #16
    07Lapierre
    Registered Users Posts: 8,248 ✭✭✭07Lapierre


    godtabh wrote: »
    I changed my chain last night. Bought an 11 speed KMC chain. Measured against the old chain and cut it.

    Out for a ride this morning and the chain wouldn't stay on. Kept jumping off the big ring when any power was put into the pedals. Spins fine under small loads. I assume I have cut it two short?
    Many thing else it might be?

    How did you measure it? by length or no. of links? Worn chains stretch. I lay new and old chain beside each other and count the no. of links. New chain should have the same number of links as the old chain.


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    #17
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    07Lapierre wrote: »
    How did you measure it? by length or no. of links? Worn chains stretch. I lay new and old chain beside each other and count the no. of links. New chain should have the same number of links as the old chain.

    Crap. Never thought of that. I measured side by side


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    #18
    easygoing39
    Registered Users Posts: 1,375 ✭✭✭easygoing39


    Measuring side by side is fine.A stretched chain wont grow by inch's!!!!!


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    #19
    07Lapierre
    Registered Users Posts: 8,248 ✭✭✭07Lapierre


    easygoing39 wrote: »
    Measuring side by side is fine.A stretched chain wont grow by inch's!!!!!

    No but it would explain why there is a lot of slack when the chain is on the small chainring and small sprocket. I can't see it being a cause of the "Jumping" fault though.


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    #20
    smacl
    Moderators, Society & Culture Moderators Posts: 15,754 Mod ✭✭✭✭smacl


    07Lapierre wrote: »
    No but it would explain why there is a lot of slack when the chain is on the small chainring and small sprocket. I can't see it being a cause of the "Jumping" fault though.

    Same, worn chainring, crank position after new BB fitted or combination of both for my money.


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    #21
    captain_boycott
    Registered Users Posts: 539 ✭✭✭captain_boycott


    easygoing39 wrote: »
    Measuring side by side is fine.A stretched chain wont grow by inch's!!!!!

    actually, I replaced a chain on my bothers old hybrid recently, and granted that he nhad not replaced the chain in years, when measured side by side versus counting the links - the old chain was stretched well over an inch.

    I found using the calculation method, as described in the video here worked perfectly to get the correct length. https://www.youtube.com/watch?v=Vg2SoOOrpE8


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    #22
    CramCycle
    Moderators, Sports Moderators Posts: 24,940 Mod ✭✭✭✭CramCycle


    Take a pic of the teeth on the chainring, that would be my guess by the description.


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    #23
    doozerie
    Registered Users Posts: 4,830 ✭✭✭doozerie


    Just some random thoughts to add to the suggestions already made:

    * is the chainset an 11sp or 10sp?
    * if the cassette is brand new too is there any chance that an inner washer was added or removed in the process? If so then your chainline will likely have changed.
    * likewise, is there any chance that a washer was added/removed when the new b/b was installed? Again that would change the chainline too.
    * is the new cassette the same ratios as the old one? If not did you adjust the derailleur screw that controls how close the upper jockey wheel is to the cassette accordingly? Or did you double check it if you replace like with like?
    * is the spring on the jockey wheel cage of the rear derailleur working properly or it is sticking?
    * check the jockey wheels to see if they are spinning properly. I recently had odd problems (but different to yours) which were caused by the bearings in the lower jockey wheel being shot.


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    #24
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    I took a link off the chain. Still same issue.

    The fact I took another link off suggests to me that the orginal chain was much more worn out than I thought. I last check it in around Nov. Got ridden a lot in bad weather since.

    I also did my sums. THe chainrings have at least 10k km on it. I reckon the old chain wore the chainrings badly and the new chain and old chainrings dont get on. Will be brining it back to get the chainrings replaced.

    Its a 11 speed 6800 setup


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    #25
    ford2600
    Closed Accounts Posts: 4,457 ✭✭✭ford2600


    godtabh wrote: »
    I took a link off the chain. Still same issue.

    The fact I took another link off suggests to me that the orginal chain was much more worn out than I thought. I last check it in around Nov. Got ridden a lot in bad weather since.

    I also did my sums. THe chainrings have at least 10k km on it. I reckon the old chain wore the chainrings badly and the new chain and old chainrings dont get on. Will be brining it back to get the chainrings replaced.

    Its a 11 speed 6800 setup

    If the whole drivetrain is that fcuked I'd be inclined to leave on old chain until it's getting close to skipping. Everything is pretty matched at that stage.

    I didn't think worn chainrings was possible at 5-6k or even 10k with any care

    There is an argument to running a drivetrain into the ground like that, it probably makes more sense at the Sora end of spectrum rather than Ultegra through.

    On a single speed with even number cogs front and rear you can really act the bo11ix and get away with 3% wear or thereabouts

    On a good bike, it doesn't take much care for a crankset to last almost indefinitely. I've about 50k on my current road crank with low enough care


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    #26
    Pinch Flat
    Registered Users Posts: 7,762 ✭✭✭Pinch Flat


    Sounds to me like the chain is too long - measuring it off the old chain is wrong, as it will have stretched. Does it sag a bit between the cassette and from chain ring where the chain is nearest the ground?

    I use sheldonbrowns's guide for chain length - worked a dream to date:

    http://www.sheldonbrown.com/derailer-adjustment.html#chain


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    #27
    Hungrycol
    Registered Users Posts: 2,246 ✭✭✭Hungrycol


    A stiff link or the power link not in correctly?


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    #28
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,218 Mod ✭✭✭✭godtabh


    Its back in the bike shop waiting for a chainring. Hard to source seemingly


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    #29
    Wishbone Ash
    Registered Users Posts: 24,995 ✭✭✭✭Wishbone Ash


    Pinch Flat wrote: »
    Sounds to me like the chain is too long - measuring it off the old chain is wrong, as it will have stretched...
    A worn chain is only a few mm longer than a new one. I always measure my new chains against the old one to know where to break the new one. I don't understand why you think measuring against the old one is wrong - it doesn't grow several links as it wears!


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    #30
    Pinch Flat
    Registered Users Posts: 7,762 ✭✭✭Pinch Flat


    Wishbone Ash wrote: »
    A worn chain is only a few mm longer than a new one. I always measure my new chains against the old one to know where to break the new one. I don't understand why you think measuring against the old one is wrong - it doesn't grow several links as it wears!

    Fair enough, maybe I'll try this the next time I change my chain. Just sort of got used to the technique Sheldon Brown describes.


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    #31
    cython
    Registered Users Posts: 4,769 ✭✭✭cython


    What WA said. Typically an extremely worn chain is one that is gone beyond 0.75% stretch, and if you consider that a normal chain is in or around 114-116 links long out-of-the-box, the new chain is approx 57-58 inches (each pair of links being an inch). That means that a stretched chain (assuming you use the full length, which would be rare!) is about 57.43" or 58.44" long, i.e. less than an extra 1/2" for the whole chain, and realistically even less, since most chains get cut shorter. Given that a single inner or outer link is 1/2", comparing old and new should be accurate to a reasonably high degree :)


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