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On going chain problems

dell14789dell14789 Posts: 4
edited October 2017 in Workshop
Other than my road bike having a ghost or my bike being sabotaged while left at work I and my local lbs have run out of ideas while I am getting this issue . I keep constantly having issues with chain coming off!! Had no problems until I had bike serviced ( not been to that lbs since) . Gear is changing fine then suddenly just throws off the chain. Initially was always on inside but now is coming off to the right on big ring. Each time has come off I have either got sorted road side myself, a friend has sorted or taken to local lbs. Has been in perfect working order then goes again. The chain and cassette is quite new and both are fine, derailleur looks fine, new cables. LBS were so fed up last time they stripped bike down for me and did a full check, they assured me it was 100% spot on. I rode straight from there to work( 1 mile). After work rode 3 minutes down road, tried to change into big ring and chain came off again. I did wonder if I was somehow catching cage with my heel when riding or unclipping but last few rides have got someone to watch and I amnowhere near. I having been riding many years ( qualified cycling coach)so am changing gear correctly. There is just no reason I or lbs can come up with other than someone is messing with it while is in bike store at work. Any other thoughts.

Posts

  • The RookieThe Rookie Posts: 27,748
    Front mech alignment (height and/or toe angle) or indexing, the chainrings are designed to throw the chain off to ease shifting, its the front mech that keeps it in place. the fact its gone from falling off the inside to falling off the outside is down to a change in indexing.

    If the LBS can't figure that out I wouldn't be using them.
  • imposter2.0imposter2.0 Posts: 11,402
    As above. Also, did anyone mention limit screws? If it's falling off the inside or outside, that would be one of the first things I would look at.
  • jgsijgsi Posts: 5,031
    You sound a candidate for one of the fugly 1x setups.... however failing that
    find a better spanner man
    bite the bullet and setup yourself
    In simple terms, if the chain is being thrown too far out or in , it will come off the ring.
    Thus, the use of those limit screws is vital , as is the correct amount of tension on the shifter cable itself.
  • jgsijgsi Posts: 5,031
    +
    put the bike on the turbo.
    Stand over the top tube and looking down take 1 picture of the front mech, at rest, small chainring
    then another with the shifter engaged , so chain is on the large chainring.
  • Will do as suggested by JGSI and have a good luck. LBS I have taken it to are well regarded and several of my friends use them and have done for many years. They are adamant indexing is perfect when it leaves them. Am seriously thinking my comment in jest about bike being messed with might actually be what is happening. Just spoken to one of the other lads who works here and he has said he is getting very odd mechanical issues , low air in tyres etcetra when he gets bike to ride home!!!
  • Is it only doing it under load?
    If it's a new chain and cassette it could be worn chain rings. I had exactly this issue after fitting a new chain, and a new cassette didn't fix it. The big ring teeth looked fine, but were worn enough that under load the chain wouldn't mesh properly and rise up the teeth and slip off ... some times it would be to the inside, sometimes to the outside, just depended what rear gear I was in (i.e. chain-line).

    Do you have a picture of your outer chain-ring ?
  • dell14789 wrote:
    dell14789 wrote:
    it was 100% spot on. I rode straight from there to work( 1 mile). After work rode 3 minutes down road, tried to change into big ring and chain came off again. There is just no reason I or lbs can come up with other than someone is messing with it while is in bike store at work. Any other thoughts.

    Just spoken to one of the other lads who works here and he has said he is getting very odd mechanical issues , low air in tyres etcetra when he gets bike to ride home!!!
    Sounds like a possibility.
  • The cage may be distorted after throwing the chain, after that it is very difficult to get it right again.
    Check the inside of the outer plate on the cage, it should NOT bow out.
    Check it is parallel to the ring.
    Check the limit screws are set correctly.
    Read the instructions for settin git up on the manufacturers website (shimano, sram, campagnolo, whatever).

    Why are you shifting it out of the big ring in the first place?
  • Sorted.

    Sad to say someone messing with the bikes . Caught red handed letting air out of one of my colleagues tyres. Has admitted to various things over the last couple of months. As you would expect is now looking for a job. T
  • Glad you found out what (or who as it turns out) was causing the problem.
    What a complete bell-end.
    Not sure I'd be able to restrain myself if I discovered someone tampering with my, or a colleagues, bike.
    Nice to see that management took it seriously enough and handed them their P45 - I guess they're lucky it wasn't the police, as tampering with someones bike can have nasty (and potentially fatal) consequences.
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