Chainring problem after new chain

sjclark
sjclark Posts: 64
edited April 2008 in Workshop
I have a Shimano Tiagra 9sp Compact drivetrain. I recently replaced the old SRAM chain with a new one and also replaced the cassette with a 9sp SRAM one.

This worked fine on my first proper ride but has now started skipping on the small chainring and occasionally coming off. This only happens when I put significant force through the pedals (such as if I stand up). If I am pedalling smoothly it is fine. It behaves completely fine on the larger chainring.

Any ideas as to what is causing this?

Do I need a new chainring? Is the chain too long? Is the rear mech not putting enough tension on the chain so needs replacing (it is 2500 winter miles old)?

Thanks in advance.

Steve

Comments

  • rdaviesb
    rdaviesb Posts: 566
    Depends how much cack you normally have on your chain, but I wouldn't have thought you'd have worn the chainring out. Are you sure it's not bent?
  • sjclark
    sjclark Posts: 64
    Having now shortened the chain slightly (in line with the Shimano instructions for the rear mech), the problem seems to have reduced.

    Makes me think it is the rear mech's tension.

    Does this sound sensible? If so, is it a new rear mech? Will the B-Adjustment screw help?

    Thanks
  • Stuck on a Giant
    Stuck on a Giant Posts: 256
    I had a similar problem on my MTB even after I'd changed the casssette. I ordered a new set of chainrings but before fitting them I gave the chain and existing chainrings a good clean and they're been fine ever since, so I haven't needed to change the rings.

    Wear on the chainrings is usually fairly visible, with a 'shark's fin' profile developing. You also tend to get chain-suck on worn rings.

    You might be right about chain tension, but if it was working fine before you made the changes, it should still be OK.

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