Is my chain too long?

carl_p
carl_p Posts: 989
edited July 2009 in Workshop
I'm trying to fit a new chain to a frame I'm building up so I don't have an old chain to compare it against. I estimated the required chain length by wrapping it around the large chain ring and largest rear cog, but not through the derailleur and then added 2 links to this measurement. I double checked this using the formula on Park Tools website and it seemed to agree.

Having reduced the length and threaded it through the rear derailleur and joined the ends it seems ok on most of the gearing options except on the smallest chain ring and smallest cog where it hits the chainstay. It really does look loose and I can foresee it dropping off . I would point out I haven't installed the cable yet and have set the derailleur H and L limits without cable tension. I'm using a medium cage mech with standard double 53/39 and 12/25 cassette.

Should I be taking a couple more links out or is there something else I should be looking at? Do you think I should try a short cage rear mech?
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Comments

  • Mister W
    Mister W Posts: 791
    I would normally add only 1 link but the key thing is that the chain is long enough to get onto the big ring and the biggest cog. The small ring and smallest cog is a combination you're unlikely to be using so don't worry too much if the chain is a bit slack.
  • carl_p
    carl_p Posts: 989
    I don't think one link would make much difference.

    Interestingly it's a second hand frame and there is considerable scuffing on the carbon chainstay guard which suggests the previous owner had similar issues. When I turn the cranks it seems to take up the slack and is just about ok, but with no pressure on the crank it seems very loose.
    Specialized Venge S Works
    Cannondale Synapse
    Enigma Etape
    Genesis Flyer Single Speed


    Turn the corner, rub my eyes and hope the world will last...
  • Mister W
    Mister W Posts: 791
    You'd be suprised how much difference one link will make. Having said that, with those chainrings and cassette and a medium cage mech you shouldn't be having problems. I ride a compact chainset with an 11-23 and a short cage mech and the chain is fine. Maybe the mech isn't working properly. Are the springs pulling it back as far as it can go?
  • carl_p
    carl_p Posts: 989
    Mister W wrote:
    You'd be suprised how much difference one link will make. Having said that, with those chainrings and cassette and a medium cage mech you shouldn't be having problems. I ride a compact chainset with an 11-23 and a short cage mech and the chain is fine. Maybe the mech isn't working properly. Are the springs pulling it back as far as it can go?

    Cheers Mister W.

    Right I've reinstalled the mech, this time properly (I hope), first time round I failed to line up the B limit screw with the tab on the gear hanger hence it was in the wrong place :oops: .

    Have taken another link out and no sag now :lol: bordering on the too tight :roll:
    Specialized Venge S Works
    Cannondale Synapse
    Enigma Etape
    Genesis Flyer Single Speed


    Turn the corner, rub my eyes and hope the world will last...