SRAM + chain length

gloomyandy
gloomyandy Posts: 520
edited January 2013 in Workshop
Hi,
In the process of building a new bike using SRAM shifters/mechs etc. The guide for chain length from SRAM says: put the chain on big/big (not via the rear mech), make a note of the chain length when pulled tight and add one complete link (one inner + one outer).

Pretty simple you might think. The thing is SRAM/KMC chains use a quick link so you need both ends to have an inner, when I measure the chain it meets at the outer point. So I can either add half a link or one and a half links. If I add one and half links then when in small chain ring and either of the two smallest rear cogs the chain rubs against the rear mech arm as it returns (the arm is curled right back), if I add half a link then when on big, big the chain runs very roughly, jumping etc (when using the longer chain it is fine in this combination so not a simple alignment issue).

I realize the using either small/small or big/big is not a good idea, but I'd like to get things as good as I can. Anyone got a recommendation as which is best and if there are any other adjustments I could make to the setup to make either of the options work better?

Thanks

Andy

Comments

  • sungod
    sungod Posts: 16,845
    the chain must *not* rub on the arm of the rear mech, so whatever length chain does that is wrong

    noisy chain probably means the rear mech needs adjusting, not simply the barrel adjuster, but the b screw, this can make a big difference to how the chain meshes with the cassette
    my bike - faster than god's and twice as shiny