Chain rubbing on front mech

GavH
GavH Posts: 933
edited January 2009 in Workshop
Just replaced my old square-taper BB and 50/36 cranks with a Shimano 105 HTII BB and Tiagra 50/34 chainset.

When I've got the chain on the 34T and the biggest sprockets at the back (top 3 of 8) the chain is rubbing heavily against the inside of the front mech. Needless to say it WASN'T doing this previously. I've adjusted the L screw as much as I can to no avail so am now stuck for solutions?

Can anyone suggest what needs to be done please?

Comments

  • whyamihere
    whyamihere Posts: 7,719
    The BB on the new cranks will be shorter than your old one. You were right to adjust the L screw, and my guess would be that the cable tension is preventing the mech from moving to its new limit. I would release the cable, adjust the limit screw to the right position and then pull the cable tight and refasten it, checking that you have enough tension to shift smoothly. You will also need to adjust the high tension screw as the outer chainring will have moved inwards as well.
  • GavH
    GavH Posts: 933
    Many Thanks, I'll give that a go and see how it goes.
  • GavH
    GavH Posts: 933
    whyamihere wrote:
    The BB on the new cranks will be shorter than your old one. You were right to adjust the L screw, and my guess would be that the cable tension is preventing the mech from moving to its new limit. I would release the cable, adjust the limit screw to the right position and then pull the cable tight and refasten it, checking that you have enough tension to shift smoothly. You will also need to adjust the high tension screw as the outer chainring will have moved inwards as well.

    Done as above and all well now - Thanks very much! :D

    Loving this site, learning something new almost every day!

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