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Front derailleur chain line?

  • 06-06-2011 11:25am
    #1
    BillieBob
    Registered Users, Registered Users 2 Posts: 91 ✭✭


    Hey,

    I replaced my bottom bracket from a sis to a hollowtech Deore upgrade. The bottom bracket on the frame was 68mm so I included all 3 of the spacers that came with the new bottom bracket. All good with the bottom bracket, the only problem now is that the front derailleur (SIS one) is now rubbing the chain on the new front cogs. It seems that the chainline is off now. I tried to mess with the adjustment screws on the front derailleur but they didn't seem to do much. Before I put on the new bottom bracket I would have thought that all front derailleurs have a standard chainline and are interchangeable.

    So, do I need to upgrade the front derailleur to Deore as well as the bottom bracket to get the chainline right? It doesn't seem to me that I can adjust the existing sis front derailleur to work. All advice welcome, thanks.


Comments

  • #2
    bcmf
    Closed Accounts Posts: 6,679 ✭✭✭bcmf


    Is it rubbing in all the gears? Rubbing the outer plate of the fd or the inner plate?
    May do no harm to reset the fd.


  • #3
    kona
    Registered Users, Registered Users 2 Posts: 7,525 ✭✭✭kona


    What order are the spacers. AFAIK its 2 on the driveside and 1 on the left side for 68mm BB shells It will say in the manual.

    Dont go messing with the limit screws either, they dont adjust the Derailleur, the cable tension does.


  • #4
    Holyboy
    Registered Users, Registered Users 2 Posts: 869 ✭✭✭Holyboy


    If it's a basic Shimano front mech it's probably designed for a 42 tooth outer chainring but your Deore chainset will have a 44 tooth outer ring, if this is the case you should really replace the front mech, but you should be able to get the one you have to work to some degree it might not shift perfect though!
    If the old chainset was 42tooth outer you'll have to move the whole mech up a bit before doing any thing else,have a look on Shimanos' website or even Sheldon Browns site for tips on adjusting a front mech.
    Oh and your BB shell should have been faced before fitting the out board bearings!!!!


  • #5
    BillieBob
    Registered Users, Registered Users 2 Posts: 91 ✭✭BillieBob


    It's rubbing the outer plate of the fd in 4 or 5 of the rear cogs, only when on the really easy cogs that it doesn't rub. I'll check what no. of teeth were on the old chainset, and I'll also check the spacers tho' I'm pretty sure that I put them on as per the instructions. As for facing the bb, Youtube didn't say anything about that....


  • #6
    ashleey
    Registered Users, Registered Users 2 Posts: 2,005 ✭✭✭ashleey


    The park tools website has excellent tutorials too if that helps


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  • #7
    kona
    Registered Users, Registered Users 2 Posts: 7,525 ✭✭✭kona


    BillieBob wrote: »
    It's rubbing the outer plate of the fd in 4 or 5 of the rear cogs, only when on the really easy cogs that it doesn't rub. I'll check what no. of teeth were on the old chainset, and I'll also check the spacers tho' I'm pretty sure that I put them on as per the instructions.

    Are you sure your chainset has more teeth than standard? Anytime Ive fitted a larger cog the front mech has to be moved up and it Barely clears the chainset. Also the chainlength can be a pain in the balls too.

    just a obvious one too, make sure your in top on the shifter and not the middle. when you shift up, theres a little kind of trim on shimano shifters to allow the chain not to rub on the last few gears.
    BillieBob wrote: »
    As for facing the bb, Youtube didn't say anything about that....

    A professional job would include facing the BB and if you have disc brakes, the disc mounts. It ensures the bearings sit flat against the BB shell, if there is paint its hard to achieve this.


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