Front Mech advice

jonrb101
jonrb101 Posts: 86
edited March 2011 in MTB workshop & tech
I'm building a light, rigid MTB for fast road use only and want to run it with a stronglight 48/38/28 chainset. I have SRAM X9 shifters and rear mech, but the X9 front mech states max teeth of 44. I've not got the front mech yet and want to make sure I buy the right one - will a standard X9 work with 48 tooth? or can you recommend a suitable alternative please?
I've tried an old LX mech I have, but I think this is not compatible with SRAM shifters (wrong cable pull). I need 34.9mm top pull.

Cheers

Jon

Comments

  • nicklouse
    nicklouse Posts: 50,675
    your LX front mech will work.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jonrb101
    jonrb101 Posts: 86
    Already tried it and it doesn't!
  • The Rookie
    The Rookie Posts: 27,812
    OK, "it will work properly if properly set up", that better?

    SRAM and shimano cable pull are the same for the front mech, so its not that.

    What issue do you have?

    Simon
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • jonrb101
    jonrb101 Posts: 86
    Sorry for the delay guys - I've done some more checking and the problem is more to do with chainline. To get clearance for the bigger rings against the chainstay, I've had to go for a longer bb (118mm), this has put the chainline to 54mm and the LX front mech won't swing that far across, it's designed for a 50mm chainline. Looks like I will have to go for a standard MTB chainset, or are there any front mechs that will swing further out? Any further advice appreciated. Cheers
  • nicklouse
    nicklouse Posts: 50,675
    nope there is nothing out there for such a wide chain line.

    did you really need to use a 118mm axle?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jonrb101
    jonrb101 Posts: 86
    With a 110mm axle, the outer chainrings are tight against the chainstay. The only other option in 73mm shell is 113mm (I think) and I don't think that it will give much more (sufficient) clearance. Cheers. Jon
  • nicklouse
    nicklouse Posts: 50,675
    what is the crankset?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jonrb101
    jonrb101 Posts: 86
    It's a Stronglight - don't know thw mode, but will check tonight. Cheers
  • nicklouse
    nicklouse Posts: 50,675
    square taper fitting?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jonrb101
    jonrb101 Posts: 86
    Yes, square taper.
  • nicklouse
    nicklouse Posts: 50,675
    i would be looking at a 113 or a 115 axle length.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jonrb101
    jonrb101 Posts: 86
    This could become expensive if it's trial and error!

    I presume a 115 will move the chainline in by 1.5mm from the 118 and a 113 by 2.5mm?
  • nicklouse
    nicklouse Posts: 50,675
    well.
    http://www.sheldonbrown.com/bbsize.html

    but BB from just under a tenner on CRC (use paypal ;) ) and return what aint needed?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • jonrb101
    jonrb101 Posts: 86
    Sounds like a plan - Cheers

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