which front mech?

Bob the dog
Bob the dog Posts: 42
edited August 2007 in Workshop
Is there any reason why a mountain bike mech won't work with a road bike crank? I've got a Sora 52T crank and a Sora front mech, however the cabling is for top-pull, so I've used a travel adapter. I was going to replace this with an LX mountain bike mech, which is top-pull and I wouldn't need the travel adapter. Bearing in mind a MB crank would have less teeth, would this work?

Comments

  • nicklouse
    nicklouse Posts: 50,675
    nope.too many teeth.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Monty Dog
    Monty Dog Posts: 20,614
    There probably isn't enough clearance between the seat tube and the wheel to allow it to fit on a road frame - but if it does, it'll work OK - I used a regular Deore MTB mech with a 53 teeth chainring a few years ago on an MTB frame converted to road use
    Make mine an Italian, with Campagnolo on the side..
  • leonlikestrees
    leonlikestrees Posts: 528
    I have the same problem on my cross bike.

    This is what I discovered:

    - Road STI's pull different amounts of cable to MTB ones. If you are using a double chainset, it's fine, but it'sdifficult to get decent indexing on a road triple with an MTB mech

    - MTB mechs aren't designed for small gaps between the chainrings - running a 38/48 combo with an MTB front mech didn't work well as I had to nstall it too high so that the inner plate would not hit the inner chainring. Running 38/50 is fine though

    I've just ended up with one of those adpaters. It's possible to get an MTB mech to work, but it's simpler to use a road one with the adpator, and works better (IMO). I just wish Shimano would make a top pull road mech. Ive scoured the catalogues and they don't even make one for city bikes.

    More to the point, I wish my frame designer had done as much research as I had when he was deciding how to route the front mech cable.
  • Bob the dog
    Bob the dog Posts: 42
    This is turning into a major pain in the butt, I'm sure there ought to be a simple solution.
  • leonlikestrees
    leonlikestrees Posts: 528
    i couldn't find one. I think the little pully wheel is the simple solution :-(

    If you have a steel frame, you could get the cable routing changed, but then you'd need a respray.

    what bike is it, and what chainrings do you have?

    If you have a 39 inner, and it's not a triple, you'll probably be fine with an MTB mech, however you still need to make sure you get one with a large tooth capacity, but even then it might not work:

    this one is designed for a 48t big ring:

    http://www.chainreactioncycles.com/Models.aspx?ModelID=19205

    It would probabl work, but I wouldn't like to say for sure without actually trying it.
  • aracer
    aracer Posts: 1,649
    You could always mod your road mech to top pull...

    http://weightweenies.starbike.com/phpBB ... hp?t=30725

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