Putting road double on a MTB

venster
venster Posts: 356
edited June 2007 in Workshop
I've successfully fitted my old road double chainset to my MTB. Everything shifts nicely apart from the front mech - which rubs. I now know I need a double for the front - my question is

Can I use a normal road bike double for the front ? Or does it have to be a MTB one (if they do one).

Doesn't have to be pretty - it's just my bike for going around the streets with my kids.

Comments

  • Pirahna
    Pirahna Posts: 1,315
    I've used road chainsets on mountain bikes in the past without problem. I've use MTB front mechs but they've been for full size MTB chainsets with a 46 outer ring, not compacts.

    Maybe the mech just needs a bit of tweaking.
  • monty_dogcp
    monty_dogcp Posts: 382
    It depends on the chainline and whether you've fitted a road BB too - fitting a double chainset to a triple BB means that the chainrings can sit too far out for a road front mech to swing out far enough. Trouble is that sometimes fitting the narrower road BB often means than the inside chainring fouls the chainstay! I've usually ended up using an MTB front mech and just limiting the movement with the stop screws. I've used a 'compact' Deore front mech quite successfully with a 53 tooth chainring
  • maddog_2cp
    maddog_2cp Posts: 73
    road and mtb front mechs aren't the same, in terms of cable pull.

    the upshot of this is that the easiest solution is to use an mtb mech if possible.

    have a look on ebay for an older, non-compact mech such as a DX, XT or XTR mech which was designed to handle 46t outer rings (or 48t for the XTR)

    Note: check the band size (28.6, 31.8 or 34.9) and whether it's top or bottom pull



    However, a road front mech can work with a mtb shifter, with a little tweaking. Here's how:

    1. Set the mech up so that click 3 (on the shifter) is correct for the big ring

    when you shift down to the smaller ring the road mech will over-shift. To stop this..

    2. set the limit screw to stop the mech over-shifting on click 2

    Click 1 is now redundant. If you click down to click 1 the cable will just go slack, but the mech won't move as the limit screw is holding it in the correct position for the smaller ring.



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  • venster
    venster Posts: 356
    Oh right - I might not have it set up correctly.

    I'm using the MTB front mech, but am using it on clicks 1&2 - I suppose I could try 2&3 because in effect, I've got rid of the granny ring haven't I.

    Oh, it got the road BB too, not MTB.

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