The front mech on my MTB race bike needs replacing, and looking at weightweenies, Shimano front road mechs seem to be lighter than equivalent MTB mechs. Can I fit a road front mech? I need a triple, 34.9 band on bottom pull mech, so am thinking a DuraAce or Ultegra mech of the right type will be OK. Anyone done it? What’s the downside?

The pull ratio is a bit difference and they’re designed to work with different chainring sizes to mtb. You may be able to bodge it to kind of work but it will never be perfect.

If you’re running a double, then an old friction shifter thumbie will work just the same. Would work with a triple too, but of course un-indexed.

APF

Waste of time. Save 5gm for a lifetime of faff and crap shifting.

What’s more important – the few grams, or being able to hit the big ring quickly and smoothly when you need to?
A road FD generally won’t do that on an MTB triple with a 50mm chainline.

It is the chainline that will probably be the issue. With an mtb chainset the road mech probably won’t swing out far enough to get to the big ring. Or if it does the chain will rub on the bottom of the cassette.

Plus as mentioned the cable pull is different (unless it Sram 2×10).

Twaddle. Had a shimano braze on road FD (cant remember the model) on my old maverick ml7 and had years of faultless shifting.

I’ve an xtr front mech that might fit as I’m looking for a band on 34.9 if that’s any easier, email in profile.

Trailhound, with what chainset? Octalink and square taper c’sets were narrower chainline than external BB c’sets, road FDs worked ok with them.

HT2 BB and XT chainset 22 32 44