I am about to purchase a stem labeled "Mountain Stem" with the two diameters:
- 1-1/8" steerer
- 31.8mm bar clamp
to install on a road bike. There is stock of "road bike stems", but of considerably longer lengths (generally 60mm to 110mm). I'm adapting an XS adult road bike for a child's reach. (I wish it had 650 wheels, not 700, but that's a separate issue.)
Is there any reason why an MTB stem would not work on a road bike? What makes a stem a "mountain stem"? Will it be ("just") heavier/more rugged than necessary?
From the bike's specs sheet, I know the steerer is 1-1/8", but I am not certain that the bar clamp is 31.8mm and not 30.9mm. My impression is that it is only with seatposts that one can end up with this nasty little surprise of confusing 31.8mm and 30.9mm, and that adult bike handlebars are 31.8mm, but are not made in the 30.9mm diameter; can you confirm?