Mountain bikes now go down to about 18 inches with a 34T single chain ring and a 50T large sprocket. The problem is the huge jumps between the sprockets that go from 10-50 with 12 speeds. On the road, it would feel like you're always in the wrong gear because the right one if in-between two sprockets.
Even shimano's 11-34 11 speed cassette has big jumps of 11-13-15-17...
Last edited by DaveSSS; 10-20-19 at 12:47 PM.