My bike came with 2.125 width tires, and the chain would rub the tire. I went down to 1.95, and the chain doesn't rub anymore. I wouldn't go any smaller than 1.95, because the smaller the tire width, the more you feel the vibrations from the road, and bumps and whatnot. Just my opinion, though. If you feel comfortable running 1.5, go ahead. But I think 1.95 should give you plenty of clearance with the chains.