I don't like to have tires mounted that are only as wide as the rim's outside width is. Tires with a slight curve to the sidewall (between the rim and tread cap) ride nicer IMO. But too much curve (or overhang) and the tire bead will more easily come un seated in extreme side loading, the side wall can wear more right at the rim's top edge and the handling tends to be a bit more "wallowy".


But their are no black and whites in this discussion, only shades of gray and opinions. this is why we often suggest experimenting and finding out your real results.


When going to a wider tire be aware of tire/frame/fork/caliper/fender/rack clearances. When going to a narrower tire pay attention to pedal/ground strike increase. Andy