I think you need to look at these tire and rim combinations. A narrow rim might cause an over size tire to assume an odd shape. Also if the tire has a tread pattern you might be forcing it open and riding on exposed inner edges. The opposite is probably also true with a narrow tire mounted to a wide rim you will end up using the side wall Jan has spent considerable time testing tires and I am not sure if any of it involved this topic. I know on wider tires for those off topic bikes , tire design is such that a ''Fat tire'' has a specific sidewall shape
BOB FREITAS where off topic bikes are fun to ride in the bad weather here in
MILL VALLEY, CA USA