Originally Posted by
Jipe
Indeed, the narrow rim changes the tire profile to a round shape.
If the rim is really narrow, this round shape only rest on the rim on a small part of the round and when cornering, there is big lateral tire shape deformation (the tire is pushed on one side of the rim) which is even bigger if the tire pressure is low.
That is true. There's also more of a bending angle between the tire bead and the sidewall (even when just rolling straight), which can prematurely fatigue that area.
Some things may not be hard rules, but still, "best practices".