Originally Posted by
Scrodzilla
Not really.
Not sure what the "light-bulb effect" is, but wider rims will spread out a tire regardless of the tire width. A 2.1" mtb tire mounted to a narrow mtb rim will have a narrower, taller profile than the same tire mounted to a wide mtb rim. On a mtb or cx bike, this allows you to run lower pressure without the tire wanting to roll over when you corner on it aggressively, and this in turn, improved the ride quality. The same tires ride better on A23s than they did on Open Pros. My mtbs all have wide rims, around 25+mm.