[Myron Piatek]

A wider rim will allow more air pressure while maintaining a fuller/wider "footprint" over a narrower rim. A tire will also grow less at speed with a wider rim. Higher air pressure also reduces sidewall "wrinkle", which helps it last longer and can help the car be more stable at the top end.

A wider rim will increase the section width a bit.

Each car/combo should still be tested to see what air pressures will work the best because of the many variable.

On the same rim, a radial slick will grow less than a bias ply because of their construction. So you may have to adjust your gear ratio accordingly. But radials aren't normally recommended for stick cars.