Originally Posted by
jamal
Just a reminder that weight and pressure determine contact patch area. I don't think a slight change in diameter you would see from, say the next size up or down that would still work on the same vehicle is going to have much of an effect on shape though. Clearly, if I make my tire 20mm narrower, the patch will need to be 20mm longer. But what change would I see from going like 1/2" shorter in diameter?
In addition to a narrower tread having some benefit in looser stuff, deep snow, slush (rally cars us hilariously narrow tires in the winter btw), the other part if it has to do with what's called slip angle. When you corner, there's a difference between where the wheel is pointed and where the car is actually going. Part of this slip angle comes from deflection of the tire casing, some comes from deflection of the tread, and some comes from parts of the tread slipping in relation to the road. More slip angle, more cornering force, more cornering force, more slip angle. On pavement, a lower slip angle is preferable, so low profile, wide, stiff tires. Makes the car more responsive and keeps tire temps lower. On ice and snow and low grip situations however, softer, taller, narrower tires mean higher slip angles and more feedback to what's happening between the tire and the road before you are fully sliding out of control.
The downside there being more floating and squirming around on the dry pavement but you get used to that and it works better in the snow.