Rim - Optimum tire size

4.5" - 160\60
5" - 170\60
5.5" - 180\55
6" - 190\50,55

In the very least, these are the tire choices made by the engineers from each manufacturer when deciding the rim size. Now I know that a 170/60 fits on a 5.5" rim & a 180/55 fits a 6" rim, but I never seen them come that way from the manufacturer.