Size Ply Diameter Width Rim Width PSI Load 18X7.0 R-7 2 18.0 6.7 5.50 3 112 19X8.0 R-7 2 18.9 7.9 6.50 3 130 20X7.0 R-8 2 19.7 6.6 5.50 7 220 21X7.0 R-10 2 20.8 6.5 5.50 4 190 22X8.0 R-10 2 21.9 7.3 6.00 3 180