Tire Size Finder (optional):
Stock Sizes
- 255/75-16
Plus Sizes
- 255/75-16
Accepts P-Metric and Inches
| 305/30-21 | 305/20-21 | Difference | |
|---|---|---|---|
| Diameter inches (mm) | 28.2 (716.4) | 25.8 (655.4) | -2.4 (-61) -8.5% |
| Width inches (mm) | 12.01 (305) | 12.01 (305) | 0 (0) 0% |
| Circum. inches (mm) | 88.61 (2250.64) | 81.06 (2059) | -7.54 (-191.64) -8.5% |
| Sidewall Height inches (mm) | 3.6 (91.5) | 2.4 (61) | -1.2 (-30.5) -33.3% |
| Revolutions per mile (km) | 715.06 (444.32) | 781.61 (485.67) | 66.55 (41.35) 9.3% |
Speedometer Difference
| Speedo Reading | Actual Speed |
|---|---|
| 20 mph (32.19 km/h) | 18.3 mph (29.45 km/h) |
| 25 mph (40.23 km/h) | 22.87 mph (36.81 km/h) |
| 30 mph (48.28 km/h) | 27.45 mph (44.17 km/h) |
| 35 mph (56.33 km/h) | 32.02 mph (51.53 km/h) |
| 40 mph (64.37 km/h) | 36.59 mph (58.89 km/h) |
| 45 mph (72.42 km/h) | 41.17 mph (66.25 km/h) |
| 50 mph (80.47 km/h) | 45.74 mph (73.62 km/h) |
| 55 mph (88.51 km/h) | 50.32 mph (80.98 km/h) |
| 60 mph (96.56 km/h) | 54.89 mph (88.34 km/h) |
| 65 mph (104.61 km/h) | 59.47 mph (95.7 km/h) |
| 70 mph (112.65 km/h) | 64.04 mph (103.06 km/h) |
| 75 mph (120.7 km/h) | 68.61 mph (110.42 km/h) |
| 80 mph (128.75 km/h) | 73.19 mph (117.79 km/h) |
| 85 mph (136.79 km/h) | 77.76 mph (125.15 km/h) |
| 90 mph (144.84 km/h) | 82.34 mph (132.51 km/h) |
| 95 mph (152.89 km/h) | 86.91 mph (139.87 km/h) |
| 100 mph (160.93 km/h) | 91.49 mph (147.23 km/h) |
| 2.35 | 2.73 | 2.94 | 3.07 | 3.21 | 3.31 | 3.42 | 3.55 | 3.73 | 3.91 | 4.11 | 4.27 | 4.56 | 4.88 | 5.13 | 5.29 | 5.38 | 5.71 | 6.17 | 7.17 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1989 | 2311 | 2488 | 2598 | 2717 | 2802 | 2895 | 3005 | 3157 | 3309 | 3479 | 3614 | 3860 | 4130 | 4342 | 4477 | 4554 | 4833 | 5222 | 6069 |
Better Fuel Economy Factory Ratios Increased Power
