The new tire changes overall diameter by -5.01%. With a speedometer calibrated to the original tire, that same percentage is how far the speedometer and odometer read off — a taller tire means your true speed is higher than indicated and the odometer under-counts distance.
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 38 km/h | 25 mph | 24 mph |
| 60 km/h | 57 km/h | 37 mph | 35 mph |
| 80 km/h | 76 km/h | 50 mph | 47 mph |
| 100 km/h | 95 km/h | 62 mph | 59 mph |
| 120 km/h | 114 km/h | 75 mph | 71 mph |
Commonly compared with 245/40R20
- 245/40R20 vs 245/45R19 · 245/45R19 specs
- 245/40R20 vs 275/40R19 · 275/40R19 specs
- 245/40R20 vs 265/40R20 · 265/40R20 specs
- 245/40R20 vs 255/40R19 · 255/40R19 specs
- 245/40R20 vs 275/40R20 · 275/40R20 specs
- 245/40R20 vs 245/45R20 · 245/45R20 specs
- 245/40R20 vs 245/40R19 · 245/40R19 specs
- 245/40R20 vs 235/40R19 · 235/40R19 specs
FAQ
What is the overall diameter of a 245/40R20 tire?
A 245/40R20 tire has an overall diameter of about 27.72 inches (704 mm) and a section width of 245 mm.
What sizes can replace a 245/40R20 tire?
Sizes within about ±3% of 245/40R20's 27.7-inch diameter are the closest matches, such as 245/45R19, 275/40R19, 265/40R20. Use the calculator above to check the exact speedometer effect of any substitute.
Fitment & trouble codes
Changing tire size by more than about 3% shifts the speedometer, odometer and, on some vehicles, ABS/traction calibration — which can set wheel-speed-sensor or vehicle-speed codes. See C1234 (wheel speed sensor) and C0050 (rear wheel speed) if a warning light appears after a size change.