The new tire changes overall diameter by -8.15%. 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 | 36.7 km/h | 25 mph | 23 mph |
| 60 km/h | 55.1 km/h | 37 mph | 34 mph |
| 80 km/h | 73.5 km/h | 50 mph | 46 mph |
| 100 km/h | 91.9 km/h | 62 mph | 57 mph |
| 120 km/h | 110.2 km/h | 75 mph | 68 mph |
Commonly compared with 275/40R20
- 275/40R20 vs 245/45R20 · 245/45R20 specs
- 275/40R20 vs 265/40R20 · 265/40R20 specs
- 275/40R20 vs 255/45R20 · 255/45R20 specs
- 275/40R20 vs 255/50R19 · 255/50R19 specs
- 275/40R20 vs 285/45R19 · 285/45R19 specs
- 275/40R20 vs 295/35R21 · 295/35R21 specs
- 275/40R20 vs 235/55R19 · 235/55R19 specs
- 275/40R20 vs 295/40R20 · 295/40R20 specs
FAQ
What is the overall diameter of a 275/40R20 tire?
A 275/40R20 tire has an overall diameter of about 28.66 inches (728 mm) and a section width of 275 mm.
What sizes can replace a 275/40R20 tire?
Sizes within about ±3% of 275/40R20's 28.7-inch diameter are the closest matches, such as 245/45R20, 265/40R20, 255/45R20. 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.