-0.20%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 245/40R20, fitting 275/40R19 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 39.9 km/h | 25 mph | 25 mph |
| 60 km/h | 59.9 km/h | 37 mph | 37 mph |
| 80 km/h | 79.8 km/h | 50 mph | 50 mph |
| 100 km/h | 99.8 km/h | 62 mph | 62 mph |
| 120 km/h | 119.8 km/h | 75 mph | 74 mph |
Full comparison
245/40R20
Overall diameter704.0 mm · 27.72 in
Section width245 mm · 9.65 in
Sidewall height98.0 mm · 3.86 in
Circumference2211.7 mm · 87.1 in
Revolutions per mile728
Revolutions per km452
275/40R19
Overall diameter702.6 mm · 27.66 in
Section width275 mm · 10.83 in
Sidewall height110.0 mm · 4.33 in
Circumference2207.3 mm · 86.9 in
Revolutions per mile729
Revolutions per km453
-0.2%Safe swap — speedometer error is minor
Original
Overall diameter704 mm · 27.72 in
Sidewall height98 mm
Circumference2,211.7 mm
Revolutions / mile727.7
New
Overall diameter702.6 mm · 27.66 in
Sidewall height110 mm
Circumference2,207.3 mm
Revolutions / mile729.1
Speedometer & odometer error
The new tire changes overall diameter by -0.2%. 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 | 39.9 km/h | 25 mph | 25 mph |
| 60 km/h | 59.9 km/h | 37 mph | 37 mph |
| 80 km/h | 79.8 km/h | 50 mph | 50 mph |
| 100 km/h | 99.8 km/h | 62 mph | 62 mph |
| 120 km/h | 119.8 km/h | 75 mph | 74 mph |
See individual specs: 245/40R20 · 275/40R19. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.