-1.58%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 245/50R20, fitting 235/55R19 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 39.4 km/h | 25 mph | 24 mph |
| 60 km/h | 59.1 km/h | 37 mph | 37 mph |
| 80 km/h | 78.7 km/h | 50 mph | 49 mph |
| 100 km/h | 98.4 km/h | 62 mph | 61 mph |
| 120 km/h | 118.1 km/h | 75 mph | 73 mph |
Full comparison
245/50R20
Overall diameter753.0 mm · 29.65 in
Section width245 mm · 9.65 in
Sidewall height122.5 mm · 4.82 in
Circumference2365.6 mm · 93.1 in
Revolutions per mile680
Revolutions per km423
235/55R19
Overall diameter741.1 mm · 29.18 in
Section width235 mm · 9.25 in
Sidewall height129.3 mm · 5.09 in
Circumference2328.2 mm · 91.7 in
Revolutions per mile691
Revolutions per km430
-1.58%Safe swap — speedometer error is minor
Original
Overall diameter753 mm · 29.65 in
Sidewall height122.5 mm
Circumference2,365.6 mm
Revolutions / mile680.3
New
Overall diameter741.1 mm · 29.18 in
Sidewall height129.3 mm
Circumference2,328.2 mm
Revolutions / mile691.2
Speedometer & odometer error
The new tire changes overall diameter by -1.58%. 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 | 39.4 km/h | 25 mph | 24 mph |
| 60 km/h | 59.1 km/h | 37 mph | 37 mph |
| 80 km/h | 78.7 km/h | 50 mph | 49 mph |
| 100 km/h | 98.4 km/h | 62 mph | 61 mph |
| 120 km/h | 118.1 km/h | 75 mph | 73 mph |
See individual specs: 245/50R20 · 235/55R19. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.