+1.37%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 255/45R20, fitting 265/50R19 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.5 km/h | 25 mph | 25 mph |
| 60 km/h | 60.8 km/h | 37 mph | 38 mph |
| 80 km/h | 81.1 km/h | 50 mph | 50 mph |
| 100 km/h | 101.4 km/h | 62 mph | 63 mph |
| 120 km/h | 121.6 km/h | 75 mph | 76 mph |
Full comparison
255/45R20
Overall diameter737.5 mm · 29.04 in
Section width255 mm · 10.04 in
Sidewall height114.8 mm · 4.52 in
Circumference2316.9 mm · 91.2 in
Revolutions per mile695
Revolutions per km432
265/50R19
Overall diameter747.6 mm · 29.43 in
Section width265 mm · 10.43 in
Sidewall height132.5 mm · 5.22 in
Circumference2348.7 mm · 92.5 in
Revolutions per mile685
Revolutions per km426
+1.37%Safe swap — speedometer error is minor
Original
Overall diameter737.5 mm · 29.04 in
Sidewall height114.8 mm
Circumference2,316.9 mm
Revolutions / mile694.6
New
Overall diameter747.6 mm · 29.43 in
Sidewall height132.5 mm
Circumference2,348.7 mm
Revolutions / mile685.2
Speedometer & odometer error
The new tire changes overall diameter by +1.37%. 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 | 40.5 km/h | 25 mph | 25 mph |
| 60 km/h | 60.8 km/h | 37 mph | 38 mph |
| 80 km/h | 81.1 km/h | 50 mph | 50 mph |
| 100 km/h | 101.4 km/h | 62 mph | 63 mph |
| 120 km/h | 121.6 km/h | 75 mph | 76 mph |
See individual specs: 255/45R20 · 265/50R19. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.