+1.48%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 235/45R18, fitting 245/40R19 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.6 km/h | 25 mph | 25 mph |
| 60 km/h | 60.9 km/h | 37 mph | 38 mph |
| 80 km/h | 81.2 km/h | 50 mph | 50 mph |
| 100 km/h | 101.5 km/h | 62 mph | 63 mph |
| 120 km/h | 121.8 km/h | 75 mph | 76 mph |
Full comparison
235/45R18
Overall diameter668.7 mm · 26.33 in
Section width235 mm · 9.25 in
Sidewall height105.8 mm · 4.16 in
Circumference2100.8 mm · 82.7 in
Revolutions per mile766
Revolutions per km476
245/40R19
Overall diameter678.6 mm · 26.72 in
Section width245 mm · 9.65 in
Sidewall height98.0 mm · 3.86 in
Circumference2131.9 mm · 83.9 in
Revolutions per mile755
Revolutions per km469
+1.48%Safe swap — speedometer error is minor
Original
Overall diameter668.7 mm · 26.33 in
Sidewall height105.8 mm
Circumference2,100.8 mm
Revolutions / mile766.1
New
Overall diameter678.6 mm · 26.72 in
Sidewall height98 mm
Circumference2,131.9 mm
Revolutions / mile754.9
Speedometer & odometer error
The new tire changes overall diameter by +1.48%. 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 | 40.6 km/h | 25 mph | 25 mph |
| 60 km/h | 60.9 km/h | 37 mph | 38 mph |
| 80 km/h | 81.2 km/h | 50 mph | 50 mph |
| 100 km/h | 101.5 km/h | 62 mph | 63 mph |
| 120 km/h | 121.8 km/h | 75 mph | 76 mph |
See individual specs: 235/45R18 · 245/40R19. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.