-1.14%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 235/45R18, fitting 255/35R19 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 39.5 km/h | 25 mph | 25 mph |
| 60 km/h | 59.3 km/h | 37 mph | 37 mph |
| 80 km/h | 79.1 km/h | 50 mph | 49 mph |
| 100 km/h | 98.9 km/h | 62 mph | 61 mph |
| 120 km/h | 118.6 km/h | 75 mph | 74 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
255/35R19
Overall diameter661.1 mm · 26.03 in
Section width255 mm · 10.04 in
Sidewall height89.3 mm · 3.51 in
Circumference2076.9 mm · 81.8 in
Revolutions per mile775
Revolutions per km481
-1.14%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 diameter661.1 mm · 26.03 in
Sidewall height89.3 mm
Circumference2,076.9 mm
Revolutions / mile774.9
Speedometer & odometer error
The new tire changes overall diameter by -1.14%. 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 | 39.5 km/h | 25 mph | 25 mph |
| 60 km/h | 59.3 km/h | 37 mph | 37 mph |
| 80 km/h | 79.1 km/h | 50 mph | 49 mph |
| 100 km/h | 98.9 km/h | 62 mph | 61 mph |
| 120 km/h | 118.6 km/h | 75 mph | 74 mph |
See individual specs: 235/45R18 · 255/35R19. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.