+0.46%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 255/55R18, fitting 235/55R19 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.2 km/h | 25 mph | 25 mph |
| 60 km/h | 60.3 km/h | 37 mph | 37 mph |
| 80 km/h | 80.4 km/h | 50 mph | 50 mph |
| 100 km/h | 100.5 km/h | 62 mph | 62 mph |
| 120 km/h | 120.6 km/h | 75 mph | 75 mph |
Full comparison
255/55R18
Overall diameter737.7 mm · 29.04 in
Section width255 mm · 10.04 in
Sidewall height140.3 mm · 5.52 in
Circumference2317.6 mm · 91.2 in
Revolutions per mile694
Revolutions per km431
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
+0.46%Safe swap — speedometer error is minor
Original
Overall diameter737.7 mm · 29.04 in
Sidewall height140.3 mm
Circumference2,317.6 mm
Revolutions / mile694.4
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 +0.46%. 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 | 40.2 km/h | 25 mph | 25 mph |
| 60 km/h | 60.3 km/h | 37 mph | 37 mph |
| 80 km/h | 80.4 km/h | 50 mph | 50 mph |
| 100 km/h | 100.5 km/h | 62 mph | 62 mph |
| 120 km/h | 120.6 km/h | 75 mph | 75 mph |
See individual specs: 255/55R18 · 235/55R19. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.