+0.01%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 255/55R19, fitting 255/60R18 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.0 km/h | 25 mph | 25 mph |
| 60 km/h | 60.0 km/h | 37 mph | 37 mph |
| 80 km/h | 80.0 km/h | 50 mph | 50 mph |
| 100 km/h | 100.0 km/h | 62 mph | 62 mph |
| 120 km/h | 120.0 km/h | 75 mph | 75 mph |
Full comparison
255/55R19
Overall diameter763.1 mm · 30.04 in
Section width255 mm · 10.04 in
Sidewall height140.3 mm · 5.52 in
Circumference2397.3 mm · 94.4 in
Revolutions per mile671
Revolutions per km417
255/60R18
Overall diameter763.2 mm · 30.05 in
Section width255 mm · 10.04 in
Sidewall height153.0 mm · 6.02 in
Circumference2397.7 mm · 94.4 in
Revolutions per mile671
Revolutions per km417
+0.01%Safe swap — speedometer error is minor
Original
Overall diameter763.1 mm · 30.04 in
Sidewall height140.3 mm
Circumference2,397.3 mm
Revolutions / mile671.3
New
Overall diameter763.2 mm · 30.05 in
Sidewall height153 mm
Circumference2,397.7 mm
Revolutions / mile671.2
Speedometer & odometer error
The new tire changes overall diameter by +0.01%. 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 km/h | 25 mph | 25 mph |
| 60 km/h | 60 km/h | 37 mph | 37 mph |
| 80 km/h | 80 km/h | 50 mph | 50 mph |
| 100 km/h | 100 km/h | 62 mph | 62 mph |
| 120 km/h | 120 km/h | 75 mph | 75 mph |
See individual specs: 255/55R19 · 255/60R18. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.