+2.82%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 265/30R19, fitting 225/45R18 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 41.1 km/h | 25 mph | 26 mph |
| 60 km/h | 61.7 km/h | 37 mph | 38 mph |
| 80 km/h | 82.3 km/h | 50 mph | 51 mph |
| 100 km/h | 102.8 km/h | 62 mph | 64 mph |
| 120 km/h | 123.4 km/h | 75 mph | 77 mph |
Full comparison
265/30R19
Overall diameter641.6 mm · 25.26 in
Section width265 mm · 10.43 in
Sidewall height79.5 mm · 3.13 in
Circumference2015.6 mm · 79.4 in
Revolutions per mile798
Revolutions per km496
225/45R18
Overall diameter659.7 mm · 25.97 in
Section width225 mm · 8.86 in
Sidewall height101.3 mm · 3.99 in
Circumference2072.5 mm · 81.6 in
Revolutions per mile777
Revolutions per km483
+2.82%Safe swap — speedometer error is minor
Original
Overall diameter641.6 mm · 25.26 in
Sidewall height79.5 mm
Circumference2,015.6 mm
Revolutions / mile798.4
New
Overall diameter659.7 mm · 25.97 in
Sidewall height101.3 mm
Circumference2,072.5 mm
Revolutions / mile776.5
Speedometer & odometer error
The new tire changes overall diameter by +2.82%. 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 | 41.1 km/h | 25 mph | 26 mph |
| 60 km/h | 61.7 km/h | 37 mph | 38 mph |
| 80 km/h | 82.3 km/h | 50 mph | 51 mph |
| 100 km/h | 102.8 km/h | 62 mph | 64 mph |
| 120 km/h | 123.4 km/h | 75 mph | 77 mph |
See individual specs: 265/30R19 · 225/45R18. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.