+4.22%Borderline — noticeable speedometer/odometer error
Speedometer error
With a speedometer calibrated to 265/30R19, fitting 235/45R18 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 41.7 km/h | 25 mph | 26 mph |
| 60 km/h | 62.5 km/h | 37 mph | 39 mph |
| 80 km/h | 83.4 km/h | 50 mph | 52 mph |
| 100 km/h | 104.2 km/h | 62 mph | 65 mph |
| 120 km/h | 125.1 km/h | 75 mph | 78 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
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
+4.22%Borderline — noticeable speedometer/odometer error
Original
Overall diameter641.6 mm · 25.26 in
Sidewall height79.5 mm
Circumference2,015.6 mm
Revolutions / mile798.4
New
Overall diameter668.7 mm · 26.33 in
Sidewall height105.8 mm
Circumference2,100.8 mm
Revolutions / mile766.1
Speedometer & odometer error
The new tire changes overall diameter by +4.22%. 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 | 41.7 km/h | 25 mph | 26 mph |
| 60 km/h | 62.5 km/h | 37 mph | 39 mph |
| 80 km/h | 83.4 km/h | 50 mph | 52 mph |
| 100 km/h | 104.2 km/h | 62 mph | 65 mph |
| 120 km/h | 125.1 km/h | 75 mph | 78 mph |
See individual specs: 265/30R19 · 235/45R18. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.