-5.11%Not recommended — recalibrate the speedometer
Speedometer error
With a speedometer calibrated to 235/75R15, fitting 225/70R15 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 38.0 km/h | 25 mph | 24 mph |
| 60 km/h | 56.9 km/h | 37 mph | 35 mph |
| 80 km/h | 75.9 km/h | 50 mph | 47 mph |
| 100 km/h | 94.9 km/h | 62 mph | 59 mph |
| 120 km/h | 113.9 km/h | 75 mph | 71 mph |
Full comparison
235/75R15
Overall diameter733.5 mm · 28.88 in
Section width235 mm · 9.25 in
Sidewall height176.3 mm · 6.94 in
Circumference2304.4 mm · 90.7 in
Revolutions per mile698
Revolutions per km434
225/70R15
Overall diameter696.0 mm · 27.40 in
Section width225 mm · 8.86 in
Sidewall height157.5 mm · 6.20 in
Circumference2186.5 mm · 86.1 in
Revolutions per mile736
Revolutions per km457
-5.11%Not recommended — recalibrate the speedometer
Original
Overall diameter733.5 mm · 28.88 in
Sidewall height176.3 mm
Circumference2,304.4 mm
Revolutions / mile698.4
New
Overall diameter696 mm · 27.4 in
Sidewall height157.5 mm
Circumference2,186.5 mm
Revolutions / mile736
Speedometer & odometer error
The new tire changes overall diameter by -5.11%. 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 | 38 km/h | 25 mph | 24 mph |
| 60 km/h | 56.9 km/h | 37 mph | 35 mph |
| 80 km/h | 75.9 km/h | 50 mph | 47 mph |
| 100 km/h | 94.9 km/h | 62 mph | 59 mph |
| 120 km/h | 113.9 km/h | 75 mph | 71 mph |
See individual specs: 235/75R15 · 225/70R15. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.