-7.09%Not recommended — recalibrate the speedometer
Speedometer error
With a speedometer calibrated to 285/75R16, fitting 245/70R17 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 37.2 km/h | 25 mph | 23 mph |
| 60 km/h | 55.7 km/h | 37 mph | 35 mph |
| 80 km/h | 74.3 km/h | 50 mph | 46 mph |
| 100 km/h | 92.9 km/h | 62 mph | 58 mph |
| 120 km/h | 111.5 km/h | 75 mph | 69 mph |
Full comparison
285/75R16
Overall diameter833.9 mm · 32.83 in
Section width285 mm · 11.22 in
Sidewall height213.8 mm · 8.42 in
Circumference2619.8 mm · 103.1 in
Revolutions per mile614
Revolutions per km382
245/70R17
Overall diameter774.8 mm · 30.50 in
Section width245 mm · 9.65 in
Sidewall height171.5 mm · 6.75 in
Circumference2434.1 mm · 95.8 in
Revolutions per mile661
Revolutions per km411
-7.09%Not recommended — recalibrate the speedometer
Original
Overall diameter833.9 mm · 32.83 in
Sidewall height213.8 mm
Circumference2,619.8 mm
Revolutions / mile614.3
New
Overall diameter774.8 mm · 30.5 in
Sidewall height171.5 mm
Circumference2,434.1 mm
Revolutions / mile661.2
Speedometer & odometer error
The new tire changes overall diameter by -7.09%. 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 | 37.2 km/h | 25 mph | 23 mph |
| 60 km/h | 55.7 km/h | 37 mph | 35 mph |
| 80 km/h | 74.3 km/h | 50 mph | 46 mph |
| 100 km/h | 92.9 km/h | 62 mph | 58 mph |
| 120 km/h | 111.5 km/h | 75 mph | 69 mph |
See individual specs: 285/75R16 · 245/70R17. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.