-5.54%Not recommended — recalibrate the speedometer
Speedometer error
With a speedometer calibrated to 305/40R22, fitting 285/35R22 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 37.8 km/h | 25 mph | 23 mph |
| 60 km/h | 56.7 km/h | 37 mph | 35 mph |
| 80 km/h | 75.6 km/h | 50 mph | 47 mph |
| 100 km/h | 94.5 km/h | 62 mph | 59 mph |
| 120 km/h | 113.3 km/h | 75 mph | 70 mph |
Full comparison
305/40R22
Overall diameter802.8 mm · 31.61 in
Section width305 mm · 12.01 in
Sidewall height122.0 mm · 4.80 in
Circumference2522.1 mm · 99.3 in
Revolutions per mile638
Revolutions per km396
285/35R22
Overall diameter758.3 mm · 29.85 in
Section width285 mm · 11.22 in
Sidewall height99.8 mm · 3.93 in
Circumference2382.3 mm · 93.8 in
Revolutions per mile676
Revolutions per km420
-5.54%Not recommended — recalibrate the speedometer
Original
Overall diameter802.8 mm · 31.61 in
Sidewall height122 mm
Circumference2,522.1 mm
Revolutions / mile638.1
New
Overall diameter758.3 mm · 29.85 in
Sidewall height99.8 mm
Circumference2,382.3 mm
Revolutions / mile675.6
Speedometer & odometer error
The new tire changes overall diameter by -5.54%. 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 | 37.8 km/h | 25 mph | 23 mph |
| 60 km/h | 56.7 km/h | 37 mph | 35 mph |
| 80 km/h | 75.6 km/h | 50 mph | 47 mph |
| 100 km/h | 94.5 km/h | 62 mph | 59 mph |
| 120 km/h | 113.3 km/h | 75 mph | 70 mph |
See individual specs: 305/40R22 · 285/35R22. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.