+1.79%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 285/35R22, fitting 265/45R21 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.7 km/h | 25 mph | 25 mph |
| 60 km/h | 61.1 km/h | 37 mph | 38 mph |
| 80 km/h | 81.4 km/h | 50 mph | 51 mph |
| 100 km/h | 101.8 km/h | 62 mph | 63 mph |
| 120 km/h | 122.2 km/h | 75 mph | 76 mph |
Full comparison
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
265/45R21
Overall diameter771.9 mm · 30.39 in
Section width265 mm · 10.43 in
Sidewall height119.3 mm · 4.69 in
Circumference2425.0 mm · 95.5 in
Revolutions per mile664
Revolutions per km412
+1.79%Safe swap — speedometer error is minor
Original
Overall diameter758.3 mm · 29.85 in
Sidewall height99.8 mm
Circumference2,382.3 mm
Revolutions / mile675.6
New
Overall diameter771.9 mm · 30.39 in
Sidewall height119.3 mm
Circumference2,425 mm
Revolutions / mile663.6
Speedometer & odometer error
The new tire changes overall diameter by +1.79%. 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 | 40.7 km/h | 25 mph | 25 mph |
| 60 km/h | 61.1 km/h | 37 mph | 38 mph |
| 80 km/h | 81.4 km/h | 50 mph | 51 mph |
| 100 km/h | 101.8 km/h | 62 mph | 63 mph |
| 120 km/h | 122.2 km/h | 75 mph | 76 mph |
See individual specs: 285/35R22 · 265/45R21. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.