+2.98%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 285/35R22, fitting 275/45R21 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 41.2 km/h | 25 mph | 26 mph |
| 60 km/h | 61.8 km/h | 37 mph | 38 mph |
| 80 km/h | 82.4 km/h | 50 mph | 51 mph |
| 100 km/h | 103.0 km/h | 62 mph | 64 mph |
| 120 km/h | 123.6 km/h | 75 mph | 77 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
275/45R21
Overall diameter780.9 mm · 30.74 in
Section width275 mm · 10.83 in
Sidewall height123.8 mm · 4.87 in
Circumference2453.3 mm · 96.6 in
Revolutions per mile656
Revolutions per km408
+2.98%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 diameter780.9 mm · 30.74 in
Sidewall height123.8 mm
Circumference2,453.3 mm
Revolutions / mile656
Speedometer & odometer error
The new tire changes overall diameter by +2.98%. 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 | 41.2 km/h | 25 mph | 26 mph |
| 60 km/h | 61.8 km/h | 37 mph | 38 mph |
| 80 km/h | 82.4 km/h | 50 mph | 51 mph |
| 100 km/h | 103 km/h | 62 mph | 64 mph |
| 120 km/h | 123.6 km/h | 75 mph | 77 mph |
See individual specs: 285/35R22 · 275/45R21. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.