-4.22%Borderline — noticeable speedometer/odometer error
Speedometer error
With a speedometer calibrated to 285/45R22, fitting 275/45R21 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 38.3 km/h | 25 mph | 24 mph |
| 60 km/h | 57.5 km/h | 37 mph | 36 mph |
| 80 km/h | 76.6 km/h | 50 mph | 48 mph |
| 100 km/h | 95.8 km/h | 62 mph | 60 mph |
| 120 km/h | 114.9 km/h | 75 mph | 71 mph |
Full comparison
285/45R22
Overall diameter815.3 mm · 32.10 in
Section width285 mm · 11.22 in
Sidewall height128.3 mm · 5.05 in
Circumference2561.3 mm · 100.8 in
Revolutions per mile628
Revolutions per km390
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
-4.22%Borderline — noticeable speedometer/odometer error
Original
Overall diameter815.3 mm · 32.1 in
Sidewall height128.3 mm
Circumference2,561.3 mm
Revolutions / mile628.3
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 -4.22%. 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 | 38.3 km/h | 25 mph | 24 mph |
| 60 km/h | 57.5 km/h | 37 mph | 36 mph |
| 80 km/h | 76.6 km/h | 50 mph | 48 mph |
| 100 km/h | 95.8 km/h | 62 mph | 60 mph |
| 120 km/h | 114.9 km/h | 75 mph | 71 mph |
See individual specs: 285/45R22 · 275/45R21. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.