-5.32%Not recommended — recalibrate the speedometer
Speedometer error
With a speedometer calibrated to 285/45R22, fitting 265/45R21 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 37.9 km/h | 25 mph | 24 mph |
| 60 km/h | 56.8 km/h | 37 mph | 35 mph |
| 80 km/h | 75.7 km/h | 50 mph | 47 mph |
| 100 km/h | 94.7 km/h | 62 mph | 59 mph |
| 120 km/h | 113.6 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
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
-5.32%Not recommended — recalibrate the speedometer
Original
Overall diameter815.3 mm · 32.1 in
Sidewall height128.3 mm
Circumference2,561.3 mm
Revolutions / mile628.3
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 -5.32%. 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 | 37.9 km/h | 25 mph | 24 mph |
| 60 km/h | 56.8 km/h | 37 mph | 35 mph |
| 80 km/h | 75.7 km/h | 50 mph | 47 mph |
| 100 km/h | 94.7 km/h | 62 mph | 59 mph |
| 120 km/h | 113.6 km/h | 75 mph | 71 mph |
See individual specs: 285/45R22 · 265/45R21. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.