-3.85%Borderline — noticeable speedometer/odometer error
Speedometer error
With a speedometer calibrated to 305/40R22, fitting 265/45R21 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 38.5 km/h | 25 mph | 24 mph |
| 60 km/h | 57.7 km/h | 37 mph | 36 mph |
| 80 km/h | 76.9 km/h | 50 mph | 48 mph |
| 100 km/h | 96.2 km/h | 62 mph | 60 mph |
| 120 km/h | 115.4 km/h | 75 mph | 72 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
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
-3.85%Borderline — noticeable speedometer/odometer error
Original
Overall diameter802.8 mm · 31.61 in
Sidewall height122 mm
Circumference2,522.1 mm
Revolutions / mile638.1
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 -3.85%. 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 | 38.5 km/h | 25 mph | 24 mph |
| 60 km/h | 57.7 km/h | 37 mph | 36 mph |
| 80 km/h | 76.9 km/h | 50 mph | 48 mph |
| 100 km/h | 96.2 km/h | 62 mph | 60 mph |
| 120 km/h | 115.4 km/h | 75 mph | 72 mph |
See individual specs: 305/40R22 · 265/45R21. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.