-1.04%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 265/40R22, fitting 255/40R22 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 39.6 km/h | 25 mph | 25 mph |
| 60 km/h | 59.4 km/h | 37 mph | 37 mph |
| 80 km/h | 79.2 km/h | 50 mph | 49 mph |
| 100 km/h | 99.0 km/h | 62 mph | 61 mph |
| 120 km/h | 118.8 km/h | 75 mph | 74 mph |
Full comparison
265/40R22
Overall diameter770.8 mm · 30.35 in
Section width265 mm · 10.43 in
Sidewall height106.0 mm · 4.17 in
Circumference2421.5 mm · 95.3 in
Revolutions per mile665
Revolutions per km413
255/40R22
Overall diameter762.8 mm · 30.03 in
Section width255 mm · 10.04 in
Sidewall height102.0 mm · 4.02 in
Circumference2396.4 mm · 94.3 in
Revolutions per mile672
Revolutions per km417
-1.04%Safe swap — speedometer error is minor
Original
Overall diameter770.8 mm · 30.35 in
Sidewall height106 mm
Circumference2,421.5 mm
Revolutions / mile664.6
New
Overall diameter762.8 mm · 30.03 in
Sidewall height102 mm
Circumference2,396.4 mm
Revolutions / mile671.6
Speedometer & odometer error
The new tire changes overall diameter by -1.04%. 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 | 39.6 km/h | 25 mph | 25 mph |
| 60 km/h | 59.4 km/h | 37 mph | 37 mph |
| 80 km/h | 79.2 km/h | 50 mph | 49 mph |
| 100 km/h | 99 km/h | 62 mph | 61 mph |
| 120 km/h | 118.8 km/h | 75 mph | 74 mph |
See individual specs: 265/40R22 · 255/40R22. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.