+1.56%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 255/65R17, fitting 265/60R18 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.6 km/h | 25 mph | 25 mph |
| 60 km/h | 60.9 km/h | 37 mph | 38 mph |
| 80 km/h | 81.2 km/h | 50 mph | 50 mph |
| 100 km/h | 101.6 km/h | 62 mph | 63 mph |
| 120 km/h | 121.9 km/h | 75 mph | 76 mph |
Full comparison
255/65R17
Overall diameter763.3 mm · 30.05 in
Section width255 mm · 10.04 in
Sidewall height165.8 mm · 6.53 in
Circumference2398.0 mm · 94.4 in
Revolutions per mile671
Revolutions per km417
265/60R18
Overall diameter775.2 mm · 30.52 in
Section width265 mm · 10.43 in
Sidewall height159.0 mm · 6.26 in
Circumference2435.4 mm · 95.9 in
Revolutions per mile661
Revolutions per km411
+1.56%Safe swap — speedometer error is minor
Original
Overall diameter763.3 mm · 30.05 in
Sidewall height165.8 mm
Circumference2,398 mm
Revolutions / mile671.1
New
Overall diameter775.2 mm · 30.52 in
Sidewall height159 mm
Circumference2,435.4 mm
Revolutions / mile660.8
Speedometer & odometer error
The new tire changes overall diameter by +1.56%. 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 | 40.6 km/h | 25 mph | 25 mph |
| 60 km/h | 60.9 km/h | 37 mph | 38 mph |
| 80 km/h | 81.2 km/h | 50 mph | 50 mph |
| 100 km/h | 101.6 km/h | 62 mph | 63 mph |
| 120 km/h | 121.9 km/h | 75 mph | 76 mph |
See individual specs: 255/65R17 · 265/60R18. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.