-0.14%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 265/70R17, fitting 265/65R18 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 39.9 km/h | 25 mph | 25 mph |
| 60 km/h | 59.9 km/h | 37 mph | 37 mph |
| 80 km/h | 79.9 km/h | 50 mph | 50 mph |
| 100 km/h | 99.9 km/h | 62 mph | 62 mph |
| 120 km/h | 119.8 km/h | 75 mph | 74 mph |
Full comparison
265/70R17
Overall diameter802.8 mm · 31.61 in
Section width265 mm · 10.43 in
Sidewall height185.5 mm · 7.30 in
Circumference2522.1 mm · 99.3 in
Revolutions per mile638
Revolutions per km396
265/65R18
Overall diameter801.7 mm · 31.56 in
Section width265 mm · 10.43 in
Sidewall height172.3 mm · 6.78 in
Circumference2518.6 mm · 99.2 in
Revolutions per mile639
Revolutions per km397
-0.14%Safe swap — speedometer error is minor
Original
Overall diameter802.8 mm · 31.61 in
Sidewall height185.5 mm
Circumference2,522.1 mm
Revolutions / mile638.1
New
Overall diameter801.7 mm · 31.56 in
Sidewall height172.3 mm
Circumference2,518.6 mm
Revolutions / mile639
Speedometer & odometer error
The new tire changes overall diameter by -0.14%. 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 | 39.9 km/h | 25 mph | 25 mph |
| 60 km/h | 59.9 km/h | 37 mph | 37 mph |
| 80 km/h | 79.9 km/h | 50 mph | 50 mph |
| 100 km/h | 99.9 km/h | 62 mph | 62 mph |
| 120 km/h | 119.8 km/h | 75 mph | 74 mph |
See individual specs: 265/70R17 · 265/65R18. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.