-3.50%Borderline — noticeable speedometer/odometer error
Speedometer error
With a speedometer calibrated to 285/70R17, fitting 265/65R18 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 38.6 km/h | 25 mph | 24 mph |
| 60 km/h | 57.9 km/h | 37 mph | 36 mph |
| 80 km/h | 77.2 km/h | 50 mph | 48 mph |
| 100 km/h | 96.5 km/h | 62 mph | 60 mph |
| 120 km/h | 115.8 km/h | 75 mph | 72 mph |
Full comparison
285/70R17
Overall diameter830.8 mm · 32.71 in
Section width285 mm · 11.22 in
Sidewall height199.5 mm · 7.85 in
Circumference2610.0 mm · 102.8 in
Revolutions per mile617
Revolutions per km383
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
-3.5%Borderline — noticeable speedometer/odometer error
Original
Overall diameter830.8 mm · 32.71 in
Sidewall height199.5 mm
Circumference2,610 mm
Revolutions / mile616.6
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 -3.5%. 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 | 38.6 km/h | 25 mph | 24 mph |
| 60 km/h | 57.9 km/h | 37 mph | 36 mph |
| 80 km/h | 77.2 km/h | 50 mph | 48 mph |
| 100 km/h | 96.5 km/h | 62 mph | 60 mph |
| 120 km/h | 115.8 km/h | 75 mph | 72 mph |
See individual specs: 285/70R17 · 265/65R18. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.