-4.65%Borderline — noticeable speedometer/odometer error
Speedometer error
With a speedometer calibrated to 255/70R18, fitting 265/65R17 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 38.1 km/h | 25 mph | 24 mph |
| 60 km/h | 57.2 km/h | 37 mph | 36 mph |
| 80 km/h | 76.3 km/h | 50 mph | 47 mph |
| 100 km/h | 95.3 km/h | 62 mph | 59 mph |
| 120 km/h | 114.4 km/h | 75 mph | 71 mph |
Full comparison
255/70R18
Overall diameter814.2 mm · 32.06 in
Section width255 mm · 10.04 in
Sidewall height178.5 mm · 7.03 in
Circumference2557.9 mm · 100.7 in
Revolutions per mile629
Revolutions per km391
265/65R17
Overall diameter776.3 mm · 30.56 in
Section width265 mm · 10.43 in
Sidewall height172.3 mm · 6.78 in
Circumference2438.8 mm · 96.0 in
Revolutions per mile660
Revolutions per km410
-4.65%Borderline — noticeable speedometer/odometer error
Original
Overall diameter814.2 mm · 32.06 in
Sidewall height178.5 mm
Circumference2,557.9 mm
Revolutions / mile629.2
New
Overall diameter776.3 mm · 30.56 in
Sidewall height172.3 mm
Circumference2,438.8 mm
Revolutions / mile659.9
Speedometer & odometer error
The new tire changes overall diameter by -4.65%. 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 | 38.1 km/h | 25 mph | 24 mph |
| 60 km/h | 57.2 km/h | 37 mph | 36 mph |
| 80 km/h | 76.3 km/h | 50 mph | 47 mph |
| 100 km/h | 95.3 km/h | 62 mph | 59 mph |
| 120 km/h | 114.4 km/h | 75 mph | 71 mph |
See individual specs: 255/70R18 · 265/65R17. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.