-3.02%Borderline — noticeable speedometer/odometer error
Speedometer error
With a speedometer calibrated to 275/70R18, fitting 275/70R17 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 38.8 km/h | 25 mph | 24 mph |
| 60 km/h | 58.2 km/h | 37 mph | 36 mph |
| 80 km/h | 77.6 km/h | 50 mph | 48 mph |
| 100 km/h | 97.0 km/h | 62 mph | 60 mph |
| 120 km/h | 116.4 km/h | 75 mph | 72 mph |
Full comparison
275/70R18
Overall diameter842.2 mm · 33.16 in
Section width275 mm · 10.83 in
Sidewall height192.5 mm · 7.58 in
Circumference2645.8 mm · 104.2 in
Revolutions per mile608
Revolutions per km378
275/70R17
Overall diameter816.8 mm · 32.16 in
Section width275 mm · 10.83 in
Sidewall height192.5 mm · 7.58 in
Circumference2566.1 mm · 101.0 in
Revolutions per mile627
Revolutions per km390
-3.02%Borderline — noticeable speedometer/odometer error
Original
Overall diameter842.2 mm · 33.16 in
Sidewall height192.5 mm
Circumference2,645.8 mm
Revolutions / mile608.3
New
Overall diameter816.8 mm · 32.16 in
Sidewall height192.5 mm
Circumference2,566.1 mm
Revolutions / mile627.2
Speedometer & odometer error
The new tire changes overall diameter by -3.02%. 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 | 38.8 km/h | 25 mph | 24 mph |
| 60 km/h | 58.2 km/h | 37 mph | 36 mph |
| 80 km/h | 77.6 km/h | 50 mph | 48 mph |
| 100 km/h | 97 km/h | 62 mph | 60 mph |
| 120 km/h | 116.4 km/h | 75 mph | 72 mph |
See individual specs: 275/70R18 · 275/70R17. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.