+1.88%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 265/65R18, fitting 275/70R17 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.8 km/h | 25 mph | 25 mph |
| 60 km/h | 61.1 km/h | 37 mph | 38 mph |
| 80 km/h | 81.5 km/h | 50 mph | 51 mph |
| 100 km/h | 101.9 km/h | 62 mph | 63 mph |
| 120 km/h | 122.3 km/h | 75 mph | 76 mph |
Full comparison
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
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
+1.88%Safe swap — speedometer error is minor
Original
Overall diameter801.7 mm · 31.56 in
Sidewall height172.3 mm
Circumference2,518.6 mm
Revolutions / mile639
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 +1.88%. 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 | 40.8 km/h | 25 mph | 25 mph |
| 60 km/h | 61.1 km/h | 37 mph | 38 mph |
| 80 km/h | 81.5 km/h | 50 mph | 51 mph |
| 100 km/h | 101.9 km/h | 62 mph | 63 mph |
| 120 km/h | 122.3 km/h | 75 mph | 76 mph |
See individual specs: 265/65R18 · 275/70R17. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.