-1.73%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 245/65R17, fitting 235/65R17 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 39.3 km/h | 25 mph | 24 mph |
| 60 km/h | 59.0 km/h | 37 mph | 37 mph |
| 80 km/h | 78.6 km/h | 50 mph | 49 mph |
| 100 km/h | 98.3 km/h | 62 mph | 61 mph |
| 120 km/h | 117.9 km/h | 75 mph | 73 mph |
Full comparison
245/65R17
Overall diameter750.3 mm · 29.54 in
Section width245 mm · 9.65 in
Sidewall height159.3 mm · 6.27 in
Circumference2357.1 mm · 92.8 in
Revolutions per mile683
Revolutions per km424
235/65R17
Overall diameter737.3 mm · 29.03 in
Section width235 mm · 9.25 in
Sidewall height152.8 mm · 6.01 in
Circumference2316.3 mm · 91.2 in
Revolutions per mile695
Revolutions per km432
-1.73%Safe swap — speedometer error is minor
Original
Overall diameter750.3 mm · 29.54 in
Sidewall height159.3 mm
Circumference2,357.1 mm
Revolutions / mile682.8
New
Overall diameter737.3 mm · 29.03 in
Sidewall height152.8 mm
Circumference2,316.3 mm
Revolutions / mile694.8
Speedometer & odometer error
The new tire changes overall diameter by -1.73%. 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 | 39.3 km/h | 25 mph | 24 mph |
| 60 km/h | 59 km/h | 37 mph | 37 mph |
| 80 km/h | 78.6 km/h | 50 mph | 49 mph |
| 100 km/h | 98.3 km/h | 62 mph | 61 mph |
| 120 km/h | 117.9 km/h | 75 mph | 73 mph |
See individual specs: 245/65R17 · 235/65R17. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.