+0.91%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 185/60R15, fitting 175/65R15 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 40.4 km/h | 25 mph | 25 mph |
| 60 km/h | 60.5 km/h | 37 mph | 38 mph |
| 80 km/h | 80.7 km/h | 50 mph | 50 mph |
| 100 km/h | 100.9 km/h | 62 mph | 63 mph |
| 120 km/h | 121.1 km/h | 75 mph | 75 mph |
Full comparison
185/60R15
Overall diameter603.0 mm · 23.74 in
Section width185 mm · 7.28 in
Sidewall height111.0 mm · 4.37 in
Circumference1894.4 mm · 74.6 in
Revolutions per mile850
Revolutions per km528
175/65R15
Overall diameter608.5 mm · 23.96 in
Section width175 mm · 6.89 in
Sidewall height113.8 mm · 4.48 in
Circumference1911.7 mm · 75.3 in
Revolutions per mile842
Revolutions per km523
+0.91%Safe swap — speedometer error is minor
Original
Overall diameter603 mm · 23.74 in
Sidewall height111 mm
Circumference1,894.4 mm
Revolutions / mile849.5
New
Overall diameter608.5 mm · 23.96 in
Sidewall height113.8 mm
Circumference1,911.7 mm
Revolutions / mile841.9
Speedometer & odometer error
The new tire changes overall diameter by +0.91%. 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 | 40.4 km/h | 25 mph | 25 mph |
| 60 km/h | 60.5 km/h | 37 mph | 38 mph |
| 80 km/h | 80.7 km/h | 50 mph | 50 mph |
| 100 km/h | 100.9 km/h | 62 mph | 63 mph |
| 120 km/h | 121.1 km/h | 75 mph | 75 mph |
See individual specs: 185/60R15 · 175/65R15. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.