-0.90%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 175/65R15, fitting 185/60R15 makes it read as follows:
| Speedo shows | True speed | Speedo shows | True speed |
|---|---|---|---|
| 40 km/h | 39.6 km/h | 25 mph | 25 mph |
| 60 km/h | 59.5 km/h | 37 mph | 37 mph |
| 80 km/h | 79.3 km/h | 50 mph | 49 mph |
| 100 km/h | 99.1 km/h | 62 mph | 62 mph |
| 120 km/h | 118.9 km/h | 75 mph | 74 mph |
Full comparison
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
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
-0.9%Safe swap — speedometer error is minor
Original
Overall diameter608.5 mm · 23.96 in
Sidewall height113.8 mm
Circumference1,911.7 mm
Revolutions / mile841.9
New
Overall diameter603 mm · 23.74 in
Sidewall height111 mm
Circumference1,894.4 mm
Revolutions / mile849.5
Speedometer & odometer error
The new tire changes overall diameter by -0.9%. 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 | 39.6 km/h | 25 mph | 25 mph |
| 60 km/h | 59.5 km/h | 37 mph | 37 mph |
| 80 km/h | 79.3 km/h | 50 mph | 49 mph |
| 100 km/h | 99.1 km/h | 62 mph | 62 mph |
| 120 km/h | 118.9 km/h | 75 mph | 74 mph |
See individual specs: 175/65R15 · 185/60R15. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.