-2.98%Safe swap — speedometer error is minor
Speedometer error
With a speedometer calibrated to 185/65R15, fitting 185/60R15 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
185/65R15
Overall diameter621.5 mm · 24.47 in
Section width185 mm · 7.28 in
Sidewall height120.3 mm · 4.73 in
Circumference1952.5 mm · 76.9 in
Revolutions per mile824
Revolutions per km512
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
-2.98%Safe swap — speedometer error is minor
Original
Overall diameter621.5 mm · 24.47 in
Sidewall height120.3 mm
Circumference1,952.5 mm
Revolutions / mile824.2
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 -2.98%. 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: 185/65R15 · 185/60R15. A change this size can affect ABS/speed calibration — see wheel-speed codes if a light appears.