| Parameter | 195/65 R15 | 205/60 R15 | Difference |
|---|---|---|---|
| Sidewall height, mm | — | — | — |
| Overall diameter, mm | — | — | — |
| Circumference, mm | — | — | — |
| Revolutions per km | — | — | — |
| Ground clearance | — | — | — |
speedometer reads 100 km/h - actual speed: —
How to read a size
In the 195/65 R15 marking: 195 is the tread width in mm, 65 is the sidewall height as a percentage of the width, R15 is the rim diameter in inches. Overall diameter = rim + two sidewall heights.
Acceptable deviation
A change of overall diameter within ±3% is usually considered safe: beyond that the tire may rub the arches, the speedometer and odometer drift noticeably and drivetrain load changes. The exact approved sizes for your car are in the manual or on the placard in the driver's door jamb.
Speedometer
The speedometer counts wheel revolutions, so with a larger diameter your actual speed is higher than indicated, with a smaller one it is lower. Factory calibration usually overstates speed by a few percent, so a slight increase in diameter often brings the speedometer closer to the truth rather than further from it.