P Metric
With the P-Metric system, Section Width is measured in millimeters.
To convert millimeters into inches, divide by 25.4. The Aspect Ratio (Section Height divided by Section Width) helps provide more dimensional information about the tire size.
Example:

(1) P = Certain tire type used on light duty vehicles such as passenger
cars
(2) Section Width in millimeters
(3) Aspect Ratio (= section height 7 section width).
(4) R = Radial Construction
(5) Rim diameter in inches
See also:
Cruise control
Cruise control enables you to maintain a constant vehicle speed without holding
your foot on the accelerator pedal and it is operative when the vehicle speed is
25 mph (40 km/h) or more.
WARNING
...
Safety
As of this writing, the all-new Impreza hasn't been crash-tested. The WRX
retains its Top Safety Pick designation from the Insurance Institute for Highway
safety, having earned top scores of Good ...
Flat tires
If you have a flat tire while driving, never brake suddenly; keep driving straight
ahead while gradually reducing speed. Then slowly pull off the road to a safe place. ...
