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:
The Inside
The interior is quiet enough at idle that one time I didn't even realize it
was running. That's when I recognized Subaru finally seems to have licked this
engine's chronic idle vibration. In this ...
To arm the system using remote transmitter
1. Close all windows.
2. Remove the key from the ignition switch.
3. Open the doors and get out of the vehicle.
4. Make sure that the engine hood (and the trunk lid on the 4-door) are locked.
5. C ...
ABS system self-check
Just after the vehicle is started, you may
feel on the brake pedal a vibration similar
to when the ABS operates, and you may
also hear the sound of the ABS working
from the engine compartment. ...
