Understanding tire codes and correct pressure

Sidewall numbers are not decoration. Misreading them hurts handling and fuel use.

Example code 205/55 R16 91V: 205 mm width, 55% aspect ratio, radial construction, 16-inch rim, load index 91, speed rating V.

Daily pressure is not the max number on the sidewall. That max is a capability limit; the door sticker or manual lists operating pressure.

Check when tires are cold. After a long drive, air expands and the gauge can look “fine” even if cold pressure was low.

Front and rear pressures can differ—do not copy one number everywhere.

Rotate tires as the maker recommends, and replace before tread wear indicators are flush. Bald tires stretch wet braking distances sharply.

Keep the spare inflated and ready. Many roadside failures start with a flat spare nobody checked.