(a) Tread depth. The tread on each tire shall be not less than two thirty-seconds of an inch deep.

(1) Inspection procedure. Passenger car tires have tread depth indicators that become exposed when tread depth is less than two thirty-seconds of an inch. Inspect for indicators in any two adjacent major grooves at three locations spaced approximately equally around the outside of the tire. For vehicles other than passenger cars, it may be necessary to measure tread depth with a tread gauge.

(b) Type. Vehicle shall be equipped with tires on the same axle that are matched in tire size designation, construction, and profile.

(1) Inspection procedures. Examine visually. A major mismatch in tire size designation, construction, and profile between tires on the same axle, or a major deviation from the size as recommended by the manufacturer (e.g., as indicated on the glove box placard on 1968 and later passenger cars) are causes for rejection.

(c) General condition. Tires shall be free from chunking, bumps, knots, or bulges evidencing cord, ply, or tread separation from the casing or other adjacent materials.

(1) Inspection procedure. Examine visually for conditions indicated.

(d) Damage. Tire cords or belting materials shall not be exposed, either to the naked eye or when cuts or abrasions on the tire are probed.

(1) Inspection procedures. Examine visually for conditions indicated, using a blunt instrument if necessary to probe cuts or abrasions.

[38 FR 23950, Sept. 5, 1973, as amended at 39 FR 12868, Apr. 9, 1974; 39 FR 19781, June 4, 1974]