Maine Tire Regulations

Studded tires are permitted from October 2 to April 30. Permissible when icy road conditions exist. Permits can be issued to use studded tires during prohibited months. Special mileage commercial tire” means a tire manufactured with an extra layer of rubber between the cord body and original tread design, which extra layer is designed for the purpose of recutting or regrooving, and which tire is specifically labelled as a “special mileage commercial tire. A motor vehicle may not be operated on a public way unless it is equipped with tires in safe operating condition. A tire mounted on a motor vehicle is not considered to be in safe operating condition unless it meets the visual and tread depth requirements set forth in subsections 3 and 4 and the vehicle is in compliance with the frame height requirements provided in section 1920.

A tire is not in safe operating condition if that tire has: A. A fabric break or a cut in excess of one inch in any direction as measured on the outside of the tire and deep enough to reach the body cords;

A temporary repair by the use of blowout patches or boots;

A bump, bulge or knot related to separation or partial failure of the tire structure;

A portion of the ply or cord structure exposed; or

Sidewalls damaged to the extent that the body cords are damaged.

A tire is not in safe operating condition if it is worn to the point where less than 2/32 inch of tread design remains at all points at which gauge readings are required. Tread depth must be measured as follows. Tire tread depth must be measured by a tread depth gauge that is calibrated in 1/32 inch. Readings must be taken in all major tread grooves and must include at least 2 points not closer than 15 inches. Readings for a tire that has the tread design running across the tire or for a siped tire must be taken at or near the center of the tire at 2 points of the circumference not closer than 15 inches.

Source: http://legislature.maine.gov/statutes/29-A/title29-Asec1917.html
Source: https://legislature.maine.gov/statutes/29-A/title29-Ach17.pdf