Tire Size, Thread Depth, Width and Snow Chains Regulations (USA and Canada)
All tires must be in good condition and have at least 2/32 inch of tread depth remaining.
20-122. Restrictions as to tire equipment.
(a) No vehicle will be allowed to move on any public highway unless equipped with tires of rubber or other resilient material which depend upon compressed air, for support of a load, except by special permission of the Department of Transportation which may grant such special permits upon a showing of necessity. This subsection shall have no application to the movement of farm vehicles on highways.
(b) No tire on a vehicle moved on a highway shall have on its periphery any block, stud, flange, cleat or spike or any other protuberance of any material other than rubber which projects beyond the tread of the traction surface of the tire, except that it shall be permissible to use farm machinery with tires having protuberances which will not injure the highway and except, also, that it shall be permissible to use tire chains of reasonable proportions upon any vehicle when required for safety because of snow, ice or other conditions tending to cause a vehicle to slide or skid. It shall be permissible to use upon any vehicle for increased safety, regular and snow tires with studs which project beyond the tread of the traction surface of the tire not more than one sixteenth of an inch ( 1/16 ) when compressed.
(c) The Department of Transportation or local authorities in their respective jurisdictions may, in their discretion, issue special permits authorizing the operation upon a highway of traction engines or tractors having movable tracks with transverse corrugation upon the periphery of such movable tracks or farm tractors or other farm machinery.
(d) It shall not be unlawful to drive farm tractors on dirt roads from farm to farm: Provided, in doing so they do not damage said dirt roads or interfere with traffic.
(a) A vehicle shall be disapproved if:
Any tire has cuts or snags that expose the cords.
Any tire has a visible bump, bulge, or knot apparently related to tread or sidewall separation or partial failure of the tire structure including bead area.
(b) Tire depth shall be measured by a tread depth gauge which shall be of a type calibrated in thirty-seconds of an inch. Readings shall be taken in two adjacent tread grooves of the tire around the circumference of the tire. Readings for a tire with a tread design that does not have two adjacent grooves near the center shall be taken at the center of the tire around the circumference of the tire. Each tire must be completely lifted from the ground for an inspection to be performed.
Too much or too little air pressure. Bad wear. You need at least 4/32-inch tread depth in every major groove on front tires. You need 2/32 inch on other tires. No fabric should show through the tread or sidewall. Cuts or other damage. Tread separation. Dual tires that come in contact with each other or parts of the vehicle. Mismatched sizes. Radial and bias-ply tires used together. Cut or cracked valve stems. Re-grooved, recapped, or retreaded tires on the front wheels of a bus are prohibited.
Wheel and Rim Problems
Damaged rims. Rust around wheel nuts may mean the nuts are loose–check tightness. After a tire has been changed, stop a short while later and re-check tightness of nuts. Missing clamps, spacers, studs, or lugs means danger. Mismatched, bent, or cracked lock rings are dangerous. Wheels or rims that have had welding repairs are not safe.
Below is a list of states and their tire regulations.
Click on the states below for links to the state's guidelines for for tire regulations for commercial vehicles / heavy haul shipping. These regulations are subject to change for each state. If something doesn't look correct, give us a shout and let us know so we can property update the page.