Mont. Code Ann. § 61-9-406

Restrictions as to tire equipment – particular tires, chains, or traction devices – definitions

(1) A solid rubber tire on a vehicle must have rubber on its entire traction surface at least 1 inch thick above the edge of the flange of the entire periphery.

(2) A person may not operate or move on a highway a motor vehicle, trailer, or semitrailer having a metal tire in contact with the roadway.

(3) A tire on a vehicle moved on a highway may not have on its periphery a block, stud, flange, cleat, spike, or other protuberance of a material other than rubber that projects beyond the tread of the traction surface of the tire, except that it is permissible to use farm machinery with tires having protuberances that will not injure the highway. It is also permissible to use tire chains of reasonable proportions or pneumatic tires, the traction surfaces of which have been embedded with material, such as wood, wire, plastic or metal, that may not protrude more than one-sixteenth of an inch beyond the tire tread or that are clearly marked by the manufacturer on the sidewall "all season m&s" (or "all season mud and snow"), upon a vehicle when required for safety because of snow, ice, or other conditions tending to cause a vehicle to skid. Except as provided in subsection (4), the use of pneumatic tires embedded as provided in this section is permitted only between October 1 and May 31 of each year, except that one of those tires may be used for a spare in case of tire failure. School buses equipped with such embedded pneumatic tires may operate from August 15 through the following June 15.

(4) Pneumatic tires that feature an embedded block, stud, flange, cleat, spike, or other protuberance that is retractable may be used at any time of the year. However, the protuberance may not be engaged or extended other than between October 1 and May 31 of each year on roads that do not contain ice or snow.

(5) The department of transportation and local authorities, as defined in 61-8-102, in their respective jurisdictions may in their discretion issue special permits authorizing the operation upon a highway of farm tractors or other farm machinery or of traction engines or tractors having movable tracks with transverse corrugations upon the periphery of the movable tracks, the operation of which upon the highway would otherwise be prohibited under this section.

(6) The department of transportation may determine at any time that dangerous or unsafe conditions on a highway require particular tires, tire chains, or traction devices for vehicles in addition to or beyond the ordinary pneumatic rubber tires.

(7) The department of transportation shall place and maintain signs and other traffic control devices on a highway designated under subsection (6) that indicate the tire, tire chain, or traction device requirement determined for vehicles. The signs or traffic control devices may not prohibit the use of pneumatic tires embedded as provided in subsection (3) between October 1 and May 31 of each year, but when the department of transportation determines that chains are required and that no other traction devices will suffice, the requirement is applicable to tires on driver wheels of one axle, as defined in 61-10-104, of a vehicle, including embedded tires. The signs or traffic control devices may differentiate in requirements for four-wheel-drive vehicles in gear.

(8) A violation of subsection (6) or (7) is subject to the penalties provided in 61-9-520.

(9) As used in this section:

(a) "metal tire" means a tire the surface of which in contact with the highway is wholly or partly metal or other hard, nonresilient material; and

(b) "pneumatic tire" means a tire in which compressed air or nitrogen is designed to support the load.