Idaho Tire Regulations
Tire Size, Thread Depth, Width and Snow Chains Regulations (USA and Canada)
Studded snow tires are permissible from October 1 to April 30. There are no specific restrictions on the use of tire chains in Idaho. While it may be legal to use the tires, officials advise against it unless conditions warrant. Studded tires are snow tires with small metal cleats embedded in the tread, and may cause undue wear on bare roadways. There are times when chains are required. Signs will be posted “Chains required beyond this point” when the road is snow-covered or icy. 2/32 inch is the minimum legal tread depth.
Idaho law says use of studded tires is only legal between October 1 and April 30, and people caught with them beyond that date could be fined $67. Studded tires have small metal cleats embedded in the rubber to provide traction on snow and ice.
49-948. RESTRICTIONS AS TO TIRE EQUIPMENT.
(1) Every solid rubber tire on a vehicle shall have rubber on its entire traction surface at least one (1) inch thick above the edge of the flange of the entire periphery.
(2) No person shall operate or move on any highway any motor vehicle, trailer, or semitrailer having any metal tire in contact with the highway.
(3) No tire on a vehicle moved on a highway shall have on its periphery any block, stud, flange, cleat, spike, or any other protuberance of any material other than rubber which projects beyond the tread of the traction surface of the tire, except as allowed herein. It shall be permissible to use farm machinery with tires having protuberances which will not injure the highway, and it shall be permissible to use tire chains. Tires with built-in lugs of tungsten carbide or other suitable material, hereinafter called studs, may be used upon any vehicle when required for safety because of snow, ice, or other conditions tending to cause a vehicle to skid, that will not unduly damage the highway. Motor vehicles, trailers and semitrailers with tires having built-in studs are prohibited on public highways between the dates of May 1 and September 30, annually, except as provided in paragraphs (a), (b) and (c) of this subsection:
- Fire pumper/tanker trucks and ladder trucks belonging to fire departments and firefighting agencies are exempt from the prohibited dates.
- A vehicle may be equipped year-round with tires that have retractable studs if the studs retract pneumatically or mechanically to at or below the wear bar of the tire when not in use and the retractable studs protrude beyond the wear bar of the tire only between October 1 and April 30. Retractable studs may be made of metal or other material and are not subject to the stud weight requirements of subsection (4) of this section.
- Special exemptions from the prohibited dates may be granted by the Idaho transportation board if it is found by the board that enhancements to public safety outweigh the increased pavement wear.
(5) If the Idaho transportation department determines, at any time, that Lookout Pass or Fourth of July Pass on interstate 90 or Lolo Pass on state highway 12 is of an unsafe condition so as to require chains, as defined in section 49-104, Idaho Code, in addition to pneumatic tires, the Idaho transportation department may establish requirements for the use of chains on all commercial vehicles as defined in section 49-123(2)(d)(i) and (ii), Idaho Code, traveling on interstate 90 or state highway 12. If the Idaho transportation department establishes that chains are so required, the Idaho transportation department shall:
- Provide multiple advance notices of the chain requirement;
- Provide adequate opportunities for pull out;
- Provide notification at a point at which the commercial vehicle can safely pull out of the normal flow of traffic, prior to the point at which chains are required; and
- In no case post requirements for chains on bare pavement.
(6) Provided that the conditions in subsection (5) of this section are met, the chain requirement shall be met by chaining a minimum of one (1) tire on each side of:
- One (1) drive axle, regardless of the number of drive axles; and
- One (1) axle at or near the rear of each towed vehicle. Such axle shall not include a variable load suspension axle or an axle of a converter dolly.
(7) Chains as required in subsection (6)(a) and (b) of this section mean “chains” as defined in section 49-104, Idaho Code. Any other traction device differing from chains in construction, material or design but capable of providing traction equal to or exceeding that of chains under similar conditions may be used.
(8) The Idaho transportation department shall place and maintain signs and other traffic control devices on the interstate and state highway passes as designated in subsection (5) of this section that indicate the chain requirements under subsection (6) of this section.