FMVSS 139: New Pneumatic Radial Tires for Light Vehicles explained.

What FMVSS 139 says it is for

The eCFR heads this section "Standard No. 139; New pneumatic radial tires for light vehicles." Under 49 CFR part 571, the Federal Motor Vehicle Safety Standards are the numbered standards that set safety performance requirements for motor vehicles and equipment. The text below is quoted from 571.139 as current through October 29, 2026.

This standard specifies tire dimensions, test requirements, labeling requirements, and defines tire load ratings.

What it applies to

The application section of the standard says:

This standard applies to new pneumatic radial tires for use on motor vehicles (other than motorcycles and low speed vehicles) that have a gross vehicle weight rating (GVWR) of 10,000 pounds or less and that were manufactured after 1975. This standard does not apply to special tires (ST) for trailers in highway service, tires for use on farm implements (FI) in agricultural service with intermittent highway use, tires with rim diameters of 12 inches and below, T-type temporary use spare tires with radial construction, and light truck tires with a tread depth of 18/32 inch or greater.

Applicability is decided by the text of the standard as written, including any exclusions it lists, and by the date-specific rules in it. This page does not decide whether a particular vehicle or item is covered.

How the standard is organized

The eCFR text of 571.139 has these top-level sections:

• S1: Scope and purpose
• S2: Application
• S3: Definitions
• S4: Tire and rim matching information
• S5: General requirements
• S7: Phase-in schedule for tire markings

In all, the text has 36 numbered headings. Use the finder above to search them; for example, a search for "test" lists the headings that mention tests.

Second-level headings at a glance

These are the numbered sub-sections one level below the top, in order (first 12 of 12):

• S5.1 Size and construction
• S5.2 Performance requirements
• S5.3 Test sample
• S5.4 Treadwear indicators
• S5.5 Tire markings
• S6.1 Tire dimensions
• S6.2 High Speed Performance
• S6.3 Tire Endurance
• S6.4 Low Inflation Pressure Performance
• S7.1 Tires manufactured on or after September 1, 2005 and before September 1, 2006
• S7.2 Tires manufactured on or after September 1, 2006 and before September 1, 2007
• S7.3 Tires manufactured on or after September 1, 2007

Key requirements, quoted from the text

These are excerpts from the requirements sections of 571.139, in the order the standard presents them. Long paragraphs are shortened where marked with [...]; the eCFR has the complete text, tables and figures, which this page omits.

S4 Tire and rim matching information. S4.1. Each manufacturer of tires must ensure that a listing of the rims that may be used with each tire that it produces is provided to the public in accordance with S4.1.1 and S4.1.2. S4.1.1 Each rim listing for a tire must include dimensional specifications and a diagram of the rim and must be in one of the following forms: (a) Listed by manufacturer name or brand name in a document furnished to dealers of the manufacturer's tires, to any person upon request, and in duplicate to the Docket Section (No. NHTSA-2009-0117), National Highway Traffic Safety Administration, West Building, 1200 New Jersey Ave. SE, Washington, DC 20590; or (b) Contained in publications, current at the date of manufacture of the tire or any later date, of at least one of the following organizations: (1) The Tire and Rim Association. (2) The European Tyre and Rim Technical Organization. (3) Japan Automobile Tire Manufacturers' Association, Inc. (4) Tyre & Rim Association of Australia. (5) Associacao Latino Americana de Pneus e Aros (Brazil). (6) South African Bureau of Standards. [...]

S5.1 Size and construction. Each tire shall fit each rim specified for its size designation in accordance with S4.1.

S5.2 Performance requirements. Each tire shall conform to each of the following: (a) It shall meet the requirements specified in S6 for its tire size designation, type, and maximum permissible inflation pressure. (b) It shall meet each of the applicable requirements set forth in paragraphs (c) and (d) of this S5.2, when mounted on a model rim assembly corresponding to any rim designated by the tire manufacturer for use with the tire in accordance with S4. (c) Its maximum permissible inflation pressure shall be 240, 280, 300, 340, or 350 kPa. (d) Its load rating shall be that specified either in a submission made by an individual manufacturer, pursuant to S4, or in one of the publications described in S4 for its size designation, type and each appropriate inflation pressure. [...]

S5.3 Test sample. For the tests specified in S6, use: (a) One tire for high speed; (b) Another tire for endurance and low inflation pressure performance; and (c) A third tire for physical dimensions, resistance to bead unseating, and strength, in sequence.

S5.4 Treadwear indicators. Except in the case of tires with a 12-inch or smaller rim diameter, each tire shall have not less than six treadwear indicators spaced approximately equally around the circumference of the tire that enable a person inspecting the tire to determine visually whether the tire has worn to a tread depth of one sixteenth of an inch. Tires with 12-inch or smaller rim diameter shall have not less than three such treadwear indicators.

S5.5 Tire markings. Except as specified in paragraphs (a) through (i) of S5.5, each tire must be marked on each sidewall with the information specified in S5.5(a) through (d) and on one sidewall with the information specified in S5.5(e) through (i) according to the phase-in schedule specified in S7 of this standard. The markings must be placed between the maximum section width and the bead on at least one sidewall, unless the maximum section width of the tire is located in an area that is not more than one-fourth of the distance from the bead to the shoulder of the tire. If the maximum section width falls within that area, those markings must appear between the bead and a point one-half the distance from the bead to the shoulder of the tire, on at least one sidewall. [...]

S5.5.1 Tire identification number. (a) Tires manufactured before September 1, 2009. Each tire must be labeled with the tire identification number required by 49 CFR part 574 on a sidewall of the tire. Except for retreaded tires, either the tire identification number or a partial tire identification number, containing all characters in the tire identification number, except for the date code and, at the discretion of the manufacturer, any optional code, must be labeled on the other sidewall of the tire. (b) Tires manufactured on or after September 1, 2009. Each tire must be labeled with the tire identification number required by 49 CFR part 574 on the intended outboard sidewall of the tire. [...]

S6.1 Tire dimensions. S6.1.1 Test conditions and procedures. S6.1.1.1 Tire Preparation. S6.1.1.1.1 Mount the tire on the measuring rim specified by the tire manufacturer or in one of the publications listed in S4.1.1 S6.1.1.1.2 For passenger car tires, inflate to the pressure specified in the following table:

S6.1.1.2 Test procedure. S6.1.1.2.1 Measure the section width and overall width by caliper at six points approximately equally spaced around the circumference of the tire, avoiding measurement of the additional thickness of the special protective ribs or bands. The average of the measurements so obtained are taken as the section width and overall width, respectively. S6.1.1.2.2 Determine the outer diameter by measuring the maximum circumference of the tire and dividing the figure so obtained by Pi (3.14).

S6.1.2 Performance Requirements. The actual section width and overall width for each tire measured in accordance with S6.1.1.2 shall not exceed the section width specified in a submission made by an individual manufacturer, pursuant to S4.1.1(a) or in one of the publications described in S4.1.1(b) for its size designation and type by more than: (a) (For tires with a maximum permissible inflation pressure of 32, 36, or 40 psi) 7 percent, or (b) (For tires with a maximum permissible inflation pressure of 240, 280, 300, 340 or 350 kPa) 7 percent or 10 mm (0.4 inches), whichever is larger.

S6.2 High Speed Performance. S6.2.1 Test conditions and procedures. S6.2.1.1 Preparation of tire. S6.2.1.1.1 Mount the tire on a test rim and inflate it to the pressure specified for the tire in the following table:

S6.2.1.1.2 Condition the assembly at 32 to 38 °C for not less than 3 hours. S6.2.1.1.3 Before or after mounting the assembly on a test axle, readjust the tire pressure to that specified in S6.2.1.1.1. S6.2.1.2 Test procedure.

S6.2.1.2.3 Break-in the tire by running it for 2 hours at 80 km/h. S6.2.1.2.4 Allow tire to cool to 38 °C and readjust inflation pressure to applicable pressure in 6.2.1.1.1 immediately before the test. S6.2.1.2.5 Throughout the test, the inflation pressure is not corrected and the test load is maintained at the value applied in S6.2.1.2.2. S6.2.1.2.6 During the test, the ambient temperature, measured at a distance of not less than 150 mm and not more than 1 m from the tire, is maintained at not less than 32 °C or more than 38 °C. S6.2.1.2.7 The test is conducted, continuously and uninterrupted, for ninety minutes through three thirty-minute consecutive test stages at the following speeds: 140, 150, and 160 km/h. S6.2.1.2.8 Allow the tire to cool for between 15 minutes and 25 minutes. Measure its inflation pressure. [...]

S7.1 Tires manufactured on or after September 1, 2005 and before September 1, 2006. For tires manufactured on or after September 1, 2005 and before September 1, 2006, the number of tires complying with S4, S5.5, S5.5.1, S5.5.2, S5.5.3, S5.5.4, S5.5.5, and S5.5.6 of this standard must be equal to not less than 40% of the manufacturer's production during that period.

S7.2 Tires manufactured on or after September 1, 2006 and before September 1, 2007. For tires manufactured on or after September 1, 2006 and before September 1, 2007, the number of tires complying with S4, S5.5, S5.5.1, S5.5.2, S5.5.3, S5.5.4, S5.5.5, and S5.5.6 of this standard must be equal to not less than 70% of the manufacturer's production during that period.

S7.3 Tires manufactured on or after September 1, 2007. Each tire must comply with S4, S5.5, S5.5.1, S5.5.2, S5.5.3, S5.5.4, S5.5.5, and S5.5.6 of this standard.

Defined terms

The standard defines 37 terms in its definitions section; the first 12 are quoted here from the eCFR.

• Bead means the part of the tire that is made of steel wires, wrapped or reinforced by ply cords and that is shaped to fit the rim.
• Bead separation means a breakdown of the bond between components in the bead.
• Bias ply tire means a pneumatic tire in which the ply cords that extend to the beads are laid at alternate angles substantially less than 90 degrees to the centerline of the tread.
• Carcass means the tire structure, except tread and sidewall rubber which, when inflated, bears the load.
• Chunking means the breaking away of pieces of the tread or sidewall.
• Cord means the strands forming the plies in the tire.
• Cord separation means the parting of cords from adjacent rubber compounds.
• Cracking means any parting within the tread, sidewall, or inner liner of the tire extending to cord material.
• Extra load tire means a tire designed to operate at higher loads and higher inflation pressure than the corresponding standard tire.
• Groove means the space between two adjacent tread ribs.
• Innerliner means the layer(s) forming the inside surface of a tubeless tire that contains the inflating medium within the tire.
• Innerliner separation means the parting of the innerliner from cord material in the carcass.

Limits of this page

This page quotes the text of 49 CFR 571.139 as published in the eCFR, current through October 29, 2026. It omits tables, figures, cross-referenced test procedures in other parts, and the preambles and rulemaking history that explain the rule. It does not tell you whether a given vehicle, part or product complies, how to run a test, or what a manufacturer must certify. Compliance questions go to the manufacturer's engineers, qualified counsel or NHTSA. The eCFR is an editorial compilation, not the official legal edition of the Federal Register.

Sources

Sources opened and read November 2, 2026.

• eCFR: 49 CFR 571.139, Standard No. 139; New pneumatic radial tires for light vehicles. (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR part 571, Federal Motor Vehicle Safety Standards (current through October 29, 2026) (read November 2, 2026)