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Federal Motor Vehicle Safety Standards; Tires

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Start Preamble

AGENCY:

National Highway Traffic Safety Administration (NHTSA), Department of Transportation.

ACTION:

Final rule; technical amendments; response to petitions for reconsideration.

SUMMARY:

In June 2003, NHTSA published a final rule establishing upgraded tire performance requirements for new tires for use on vehicles with a gross vehicle weight rating of 10,000 pounds or less. In January 2006, NHTSA published a final rule; response to petitions for reconsideration, which modified certain performance requirements to better address snow tires and certain specialty tires. This document responds to a petition for reconsideration of the January 2006 rule. After carefully considering the issues raised, the agency is denying the petition. We are also making a number of technical corrections in several tire-related Federal safety standards.

DATES:

The amendments in this rule are effective September 1, 2007. Voluntary compliance is permitted before that date. If you wish to submit a petition for reconsideration of this rule, your petition must be received October 12, 2007

ADDRESSES:

Petitions for reconsideration should refer to the docket number and be submitted to: Administrator, National Highway Traffic Safety Administration, 1200 New Jersey Avenue, SE., West Building, 4th Floor, Washington, DC 20590. Please see the Privacy Act heading under Regulatory Notices.

Start Further Info

FOR FURTHER INFORMATION CONTACT:

For technical and policy issues, contact George Soodoo, Office of Crash Avoidance Standards, by telephone at (202) 366-2720, or by fax at (202) 366-4329.

For legal issues, contact Rebecca Schade, Office of the Chief Counsel, by telephone at (202) 366-2992, or by fax at (202) 366-3820.

Both persons may be reached by mail at the following address: National Highway Traffic Safety Administration, U.S. Department of Transportation, 1200 New Jersey Avenue, SE., Washington, DC 20590.

End Further Info End Preamble Start Supplemental Information

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Summary of Final Rule; Technical Amendments; Response to Petition for Reconsideration

II. Background

III. Petition for Reconsideration

IV. Discussion and Analysis

V. Technical Corrections to the Regulatory Text

VI. Effective Date

VII. Rulemaking Notices and Analyses

VIII. Regulatory Text

I. Summary of Final Rule; Technical Amendments; Response to Petition for Reconsideration

This final rule makes several technical corrections and amendments to the regulatory text of Federal Motor Vehicle Safety Standard (FMVSS) Nos. 109, 110, 119, and 139, all of which are tire-related standards. This final rule also denies a petition by Advocates for Highway and Auto Safety (Advocates) for reconsideration of the January 2006 final rule; response to petitions for reconsideration, regarding the agency's requirements with respect to the endurance test for snow tires.

II. Background

The Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act, Section 10, “Endurance and resistance standards for tires,” required NHTSA to revise and update FMVSS No. 109, New pneumatic tires, and FMVSS No. 119, New pneumatic tires for vehicles other than passenger cars.[1] In response to this mandate, NHTSA published a final rule on June 26, 2003, establishing FMVSS No. 139, New pneumatic radial tires for light vehicles, which will apply to new tires used on light vehicles; i.e., vehicles with a gross vehicle weight rating (GVWR) of 10,000 pounds or less, except motorcycles and low speed vehicles.[2]

The new standard is scheduled to become effective on September 1, 2007. It features substantially more stringent high speed and endurance tests, and a new low-pressure performance test. The purpose of the new and more stringent requirements is to improve the ability of tires to withstand the effects of tire heat build-up and severe under-inflation during highway travel in fully loaded conditions. Unlike the existing tire safety standards, which previously differentiated between light trucks and passenger cars,[3] FMVSS No. 139 applies to tires used on both.

In a January 2006 final rule; response to petitions for reconsideration,[4] the agency reduced the test speed for the tire endurance and low-inflation pressure performance tests in FMVSS No. 139, paragraphs S6.3.1.2.3 and S6.4.1.2.1, from 120 km/h (75 mph) to 110 km/h (68 mph) for all passenger car snow tires and light truck snow tires with load ranges of C, D, and E. The other test parameters—inflation pressure, duration, load, and ambient temperature—remained unchanged.

For snow tires, the endurance test is a 34-hour test conducted at a speed of 110 km/h (68 mph) with a tire inflation Start Printed Page 49208pressure that is 25 percent below the maximum inflation pressure of the tire, and with tire loads of 85 percent, 90 percent, and 100 percent of maximum load. After the snow tire has completed the endurance test, it is then subjected to a new low pressure test for 90 minutes at an inflation pressure about 42 percent below the tire's maximum inflation pressure at a test speed of 110 km/h (68 mph) with 100 percent of maximum load. The snow tire must complete both the endurance test and the low-inflation pressure test without any failures.

The agency made these changes because of practicability concerns. Snow tires are designed with more flexible (i.e., softer rubber) tread compounds, which are good for finding traction in snow but can pose difficulties for passing certain tire performance tests, because the tread designs and compounds are less able than other tires to withstand the heat caused by the severity of testing on the road wheel. NHTSA determined that the technical design challenges and the costs to redesign existing snow tires to pass the new 120 km/h (75 mph) test would far outweigh the negligible safety benefits associated with that redesign.

The final rule also changed the effective date from June 1 to September 1, 2007, to correspond with the start of the industry model year, and to September 1, 2008 for snow tires.

III. Petition for Reconsideration

NHTSA received one petition for reconsideration from Advocates for Highway and Auto Safety (Advocates) on the January 2006 final rule; response to petitions for reconsideration.[5]

Advocates petitioned the agency to reconsider the revised requirements related to the endurance test for snow tires in FMVSS No. 139. According to Advocates, millions of motorists travel with dedicated snow tires at high speeds on what are often clear roads, free of snow and ice. The petition stated that recent speed studies show that increasing percentages of drivers regularly exceed even Interstate speed limits posted at 75 miles per hour. Advocates argued that instead of requiring manufacturers to improve their snow tire design and performance to better withstand the high speeds and temperatures commonly encountered in high-speed travel on U.S. highways, NHTSA has “grandfathered” existing snow tire safety design and performance by reducing compliance requirements. Advocates disagreed that this decision by the agency meets the intent of the TREAD Act.

IV. Discussion and Analysis

Currently, the endurance test for passenger car snow tires, included in FMVSS No. 109, New pneumatic tires, is conducted at a test speed of 80 km/h (50 mph). For light truck (LT) snow tires, the current endurance test is included in FMVSS No. 119, New pneumatic tires for vehicles other than passenger cars, and is conducted at a test speed of 80 km/h (50 mph) for load range “C” and “D” tires, and at 64 km/h (40 mph) for load range “E” tires. The change in endurance test speed to 110 km/h (68 mph) in the new FMVSS No. 139 is a speed increase of 38 percent for passenger car snow tires and LT snow tires load ranges C and D, and 72 percent for LT snow tires load range E. These changes represent a substantial increase in the stringency of the endurance test from the current standards.

FMVSS No. 109 also includes a high speed test for all passenger car tires, including snow tires, with test speeds of 121 km/h (75 mph), 129 km/h (80 mph), and 137 km/h (85 mph), for 30 minutes at each speed step. LT tires, including snow tires, are not currently subject to the requirements of a high speed test under FMVSS No. 119. FMVSS No. 139 includes a high speed test for all light vehicle tires, including snow tires, at test speeds of 140 km/h (87 mph), 150 km/h (93 mph), and 160 km/h (99 mph), for 30 minutes at each speed step.[6] These changes also represent a substantial increase in the stringency of the high speed test from the current standards.

In the final rule; response to petitions for reconsideration, NHTSA explained its determination that because of the nature of snow tire construction, the test speed specified in the June 2003 final rule for the endurance and low-inflation pressure tests [7] created practicability problems for these tires. Snow tires usually feature higher hysteretic tread compounds,[8] molded in greater tread depths and smaller tread blocks than non-snow tires. This construction is used to provide special performance in snow conditions.[9]

These tread designs and compounds are disproportionately affected at high speeds when tested on a laboratory road wheel. Research conducted by the ASTM International has shown that tires tested on a curved road wheel experience an increase in severity (in terms of stress and temperature) of about 12 percent compared to on a flat roadway. A snow tire that experiences chunking [10] from a 120 km/h (75 mph) road wheel test does so in part because of the relative severity of the road wheel as compared to the conditions on a flat roadway at the same speed.

The purpose of the endurance test is to evaluate the tire's performance for an extended time period. The test is conducted at loads of 85 percent of the tire's maximum load rating for 4 hours, at 90 percent for 6 hours, and at 100 percent for another 24 hours, for a total test time of 34 hours. In addition, the test inflation pressure is set at 25 percent below the tire's maximum inflation pressure. These are severe conditions for loading and under-inflation, especially given that a 100-percent load on the test road-wheel equals about a 112-percent load on a flat surface. From a real world perspective, this means that for the last 24 hours of the test, the tire is 12 percent overloaded and 25 percent under-inflated at a test speed of 110 km/h (68 mph). Moreover, the ambient temperature for the endurance test is ­38 °C (100 °F).

Following the endurance test, the snow tire is subjected to a low pressure test, which is a new test for light vehicle tires. The purpose of the low pressure test is to ensure that the tire can be operated for 90 minutes at a speed of 110 km/h (68 mph), at an inflation pressure about 42 percent below the tire's maximum inflation pressure, with a load of 100 percent of the tire's maximum load rating.

FMVSS No. 139 also includes a 90-minute high speed test at speeds of 140 km/h (87 mph), 150 km/h (93 mph), and 160 km/h (99 mph) for all tires to which the standard applies, including snow tires. The purpose of the high speed test Start Printed Page 49209is to evaluate the tire's performance during high speed operation, which makes this test more directly related to the high speed driving to which Advocates referred in its petition. The high speed test parameters also include a load of 85 percent, and an inflation pressure of about 10 percent below the tire's maximum inflation pressure. This test is the same for all light vehicle tires, including snow tires.

Snow tires are generally operated on vehicles during the winter season when ambient temperatures are below 10 °C (50 °F). This real world ambient temperature is considerably lower than the ambient test temperature of 38 °C (100 °F); i.e., the test condition is much more stringent than the likely real world condition. NHTSA believes that the upgraded high speed and endurance tests, and the new low pressure test in FMVSS No. 139, represent a significant increase in performance for light vehicle snow tires as compared to the requirements in FMVSSs No. 109 and 119.

Agency decision: NHTSA has decided to deny the petition from Advocates to increase the test speed for the endurance and low-inflation pressure performance tests for snow tires from 110 km/h (68 mph) to 120 km/h (75 mph).

As originally drafted, the test speed for these two tests was set at 120 km/h (75 mph). Based on analysis of agency research and testing, as well as testing conducted by industry groups and Transport Canada, NHTSA reduced the test speed from 120 km/h (75 mph) to 110 km/h (68 mph) for all passenger car snow tires and LT snow tires with load ranges of C, D, and E. As the response to petitions for reconsideration described, “The technical design challenges and the costs to redesign existing snow tires to pass the 120 km/h (75 mph) test would far outweigh the negligible safety benefits associated with that redesign. By reducing the * * * test speeds from 120 km/h (75 mph) to 110 km/h (68 mph) * * * we can ensure virtually all the safety benefits from upgrading the test speed for snow tires and eliminate practicability and cost concerns.” [11]

The agency believes that this decision is sound. Advocates provided no data to support its argument that changing the test speed from 120 km/h (75 mph) to 110 km/h (68 mph) for snow tires would result in reduced safety for the public when motorists operate their vehicles with snow tires at high speeds for long periods of time. Advocates focused on the endurance test, but did not mention that FMVSS No. 139 includes an upgraded high speed test with speeds up to 160 km/h (99 mph). The endurance test, moreover, assesses the long-term durability of the tire when tested on the road-wheel for 34 hours straight in a significantly under-inflated condition.

The snow tires that NHTSA tested to the endurance and low pressure performance tests in FMVSS No. 139 experienced primarily chunking failures on the curved test road-wheel. Chunking, defined as the breaking away of pieces of the tread or sidewall rubber, occurs during testing on the curved road-wheel because the road-wheel heats the tire by deflecting its outer edges more than would typically occur when tested on a flat surface. In addition, the tread compound, the greater tread depth, and the smaller tread blocks used on snow tires make them more susceptible to chunking failures.

NHTSA believes that the combination of tests in FMVSS No. 139, which tests at increased stress and higher temperatures due to road-wheel curvature—the upgraded high speed test, the upgraded endurance test, and the new low pressure test—represents increases in test severity for snow tires that will result in overall enhanced performance as compared to the current levels of testing. Therefore, NHTSA believes that the rule clearly meets the intent of the TREAD Act, which directed NHTSA to revise and update FMVSS Nos. 109 and 119.

V. Technical Corrections to the Regulatory Text

1. The agency believes that the tire safety standards should be clear and as consistent as possible with one another. FMVSS No. 110 uses the terms “light truck (LT) tire” and “passenger car tire” without specifically defining them. Therefore, FMVSS No. 110 is being amended to add the same definitions for “light truck (LT) tire” and “passenger car tire” as are used in FMVSS No. 139.

2. In the June 2003 final rule, the agency included a new paragraph S4.2.2.3(b) in FMVSS No. 110, stating that “For vehicles equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.” The National Association of Trailer Manufacturers (NATM) and the National Marine Manufacturers Association (NMMA) submitted a “petition for clarification” to the agency requesting confirmation that S4.2.2.3(b) was not intended to apply to trailers. The agency agrees that it was not intended to apply to trailers, which typically have no designated seating positions. We note that the definition of “vehicle normal load on the tire” in S3 of FMVSS No. 110 states that “* * * load on an individual tire * * * is determined by distributing to each axle its share of the curb weight, accessory weight, and normal occupant weight (distributed in accordance with Table I) and divid[ed] by 2.” We believe that the inclusion of “normal occupant weight” in the definition of vehicle normal load on a tire is an indication that S4.2.2.3(a) and (b) do not apply to trailers. To make the standard clearer, the agency is amending S4.2.2.3(a) and (b) of FMVSS No. 110 to exclude trailers that have no designated seating positions from the category of vehicles to which the paragraph applies.

3. In the January 2006 final rule, the agency sought to make clear that temporary spare tires would not be subject to the requirements of the new FMVSS No. 139 (but would instead continue to be subject to the requirements of FMVSS No. 109), by removing references to T-type temporary spare tires from the regulatory text of FMVSS No. 139. To better clarify this, the agency is amending S2, Application, of FMVSS No. 109 to include T-type temporary spare tires; the first sentence of S4.1(a) of FMVSS No. 110 to state that T-type temporary spare tires are subject to FMVSS No. 109; and S2.1, Application, of FMVSS No. 139 to exclude T-type temporary spare tires.

4. Since the January 2006 final rule was published, the agency has identified several typographical errors in Tables II and III of FMVSS No. 119, and is therefore revising and republishing the tables to correct those mistakes.

5. In the January 2006 final rule, FMVSS No. 139 was amended to remove references to CT tires because those tires are no longer being offered for sale in the United States. Because the January 2006 final rule failed to also make conforming changes to S3, Definitions, and S5.2, Performance requirements, of FMVSS No. 139, the agency is now amending those paragraphs to remove other references to CT tires.

6. In the January 2006 final rule, subparagraph (i) was added to S5.5, Tire markings of FMVSS No. 139, to specify requirements for snow tires marked with the “alpine symbol.” Because the January 2006 final rule failed to also make a conforming change to the introductory paragraph of S5.5, the agency is now amending that paragraph Start Printed Page 49210to account for this additional subparagraph.

7. A number of typographical errors were found throughout S6, Test procedures, conditions, and performance requirements, of FMVSS No. 139, and are being corrected in this final rule.

VI. Effective Date

The effective date of these amendments is September 1, 2007.

VII. Rulemaking Notices and Analyses

This rule makes a number of technical corrections to the regulatory text of several Federal tire safety regulations, and has no impact on the regulatory burden of manufacturers. The agency discussed the relevant requirements of Executive Order 12866, the Department of Transportation's regulatory policies and procedures, the Regulatory Flexibility Act, the National Environmental Policy Act, Executive Order 13132 (Federalism), the Unfunded Mandates Act, Civil Justice Reform, the National Technology Transfer and Advancement Act, and the Paperwork Reduction Act in the June 2003 and January 2006 final rules cited above. Those discussions are not affected by these technical amendments.

Privacy Act

Please note that anyone is able to search the electronic form of all documents received into any of our dockets by the name of the individual submitting the document (or signing the document, if submitted on behalf of an association, business, labor union, etc.). You may review DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (Volume 65, Number 70; Pages 19477-78), or you may visit http://dms.dot.gov.

VIII. Regulatory Text

Start List of Subjects

List of Subjects in 49 CFR Part 571

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In consideration of the foregoing, part 571 is amended as follows:

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PART 571—FEDERAL MOTOR VEHICLE SAFETY STANDARDS

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1. The authority citation for part 571 continues to read as follows:

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Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166; delegation of authority at 49 CFR 1.50.

End Authority Start Amendment Part

2. Section 571.109 is amended by revising S2 to read as follows:

End Amendment Part
Standard No. 109—New pneumatic and certain specialty tires.
* * * * *

S2 Application. This standard applies to new pneumatic radial tires for use on passenger cars manufactured before 1975, new pneumatic bias ply tires, T-type spare tires, ST, FI, and 8-12 rim diameter and below tires for use on passenger cars manufactured after 1948. However, it does not apply to any tire that has been so altered so as to render impossible its use, or its repair for use, as motor vehicle equipment.

* * * * *
Start Amendment Part

3. Section 571.110 is amended by adding to S3, in alphabetical order, new definitions of “Light truck (LT) tire” and “Passenger car tire”, and revising S4.1 and S4.2.2.3, to read as follows:

End Amendment Part
Standard No. 110; Tire selection and rims for motor vehicles with a GVWR of 4,536 kilograms (10,000 pounds) or less.
* * * * *

S3 Definitions.

* * * * *

Light truck (LT) tire means a tire designated by its manufacturer as primarily intended for use on lightweight trucks or multipurpose passenger vehicles.

* * * * *

Passenger car tire means a tire intended for use on passenger cars, multipurpose passenger vehicles, and trucks, that have a gross vehicle weight rating (GVWR) of 10,000 pounds or less.

* * * * *

S4.1 General. Vehicles shall be equipped with tires that meet the requirements of § 571.139, New pneumatic tires for light vehicles, except that passenger cars may be equipped with a pneumatic T-type temporary spare tire assembly that meets the requirements of § 571.109, or equipped with a non-pneumatic spare tire assembly that meets the requirements of § 571.129, New non-pneumatic tires for passenger cars, and S6 and S8 of this standard. Passenger cars equipped with a non-pneumatic spare tire assembly shall meet the requirements of S4.3(e), and S5, and S7 of this standard.

* * * * *

S4.2.2.3 (a) For vehicles, except trailers with no designated seating positions, equipped with passenger car tires, the vehicle normal load on the tire shall be no greater than 94 percent of the derated load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.

(b) For vehicles, except trailers with no designated seating positions, equipped with LT tires, the vehicle normal load on the tire shall be no greater than 94 percent of the load rating at the vehicle manufacturer's recommended cold inflation pressure for that tire.

* * * * *
Start Amendment Part

4. Section 571.119 is amended by revising Tables II and III to read as follows:

End Amendment Part
Standard No. 119; New pneumatic tires for motor vehicles with a GVWR of more than 4,536 kilograms (10,000 pounds) and motorcycles.
* * * * *
Start Printed Page 49211

Table II.—Minimum Static Breaking Energy

[Joules (J) and Inch-Pounds (inch-lbs)]

Tire characteristicMotorcycleAll 12 rim diameter code or smaller except motorcycleLight truck and 17.5 rim diameter code or smaller TubelessTires other than Light Truck, Motorcycle, 12 rim diameter code or smaller
Tube typeTubeless greater than 17.5 rim diameter codeTube typeTubeless greater than 17.5 rim diameter code
Plunger diameter (mm and inches)7.94 mm5/16″19.05 mm3/4″19.05 mm3/4″31.75 mm11/4″31.75 mm11/4″38.10 mm11/2″38.10 mm11/2″
Breaking EnergyJIn-lbsJIn-lbsJIn-lbsJIn-lbsJIn-lbsJIn-lbsJIn-lbs
Load Range:
A16150676002252,000
B333001351,2002932,600
C454002031,8003613,2007686,8005765,100
D2712,4005144,5508927,9007346,500
E3383,0005765,1001,41212,5009718,600
F4063,6006445,7001,78515,8001,41212,500
G7116,3002,28220,2001,69415,000
H7686,8002,59823,0002,09018,500
J2,82425,0002,20319,500
L3,05027,000
M3,22028,500
N3,38930,000

Table III.—Endurance Test Schedule

DescriptionLoad rangeTest wheel speedTest load: Percent of maximum load ratingTotal test revolutions (thousands)
km/hr/mI-7 hoursII-16 hoursIII-24 hours
Speed restricted service:
90 km/h (55 mph)F, G, H, J, L, M, N401256684101352.0
80 km/h (50 mph)F, G, H, J, L321006684101282.5
56 km/h (35 mph)All24756684101211.0
MotorcycleAll802501 1002 108117510.0
All otherF642006684101564.0
G561756684101493.5
H, J, L, N481506684101423.5
* * * * *
Start Amendment Part

5. Section 571.139 is amended by revising S2.1; S3; S5.2(c); S5.5; S5.5.4; S6.1.1.1.5; S6.1.2; S6.2.1.1.2; S6.4.1.1.2; and S6.6 to read as follows:

End Amendment Part
Standard No. 139; New pneumatic radial tires for light vehicles.
* * * * *

S2.1 Application. 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 8 inches and below, or T-type temporary use spare tires with radial construction.

* * * * *

S3 Definitions.

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.

Light truck (LT) tire means a tire designated by its manufacturer as primarily intended for use on lightweight trucks or multipurpose passenger vehicles.

Load rating means the maximum load that a tire is rated to carry for a given inflation pressure.

Maximum load rating means the load rating for a tire at the maximum permissible inflation pressure for that tire.

Maximum permissible inflation pressure means the maximum cold inflation pressure to which a tire may be inflated.

Measuring rim means the rim on which a tire is fitted for physical dimension requirements.

Open splice means any parting at any junction of tread, sidewall, or innerliner that extends to cord material.

Outer diameter means the overall diameter of an inflated new tire. Start Printed Page 49212

Overall width means the linear distance between the exteriors of the sidewalls of an inflated tire, including elevations due to labeling, decorations, or protective bands or ribs.

Passenger car tire means a tire intended for use on passenger cars, multipurpose passenger vehicles, and trucks, that have a gross vehicle weight rating (GVWR) of 10,000 pounds or less.

Ply means a layer of rubber-coated parallel cords.

Ply separation means a parting of rubber compound between adjacent plies.

Pneumatic tire means a mechanical device made of rubber, chemicals, fabric and steel or other materials, that, when mounted on an automotive wheel, provides the traction and contains the gas or fluid that sustains the load.

Radial ply tire means a pneumatic tire in which the ply cords that extend to the beads are laid at substantially 90 degrees to the centerline of the tread.

Reinforced tire means a tire designed to operate at higher loads and at higher inflation pressures than the corresponding standard tire.

Rim means a metal support for a tire or a tire and tube assembly upon which the tire beads are seated.

Section width means the linear distance between the exteriors of the sidewalls of an inflated tire, excluding elevations due to labeling, decoration, or protective bands.

Sidewall means that portion of a tire between the tread and bead.

Sidewall separation means the parting of the rubber compound from the cord material in the sidewall.

Test rim means the rim on which a tire is fitted for testing, and may be any rim listed as appropriate for use with that tire.

Tread means that portion of a tire that comes into contact with the road.

Tread rib means a tread section running circumferentially around a tire.

Tread separation means pulling away of the tread from the tire carcass.

Treadwear indicators (TWI) means the projections within the principal grooves designed to give a visual indication of the degrees of wear of the tread.

Wheel-holding fixture means the fixture used to hold the wheel and tire assembly securely during testing.

* * * * *

S5.2 Performance requirements. Each tire shall conform to each of the following:

* * * * *

(c) Its maximum permissible inflation pressure shall be 240, 280, 300, 340, or 350 kPa.

* * * * *

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. The markings must be in letters and numerals not less than 0.078 inches high and raised above or sunk below the tire surface not less than 0.015 inches.

* * * * *

S5.5.4 For passenger car tires, if the maximum inflation pressure of a tire is 240, 280, 300, 340, or 350 kPa, then:

(a) Each marking of that inflation pressure pursuant to S5.5(c) must be followed in parenthesis by the equivalent psi, rounded to the next higher whole number; and

(b) Each marking of the tire's maximum load rating pursuant to S5.5(d) in kilograms must be followed in parenthesis by the equivalent load rating in pounds, rounded to the nearest whole number.

* * * * *

S6.1.1.1.5 Readjust the tire pressure to that specified in S6.1.1.1.2.

* * * * *

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.

* * * * *

S6.2.1.1.2 Condition the assembly at 32 to 38 °C for not less than 3 hours.

* * * * *

S6.4.1.1.2 After the tire is deflated to the appropriate test pressure in S6.4.1.1.1 at the completion of the endurance test, condition the assembly at 32 to 38 °C for not less than 2 hours.

* * * * *

S6.6 Tubeless tire bead unseating resistance. Each tire shall comply with the requirements of S5.2 of § 571.109. For light truck tires, the maximum permissible inflation pressure to be used for the bead unseating test is as follows:

Load Range C260 kPa.
Load Range D340 kPa.
Load Range E410 kPa.

For light truck tires with a nominal cross section greater than 295 mm (11.5 inches), the maximum permissible inflation pressure to be used for the bead unseating test is as follows:

Load Range C190 kPa.
Load Range D260 kPa.
Load Range E340 kPa.
* * * * *
Start Signature

Issued: August 22, 2007.

Stephen R. Kratzke,

Associate Administrator for Rulemaking.

End Signature End Supplemental Information

Footnotes

1.  Pub. L. 106-414, November 1, 2000, 114 Stat. 1800.

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2.  68 FR 38115 (June 26, 2003); Docket No. NHTSA-2003-15400.

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3.  

Historically, FMVSS No. 109 applied to tires for passenger cars, and FMVSS No. 119 applied to tires for use on all other vehicles, including light trucks. Back to Citation

4.  71 FR 877 (Jan. 6, 2006); Docket No. NHTSA-2005-23439.

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5.  Docket No. NHTSA-2006-23439-3.

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6.  We note that the miles per hour (mph) values listed in this sentence are not included in the regulatory text of FMVSS No. 139, which lists only the metric speed values in S6.2.1.2.7.

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7.  The June 2003 final rule for FMVSS No. 139 also added a brand-new low-inflation pressure performance test, which no standard had previously contained. As a brand-new test, that addition to FMVSS No. 139 also represented a rise in the stringency of the standard over the current standards.

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8.  In plainer English, this means that since snow tires are designed to operate in low ambient temperatures, the tread compound tends to be softer to enhance traction. Because it is softer and more pliable, as opposed to harder and more durable (like normal road tires), the tread compound is less able to withstand the high temperatures experienced on the road wheel during testing, which leads to pieces of tread rubber chunking off the tire.

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9.  Deeper treads with smaller surface areas contacting the ground help in snow (and other low traction situations) because they are able to push deeper through the snow to find traction—not entirely unlike, for example, the advantage of wearing shoes with cleats on a wet sports field.

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10.  “Chunking” is defined as the breaking away of pieces of the tread or sidewall rubber.

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11.  71 FR 880 (Jan. 6, 2006).

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[FR Doc. E7-16934 Filed 8-27-07; 8:45 am]

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