Evaluation of Laboratory Tire Tread and Sidewall Strength (Plunger Energy) Test Methods

Under the TREAD Act, National Highway Traffic Safety Administration (NHTSA) was assigned the task of revising and updating the Federal Motor Vehicle Safety Standards (FMVSS) for tires. This effort included research to support a possible update or replacement of the tire strength test contained in the FMVSS Nos. 109 and 119. The tire strength test was designed in the 1960s to evaluate the strength of the reinforcing materials in bias-ply tires and their resistance to road hazards. In this test, a steel plunger is forced perpendicular to the tread of a mounted and inflated tire until the tire ruptures (with the resulting air loss), or the plunger is stopped by reaching the rim. The plunger penetration distance and the force test points are then used to calculate an average breaking energy that must exceed the required “minimum breaking energy.” For modern radial tires, which have flexible sidewalls and high-strength steel belt packages, the vast majority of plunger strength tests “bottom-out” on the rim before rupturing the tire. One part of the research consisted of testing passenger and light truck tires to the strength test in FMVSS No. 109 or 119 at standard or low inflation pressures in order to evaluate instances of plunger bottom-out. All 12 tires tested to the standard FMVSS Strength Test conditions reached the required minimum breaking energy before either bottoming-out (67%), or rupturing (33%). Of eight additional tires tested at low pressure, the two lowest-aspect-ratio tires did not reach the required minimum breaking energy level before bottoming-out. Additional testing was conducted with the ASTM F414-06 standard, which allows for repeats of the FMVSS Strength Test at increasing increments of inflation pressure in order to generate more force per unit of penetration (i.e., more rapid accumulation of energy to avoid bottom-out). The six tires tested to ASTM F414-06 also reached the FMVSS minimum breaking energy before either bottoming-out (66.6%), or rupturing (16.6%). Four of those six tires transitioned from bottoming-out to rupturing when increasingly higher inflation pressures were used. Two of three additional tires tested at low starting pressures also transitioned from bottoming-out to rupturing when increasingly higher inflation pressures were used. One tire that had exceeded the FMVSS minimum breaking energy requirements at 30 psi test pressure, ruptured below the FMVSS requirement at 38 psi, indicating that extrapolations of energy levels at lower pressures may not always be predictive of a test at a higher pressure. Six passenger tire models were also tested using an experimental sidewall bruise/strength test and generated statistically different levels of bruise width, penetration, and rupture force between 1-, 2-, and 3-ply sidewall tires.

• Record URL:
  http://www.nhtsa.gov/DOT/NHTSA/NVS/Vehicle%20Research%20&%20Test%20Center%20(VRTC)/ca/Tires/811797.pdf
• 
• Corporate Authors:

  National Highway Traffic Safety Administration

  Vehicle Research and Test Center, P.O. Box 37
  East Liberty, OH  United States  43319

  National Highway Traffic Safety Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Harris, John R
  • Evans, Larry R
  • MacIsaac Jr, James D
• Publication Date: 2013-7

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Pagination: 70p

Subject/Index Terms

• TRT Terms: Performance tests; Strength of materials; Test procedures; Tire sidewalls; Tire treads; Tires; Vehicle safety
• Identifier Terms: Federal Motor Vehicle Safety Standards
• Subject Areas: Highways; Vehicles and Equipment; I91: Vehicle Design and Safety;

Filing Info

• Accession Number: 01493220
• Record Type: Publication
• Report/Paper Numbers: DOT HS 811 797
• Contract Numbers: DTNH 22-02-D-08062; 22-03-D-08660; 22-07-D-00060
• Files: HSL, TRIS, ATRI, USDOT
• Created Date: Sep 19 2013 12:16PM