Current through Register Vol. 54, No. 45, November 9, 2024
Section 159.5 - Test procedures(a)Physical dimensions. Tire physical dimensions shall be determined under uniform ambient conditions as follows: (1) Mount the tire on a test rim having the test rim width specified in Appendix A of this chapter for that tire size designation and inflate it to the applicable pressure specified in Table III of Appendix A.(2) Condition it at ambient room temperature for at least 24 hours.(3) Readjust pressure to that specified in paragraph (1).(4) Caliper the section width and overall width at six points approximately equally spaced around the tire circumference.(5) Record the average of these measurements as the section width and overall width, respectively.(6) Determine tire outer diameter by measuring the maximum circumference of the tire and dividing this dimension by pi (3.14).(b)Tubeless tire bead unseating resistance. Bead unseating resistance shall be tested as follows: (1)Preparation of tire-wheel assembly. The tire-wheel assembly shall be prepared as follows: (i) Wash the tire, dry it at the beads, and mount it without lubrication or adhesives on a clean, painted test rim.(ii) Inflate it to the applicable pressure specified in Table III of Appendix A of this chapter at ambient room temperature.(iii) Mount the wheel and tire in the fixture shown in Figure 1 of this section, and force the standard block shown in Figure 2 of this section, against the tire sidewall as required by the geometry of the fixture. Click to view image
(2)Test procedure. The test procedure shall be as follows:(i) Apply a load through the block to the tire outer sidewall at the distance specified in Figure 1 of this section for the applicable wheel size at a rate of two inches per minute, with the load arm substantially parallel to the tire and rim assembly at the time of engagement.(ii) Increase the load until the bead unseats or the applicable value specified in § 159.4(b)(2)(iii) (relating to requirements) is reached.(iii) Repeat the test at least four places equally spaced around the tire circumference.(c)Tire strength. Tire strength shall be tested as follows:(1)Preparation of tire. The tire shall be prepared as follows: (i) mount the tire on a test rim and inflate it to the applicable pressure specified in Table III of Appendix A of this chapter;(ii) condition it at room temperature for at least three hours; and(iii) readjust its pressure to that specified in subparagraph (i).(2)Test procedure. The test procedure shall be as follows: (i) Force a 3/4-inch diameter cylindrical steel plunger with a hemispherical end perpendicularly into the tread rib as near to the centerline as possible, avoiding penetration into the tread groove, at the rate of two inches per minute.(ii) Record the force and penetration at five test points equally spaced around the circumference of the tire. If the tire fails to break before the plunger is stopped by reaching the rim, record the force and penetration as the rim is reached and use these values in subparagraph (iii).(iii) Compute the breaking energy for each test point by means of the following formula: W =Energy, inch-pounds;
F =Force, pounds; and
P =Penetration, inches.
(iv) Determine the breaking energy value for the tire by computing the average of the five values obtained in accordance with subparagraph (iii) of this paragraph.(d)Tire endurance. Endurance shall be tested as follows: (1)Preparation of tire. The tire shall be prepared as follows:(i) Mount a new tire on a test rim and inflate it to the applicable pressure specified in Table III of Appendix A.(ii) Condition the tire assembly to 100°F plus or minus 5°F for at least three hours.(iii) Readjust tire pressure to that specified in subparagraph (i) immediately before testing.(2)Test procedure. The test procedure shall be as follows: (i) Mount the tire and wheel assembly on a test axle and press it against a flat-faced steel test wheel 67.23 inches in diameter and at least as wide as the section width of the tire to be tested or an approved equivalent test wheel, with the applicable test load specified in Table I of Appendix A for the size designation, type, and maximum permissible inflation pressure of the tire.(ii) During the test, the air surrounding the test area shall be 100°F plus or minus 5°F.(iii) Conduct the test at 50 miles per hour in accordance with the following schedule without pressure adjustment or other interruptions: Maximum permissible inflation pressure | Loads for - |
4 hours | 6 hours | 24 hours |
Loads from table I (listed inspecified psi or KPa column) |
32 psi.................................... | 24 | 28 | 32 |
36 psi ................................... | 28 | 32 | 36 |
40 psi ................................... | 32 | 36 | 40 |
240 KPa .............................. | 180 | 220 | 240 |
280 KPa............................... | 220 | 260 | 280 |
300 KPa .............................. | 180 | 220 | 240 |
Load as specified percentage of maximum load rating marked on tire sidewall |
60 psi ................................... | 85 | 92 | 100 |
(iv) Immediately after running the tire the required time, measure its inflation pressure. Allow the tire to cool for one hour. Then deflate the tire, remove it from the test rim, and inspect it for the conditions specified in § 159.4(b)(2)(v)(A) (relating to requirements).(e)High speed performance. High speed performance shall be tested as follows: (1) After preparing the tire in accordance with subsection (d)(1), mount the tire and wheel assembly in accordance with subsection (d)(2)(i) and press it against the test wheel with the load specified in Table I of Appendix A for the size designation of the tire and the applicable pressure specified in Column B of the following table: A | B |
Maximum permissible inflation pressure | Load from Table I |
32 psi ..................................... | 24 |
36 psi ..................................... | 28 |
40 psi ..................................... | 32 |
240 KPa ................................ | 180 KPa column. |
280 KPa ................................ | 220 KPa column. |
300 KPa ................................ | 180 KPa column. |
Load as specified percentage of maximum load rating marked on tire sidewall |
60 psi .................................... | 85 |
(2) Break in the tire by running it for two hours at 50 miles per hour.(3) Allow to cool to 100°F plus or minus 5°F and readjust the inflation pressure to the applicable pressure specified in Table III of Appendix A of this chapter.(4) Without readjusting inflation pressure, test at 75 miles per hour for 30 minutes, 80 miles per hour for 30 minutes, and 85 miles per hour for 30 minutes.(5) Immediately after running the tire the required time, measure its inflation pressure. Allow the tire to cool for one hour. Then deflate the tire, remove it from the test rim, and inspect it for the conditions specified in § 159.4(b)(2)(v)(A).The provisions of this §159.5 amended January 26, 1979, effective 1/27/1979, 9 Pa.B. 346. This section cited in 67 Pa. Code § 159.4 (relating to requirements).