Method for testing the resistance of a tyre to pressure loss

1. A method for testing a resistance of a tyre to a loss in pressure following puncturing of the tyre, the method comprising steps of:

creating a plurality of punctures in a wall of the tyre by inserting a plurality of puncturing objects through the wall;

running the tyre with the puncturing objects in the wall thereof over a given distance;

regulating an inflation pressure of the tyre during the running step;

stopping the running of the tyre; and,

after completing the running step, determining, for each puncture, a pressure loss resistance index based on an estimate of a leak rate of the puncture,

wherein the puncturing objects are ejectable from the wall of the tyre during the running step, and

wherein the puncturing objects include a combination of 8 to 30 screws and nails of different diameters.

2. The test method according to claim 1 , further comprising a step of, when the tyre does not include any self-sealing product, after the stopping step and prior to the determining step, placing a sealing product in an internal cavity of the tyre.

3. The test method according to claim 1 , wherein, when at least one of the puncturing objects has remained in place during the running step, for each puncture corresponding to a puncturing object that has remained in place during the running step, a pressure loss resistance with the puncturing object in place index (I P ) is determined based on an estimate of a leak rate.

4. The test method according to claim 1 , wherein, when at least one of the puncturing objects has been ejected from the wall of the tyre during the running step, for each puncture corresponding to a puncturing object that has been ejected during the running step, a pressure loss resistance after ejection of the puncturing object index (I E ) is determined based on an estimate of a leak rate.

5. The test method according to claim 1 , further comprising steps of, after the running step:

extracting each puncturing object still in place after the running step; and

determining, for each puncture corresponding to a puncturing object that has been ejected during the running step or that has been extracted in the extracting step, a pressure loss resistance index (I E ) based on an estimate of a leak rate.

6. The test method according to claim 1 , further comprising a step of redetermining, after a given time of 5 to 20 minutes, for each puncture corresponding to a puncturing object that has been ejected during the running step or that has been extracted after the running step, a pressure loss resistance index (I 10 ) based on an estimate of a leak rate.

7. The test method according to claim 1 , further comprising a step of calculating a mean pressure loss resistance index (I M ) for all punctures.

8. The test method according to claim 1 , wherein, during the running step, the tyre is run a distance greater than 200 km.

9. The test method according to claim 1 , wherein, during the running step, the tyre is run on a rolling road.

10. The test method according to claim 9 , wherein a developed length of the rolling road is greater than 16 m.

11. The test method according to claim 1 , wherein the tyre is inflated before the puncturing objects are inserted through the wall of the tyre.

12. The test method according to claim 1 , wherein the regulated inflation pressure during the running step is a pressure between 1.8 and 3 bar.

13. The test method according to claim 1 , wherein, during the running step, the tyre is run at a speed in a range of 90 km/h to 160 km/h.

14. The test method according to claim 13 , wherein, during the running step, the speed varies in steps of increasing speed.

15. The test method according to claim 5 , further comprising steps of, after the running step, after the extracting step, and after the determining step:

running the tyre in an inflated condition for an additional distance without a puncturing object in place; and

determining, for each puncture, a pressure loss resistance index based on an estimate of a leak rate.

16. The test method according to claim 15 , wherein, during the additional distance run by the tyre is between 100 and 500 km.

17. The test method according to claim 1 , wherein a diameter of at least one of the puncturing objects is from 1 to 5 mm.

18. The test method according to claim 1 , wherein at least one of the puncturing objects is inserted through a crown portion of the tyre.

19. The test method according to claim 18 , wherein the at least one of the puncturing objects is inserted through the crown portion of the tyre from an exterior surface of grooves of a tread pattern of the tyre.

20. The test method according to claim 18 , wherein the at least one of the puncturing objects is inserted through the crown portion of the tyre from an exterior surface of a tread block of a tread pattern of the tyre.

21. The test method according to claim 1 , further comprising a step of using a surfactant to visualize and qualitatively assess a leak rate of a puncture.

22. The test method according to claim 21 , wherein a scoring scheme is used to assess the leak rate of a puncture, in which

a score of 100 corresponds to no leak, with no bubble visible;

a score of 80 corresponds to a nanoleak, with very small bubbles having a diameter smaller than 0.1 mm and visible only with a magnifying glass;

a score of 60 corresponds to a microleak, with small bubbles having diameters between 0.1 and 1 mm and visible by naked eye; and

a score of 0 corresponds to a leak, with growing bubbles having a diameter greater than 1 mm, with or no bubble at all due to an excessive air flow rate.

23. The test method according to claim 1 , further comprising a step of determining an overall index by combining scores corresponding to the puncturing objects and weighting the scores using a curve that indicates a frequency at which the puncturing objects appear within a customer base.