Pneumatic tires

Abstract

A radial ply tire comprises a tread, sidewall and bead regions. At least the region of severe flexing of the sidewall when the tire is run in a deflated or substantially under-inflated condition comprises a rubber compound which has a rebound resilience of at least 87 percent, and more preferably of at least 90 percent, measured by the .[.Lupke.]. .Iadd.Dunlop .Iaddend.pendulum method according to B.S. 903/1950 and a hardness in the range of 45- 65 Shore A.

Having now described my invention, what I claim is: 
     
       1. A radial ply pneumatic tire comprising a tread, a pair of sidewalls each terminating in a tire bead and a carcass of substantially radial cords extending from one tire bead to the other, each sidewall having a highly resilient region disposed axially inwardly and axially outwardly of the carcass and extending radially outwardly from a point radially inward of the maximum width of the tire to the radially outer extremity of the sidewall, the highly resilient region being formed of a high resilient rubber compound having a rebound resilience of at least 87 percent measured by the .[.Lupke.]. .Iadd.Dunlop .Iaddend.pendulum method according to British Standard 903/1950 and a hardness in the range of 45-65 Shore A. 
     
     
       2. A radial ply pneumatic tire according to claim 1 in which the rubber compound has a rebound resilience of at least 90 percent measured by the .[.Lupke.]. .Iadd.Dunlop .Iaddend.pendulum method according to British Standard 903/1950. 
     
     
       3. A radial ply tire according to claim 1 in which the radial cords are provided with a rubber topping compound and the remainder of the rubber in the sidewall consists of the high resilient compound. 
     
     
       4. The tire of claim 1 in which the point from which the high resilient region extends radially outwardly is between one-half and three-quarters of the total length of the sidewall. 
     
     
       5. A radial ply tire according to claim 1 in which the hardness of the high resilient compound is in the range 55-65 Shore A. 
     
     
       6. A radial ply tire according to claim 1 in which the high resilient rubber compound extends into the tires shoulder up to the tread pattern wearable rubber. 
     
     
       7. A radial ply tire according to claim 1 in which the high resilience compound is based on natural rubber. 
     
     
       8. A radial ply tire according to claim 6 in which the high resilience compound extends in the sidewall between the base of the wearable tread pattern rubber and the sidewall immediately radially outward of the rim flange. 
     
     
       9. A radial ply tire according to claim 1 in which the aspect ratio of the tire is in the range 30 to 75 percent. 
     
     
       10. A radial ply tire according to claim 9 in which the aspect ratio is between 55 and 70 percent. 
     
     
       11. A radial ply tire according to claim 1 having a ground contacting surface which is substantially flat. 
     
     
       12. A radial ply tire according to claim 1 in which at least one of the shoulders of the tire is provided with a cushion of high resilience compound inside the tire carcass to thicken the tire in this region. 
     
     
       13. A radial ply tire according to claim 1 having an external buttress of high resilience compound on one or both shoulders of the tire to thicken the tire in this region. 
     
     
       14. In a pneumatic radial tire and wheel assembly capable of being run in a deflated condition having a wheel rim with a pair of opposed annular flanges and means to prevent the tire from becoming dislodged from the wheel when run in a deflated condition; the tire having a pair of sidewalls each terminating in a tire bead and a carcass of substantially radial cords extending from one bead to the other, the improvement comprising means to permit sidewall flexing with low temperature build-up while operating in deflated or low inflation condition, said means comprising two layers of highly resilient material in each sidewall, one layer being disposed axially inwardly and the other being disposed axially outwardly of the carcass, said layers extending radially outwardly from a point radially inward of the maximum axial width of the tire to the radially outer extremity of the sidewall, the layers being formed of a high resilient rubber compound having a rebound resilience of at least 87 percent measured by the .[.Lupke.]. .Iadd.Dunlop .Iaddend.pendulum method according to British Standard 903/1950 and a hardness in the range of 45-65 Shore A. 
     
     
       15. A radial ply pneumatic tire comprising a tread, a pair of sidewalls each terminating in a tire bead with the tread width being greater than the distance between the beads when mounted on a rim and a carcass of substantially radial cords extending from one tire bead to the other, each sidewall having a highly resilient region disposed axially inwardly and axially outwardly of the carcass and extending radially outwardly from a point radially inward of the maximum width of the tire to the radially outer extremity of the sidewall, the highly resilient region being formed of a high resilient rubber compound having a rebound resilience of at least 87 percent measured by the .[.Lupke.]. .Iadd.Dunlop .Iaddend.pendulum method according to British Standard 903/1950 and a hardness in the range of 45-65 Shore A.