GB2053815A

GB2053815A - Pneumatic safety tire

Info

Publication number: GB2053815A
Application number: GB8017575A
Authority: GB
Original assignee: Goodyear Tire and Rubber Co
Current assignee: Goodyear Tire and Rubber Co
Priority date: 1979-06-06
Filing date: 1980-05-29
Publication date: 1981-02-11
Also published as: JPS55164510A; ZA802710B; AT381476B; GB2053815B; ATA241480A; FR2458407B1; JPS595444B2; BR8003227A; DE3017461A1; FR2458407A1; CA1126635A; IT8022583A0; AR220839A1; AU530898B2; AU5812480A; LU82499A1; IT1131281B

Abstract

A pneumatic safety tire 10 capable of being used in the uninflated condition at a speed up to a maximum predetermined value for a maximum predetermined distance which can then be repaired and returned to normal service, comprises sidewalls 14, 16 which have a configuration such that the bending moment stresses experienced in the sidewall when the tire is operated in the uninflated state do not exceed a predetermined value. The portion 46,48 of the sidewall radially and axially inward of the carcass ply structure 30 is made of an elastomeric material having a dynamic modulus at least equal to or greater than 50 kg/cm<2> and has a ratio of hysteresis to dynamic modulus less than or equal to 24% kg/cm<2>. <IMAGE>

Description

SPECIFICATION Pneumatic safety tire The foregoing abstract is not to be taken as limiting the invention of this application, and in order to understand the full nature and extend of the technical nature of this application, reference must be made to the accompanying drawings and the following detailed description.

Background of the invention This invention relates to a tire; more particularly, to an improved pneumatic tire capable of being used in the uninflated condition.

Various tire contructions have been suggested which are capable of being used in the uninflated condition.

One approach taken is to strengthen the sidewall so that the tire can support the vehicle load by itself when in the uninflated state. The sidewalls are generally strengthened by increasing the cross-sectional thickness of the sidewall members by a substantial amount in relationship to the normal thickness. However, due to the large amount of rubber required to stiffen the sidewall members, heat build-up has become a major factor in early tire failure when the tire is operated in the uninflated condition, and to a lesser extent in the underinflated condition.

Brief description of the invention Applicant has discovered an improved tire construction in which the tire's durability during operation in the uninflated condition is improved while at the same time maintaining the desired tire performance in the inflated condition, and which after being used in the uninflated condition at a speed up to a maximum predetermined value for a distance up to a maximum predetermined distance, can be repaired and returned to normal use.

A tire made in accordance with the present invention has a sidewall configuration such that the normal bending stresses experienced in the sidewalls during operation in the uninflated state do not exceed a maximum predetermined value. The cross-sectional configuration of sidewalls are such that the thickness of the sidewall adjacent the bead area is at least 65% of the tire's sidewall thickness at the maximum tire section width. The thickness of each sidewall proceeding from the maximum section width to the shoulder area is equal to orgreaterthan the thickness of said sidewall atthe maximum tire section width.The portion of the sidewall radially and axially inward of the carcass ply structure is made of an elastomeric material having a dynamic modulus of not less than about 50 kg/cm2 and has a ratio of hysteresis to dynamic modulus not greater than about .24 /O/kg/cm2; the cross-sectional thickness of the sidewall portion radially and axially inward of the carcass ply structure at the maximum tire section width being at least 30% of the total sidewall cross-sectional thickness at the maximum tire section width exclusive of any innerlineror indicia. Stiffening members having a high dynamic modulus may be placed in the bead area of the tire.

Description ofthe drawings Figure 1 is a cross-sectional view of a tire made in accordance with the present invention mounted on a rim for which it is designed and inflated to design inflation pressures; Figure 2 in soiid lines illustrates a cross-sectional view of a tire made in accordance with the present invention mounted on a rim for which it is designed, in the uninflated state at rated load, and in dash lines there is illustrated a cross-sectional view of the tire as shown in Figure 1.

Figure 3 is a cross-sectional view of a modified tire made in accordance with the present invention; Figure 4 is a fragmentary side view of the tire of Figure 3 taken along line 4-4; and Figure 5 is an enlarged, fragmentary cross-sectional view of the tire of Figure 3 taken along line 5-5.

Detailed description ofpreferred embodiment Referring to Figure 1, there is illustrated a tire 10 made in accordance with the present invention. Tire 10 is provided with a ground-engaging tread portion 12. A pair of sidewall portions 14,16 extend from the shoulder portions 18,20 of the tread portion 12 and terminate in a pair of bead portions 22,24 having annular inextensible bead cores 26,28, respectively. The tire is further provided with a carcass ply structure 30 which extends from bead portion 22 to bead portion 24 and a tread-reinforcing belt structure 32 which extends circumferentially about the carcass ply structure 30 beneath the tread portion 12. The tire may include a conventional inner liner 13 forming the inner surface of the tire 10 if the tire is to be of the tubeless type.The ends 34,36 are of the carcass ply structure 30 and are wrapped about the bead cores 26,28, respectively, as shown in Figure 1.

The carcass ply structure 30 comprises at least one layer of rubber-coated fabric cords and is preferably of the radial type construction, that is, a carcass ply structure in which the cords form an angle from about 75 degrees to 90 degrees with respect to the mid-circumferential centerplane CP of the tire. However, the present invention may also be applied to bias ply tires, that is, tires in which the cords of the carcass ply structure form an angle less than about 75 degrees with respect to the mid-circumferential centerplane CP of the tire. Any number of carcass plies may be used, depending upon the size and load rating of the tire and may be of any suitable material used in tire reinforcement, for example, nylon, rayon, aramid, polyester, steel. In the particular embodiment illustrated, carcass ply structure 30 comprises two ply layers 42,44 having cords made of polyester.The carcass ply structure 30 is located approximately midway between the inner and outer surfaces of the tire in the region A of the sidewall which extends a point spaced from the nominal rim diameter NRD of about 35% of the carcass section height SH of the tire to a second point spaced a distance from the nominal rim diameter NRD of about 90% of the carcass section height SH of the tire.

The carcass aspect ratio may be any conventional ratio used in tire constructions which generally range from 50 to 95, preferably from 55 to 85, and in the particular embodiment illustrated, the carcass aspect ratio is approximately 75. For the purpose of this invention, the carcass aspect ratio denotes the relationship of the maximum carcass section heigh SH divided by the maximum carcass section width CSW as measured on an unloaded tire, inflated to design inflation pressures, mounted on a 70% rim. For the purpose of this invention, a 70% rim is a rim in which the axial distance R70 between the rim flanges is 70% of the maximum axial section width SD of the tire; the maximum axial section width SD being measured from the axially outer surfaces of the tire, exclusive of indicia, adornment and the like.The carcass aspect ratio is measured using the neutral carcass contour, which in a single radial ply carcass is the ply itself, but in a carcass ply structure having a plurality of plies, is located midway between the outermost and innermost plies. The maximum carcass section width CSW therefore is the maximum axial distance measured parallel to the axis of rotation between the neutral carcass contour of the carcass structure 30. The maximum carcass section height, therefore, is the maximum radial distance between the neutral contour of the carcass structure 30 beneath the tread portion 12 and the nominal rim diameter NRD as contained in the size designation of the tire.

Sidewall portions 14,16 have a cross-sectional configuration, as illustrated in Figure 1, such that the tire sidewall thickness at the area adjacent the bead areas is at least 65% of the cross-sectional thickness of the sidewall at Rho,. Preferably the sidewall thickness at this area is the thinnest area of the sidewall and proceeding radially outward to the point of maximum tire carcass section width Rhom the tire sidewall portions 14,16 gradually increase in cross-sectional thickness. For the purpose of this invention, the sidewall thickness at any point along the outside surface of the tire is the distance from that point to the closest point along the interior surface of the tire, exclusive of indicia, adornment or any other markings on the tire sidewall surface.

The tread width TW is at least 60% of the maximum axial carcass section width SD and is preferably not greater than 80%. In the particular embodiment illustrated, the tread width TW is approximately 70%. For the purpose of this invention, the tread with is the axial distance across the tire perpendicular to the mid-circumferential centerplane CP of the tire as measured from the footprint of the tire inflated to design inflation pressure, at rated load and mounted on a wheel for which it is designed.

In order to provide the support necessary in the uninflated state, the radially inner portions 46,48 of the sidewall portions 14,16, respectively, have a cross-sectional thickness of at least approximately 30% of the total sidewall thickness Tat the maximum tire section width Rhom exclusive of any indicia that may be present.

The radially outer ends 50,52 of the inner portions 46,48, respectively, terminate beneath the tread portion a distance B from the tread edge which it lies beneath; the distance B being not less than 35% of the distance C from the tread edge to the mid-circumferential centerplane CP, preferably not greater than 65%. In the particular embodiment illustrated, the ends 50,52 terminate beneath the tread a distance from the tread edge of approximately 45% of the distance C.

The belt reinforcing structure 32 comprises rubber coated fabric cords made of a material normally used in tires, for example, nylon, polyester, rayon, aramid, glass fiber, steel, and have one or more plies. In the particular embodiment illustrated, the reinforcing belt structure 32 comprises two reinforcing belt layers 47,49 each having its cords disposed at conventional angles with respect to the mid-circumferential plane CP of the tire which are normally used in conventional pneumatic tires, preferably from about 20 degrees to 25 degrees. In the particular embodiment illustrated the cords of reinforcing belt layers 47,49 form an angle of approximately 23 degrees with respect to the circumferential plane of the tire.Preferably, the cords of belt ply layer 47 lie at an angle with respect to the mid-circumferential plane of the tire which is opposite in sign than the angle in which the cords of layer 47 lie with respect to the mid-circumferential plane of the tire.

When the tire is operated in the uninflated condition, as is illustrated in Figure 2, the sidewall portions 14,16 support the vehicle load such that the internal surface of the tire does not contact any other part of the internal surface of the tire. The sidewalls 14,16 must be able to withstand the stresses encountered during operation of the tire in the uninflated condition. Failure of the tire when run in the uninflated state is primarily due to the chemical breakdown of the elastomeric material and the breakdown of the bond between the rubber of the elastomeric material and the reinforcements resulting from the excess heat build-up in the tire sidewall. It is desirable that the sidewall be made of a material that can support the vehicle load in the uninflated or underinflated condition with a minimum amount of heat build-up. Applicant has discovered that the sidewall thickness at the maximum section width SD of the carcass ply structure 30 should be such that the average maximum stress developed in the sidewall does not exceed approximately 8.7 x 105N/m2 in this area when operated in the uninflated state. In order to minimize the heat build-up in the sidewalls and provide the necessary support, the inner portions 46,48 are made of an elastomeric material having a ratio of hysteresis to dynamic modulus not greater than about .24%/kg/cm2, and a dynamic modulus of elasticity of not less than about 50 kg/cm2; preferably at least 85 kg/cm2.The dynamic modulus is obtained from the Goodyear Vibra Tester at about 60 cycles per second (ASTM D-2231) and the hysteresis is obtained from the Goodyear hot rebound test wherein hystersis is equal to 100% minus the percent rebound (ASTM D-1 054).

The stresses experienced in the sidewall of the tire are dependent upon the particular load to which the tire will be subjected in the uninflated condition and the configuration of the tire such as the bead spacing of the tire when mounted on a rim for which it is designed and the cross-sectional configuration of the tire sidewalls.The cross-sectional thickness of the tire sidewalls at the point of maximum carcass section width at Rho, of the tire 10 can be determined in accordance with the following relationship;

wherein: T is the total sidewall thickness at the point of maximum tire section width RhOrn exclusive of any indicia measured in millimeters; L is the load in kilograms at which the tire will be required to operate; RhOm is the radius from the axis of rotation of the tire to the point of maximum tire section width SD measured in millimeters; S70 is the maximum tire section width SD measured from the radially outer surface of the sidewall exclusive of adornment or other indicia, measured in millimeters when the tire is mounted on a 70% rim; and K is a constant which takes into account the maximum stresses that may be developed in the sidewall of the tire and is approximately equal to 8.9 x 10-1.

By taking into account the configuration of the tire sidewall and the load to which the tire will be subjected in the uninflated or partially uninflated state applicant has discovered a particular tire construction in which the tire's durability during operation in the uninflated condition is improved while at the same time maintaining the desired tire performance in the inflated normal operating condition.

A tire made in accordance with the present invention has been found to have acceptable commercial performance characteristics in the inflated condition while at the same time having satisfactory handling requirements in the uninflated condition. Atire made in accordance with the present invention having a ratio of hysteresis to dynamic modulus of about .16%/lcg/cm2 and a dynamic modulus of about 104 kg/cm2 has been found to be capable of being operated in the uninflated condition for a speed of up to 40 miles per hour for a distance of up to approximately 40 miles, which then can be repaired and returned to normal service.

In order to provide the stiffness in the bead area and a smooth transition between the stiff bead cores 26,28 and the respective sidewalls, stiffening members 38,40 are provided radially outwardly of the bead core 26,28 and between the carcass ply structure 32 and the ends 34,36 of the carcass ply structure. Stiffening members 38,40 are made of elastomeric material having a dynamic modulus of at least 125 kg/cm2 and preferably having a maximum ratio of hysteresis loss to dynamic modulus of about .17%/kg/cm2. The dynamic modulus and hysteresis values are determined by Goodyear Vibra Tester and Goodyear hot rebound test per ASTM D-2231 and ASTM D-1054, respectively.

The operating performance of tire 10 in the uninflated state may be enhanced by the placement of chafer portions 54,56 in the bead area adjacent the rim flange portions 60,62. When the tire is operated in the uninflated condition, a severe bending action occurs in the bead regions 22,24 about the rim flange portions 60, 62. Chafer portions 54,56 help counteract this bending action and minimize the flexing of the tire adjacent the rim flange portion 60,62. In the embodiment illustrated, the chafer portions 54,56 are made of an elastomeric material. However, chafer portions 54,56 may comprise a rubber-coated fabric. The chafer portions 54,56 are made of a material resistant to chafing and have a dynamic modulus at least equal to the dynamic modulus of the elastomeric material axially outward of the ply structure 30 and adjacent chafer portions 54,56.In the embodiment illustrated, the radially outermost points 64,66, of the chafer portions 54,56 respectively, extend radially outward beyond the flange contact point not less than about .5 of an inch (12.7 mm) as determined when the tire is mounted on a wheel for which it is designed to be used, and inflated to design inflation pressure. For the purpose of this invention, the flange contact point shall be the point at which the tire sidewall first contacts the rim proceeding from the tread portion to the bead portion.

The performance of the tire in the uninflated state may be further enhanced by providing the bead portions 22,24 with narrow reinforcing strips 58,59 axially outwardly of bead cores 26,28 extending circumferentially about the tire 10. In the embodiment illustrated reinforcing strip 58,59 are located axially outwardly of the ends 34,36 of the carcass ply structure 30, Reinforcing strips 58,59 enhance the bead area's resistance to compressive forces resulting from the tire bending aboutthe rim flange during operation in the uninflated or partially uninflated condition. The reinforcing strips 58,59 further provide an improved transition of stiffness from the stiff bead cores 26,28 to the softer sidewall compound.Reinforcing strips 58,59 comprise a plurality of parallel reinforcing cords, the cords being made from a highly compressive resistant material, for example, and not for the purpose of limitation, fiberglass or any metal. In the embodiment illustrated, the strips 58,59 comprise a plurality of reinforcing cords made from steel. To ensure continuity, the radially inner ends 68,70 should be located radially inward of the radially outermost point of the bead cores 26,28, respectively. Applicant has discovered that when the radially inner point of the reinforcing strips is above the radially outermost point of the bead core, stress concentrations may result and cause premature failure.The radially outer endings 72,74 of reinforcing strips 58,59 are preferably located radially outward from the rim flange contact point by at least about .2 of an inch (5.4 mm).

In order to assure that the bead portions 22,24 do not move from their respective rim bead seats 65,67 when the tire is operated in the uninflated state, some type of bead retention feature is preferably used. It has been found that the standard safety hump used on the JJ and JB rim, as specified by the Tire and Rim Association, provided the necessary support to retain the beads in their bead seat.

Prolonged use of the tire in the uninflated condition may be provided by providing a coolant in the tire cavity. The coolant may be present in the tire cavity during normal operating conditions or may be dispensed into the tire cavity when the tire goes into the underinflated or uninflated state. A tire made in accordance with the present invention having a ratio of hysteresis to dynamic modulus of about .16%/kg/cm2 and.a dynamic modulus of about 104 kg/cm2 and with the introduction of one pint of polyethyleneglycol into the tire cavity, has been found to be capable of traveling upward of 190 miles at 40 miles per hour which could then be inflated to normal operating pressures and returned to normal service.This is an increase of approximately 150 miles of additional travel of the tire as opposed to operating the tire without a coolant.

The amount of coolant necessary will, of course, be dependent upon the size of the tire and the physical properties of the particular coolant chosen.

Referring to Figures 3,4 and 5, there is illustrated a modified tire 110 made in accordance with the present invention. The radially inner surface 111 of the tire is shaped to have a plurality of substantially identically shaped corrugations 113 which extend in a substantially radial direction with respect to the midcircumferential plane of the tire and are spaced apart about the circumference of the tire 110. The cross-sectional configuration of the corrugations 113 may be sinusoidal as illustrated in Figure 4 or may take a variety of forms such as saw-toothed or stepped (not illustrated). Additionally, the configurations need not be equally spaced about the circumference of the tire.In the embodiment illustrated, the corrugations 111 113 have a substantially sinusoidal cross-sectional configuration, and are spaced substantially equidistant from each other about the circumference of the tire and extend substantially radially with respect to the mid-circumferential centerplane of the tire, starting from a point adjacent the bead area radially outward along the interior surface of the tire to a point beneath the tread portion terminating prior to reaching the mid-circumferential centerplane CP of the tire 110. Preferably the ends of the corrugations 113 beneath the tread portion terminate at a point spaced a distance from the tread edge equal to at least 35% of the distance C from the tread edge to the mid-circumferential plane of the tire.The tire 110, Figures 34 and 5 is similar to tire 10 of Figure 1, except that the sidewall thickness of the tire 110 takes into consideration the thickness of the corrugations 113. The sidewalls of the tire 110 follow the same relationship as the sidewalls 14,16 of the tire 10, except that the total sidewall thickness T of tire 110 is the sum of the mean corrugation height H and the interior sidewall thickness G. The interior sidewall thickness G being the distance from the base of the corrugation axially outward to the outer surface of the tire exclusive of any indicia that may be present. The mean corrugation height H as is shown in Figure 5, is the height from the base of the corrugation to the point wherein half of the cross-sectional area of the corrugation is above and half of the cross-sectional area of the corrugation is below.

While certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the artthatvarious changes and modifications may be made therein without departing from the spirit or scope of the invention.

Claims

1. A pneumatic safety tire comprising a circumferentially extending ground-engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground-engaging tread portion, a pair of bead portions, a pair of sidewall portions which extend from said shoulder portions to said bead portions, a carcass ply structure which extends from said bead portion to said bead portion, said tire characterized in that said sidewall portions have a predetermined thickness selected to provide that the average maximum stress developed in the elastomeric material does not exceed approximately 8.7 x 105 N/m2 when said tire is operated in the uninflated state, the inner sidewall portions radially inward with respect to the internal cavity of said tire of said carcass structure being made of an elastomeric material having a hysteresis to dynamic modulus ratio not greater than about .24 /O/kg/cm2 and a dynamic modulus of elasticity not less than about at least 50 kg/cm2.

2. A pneumatic safety tire comprising a circumferentially extending ground-engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground-engaging tread portion, a pair of bead portions, a pair of sidewall portions which extend from said shoulder portions to said bead portions, a carcass structure which extends from said bead portion to said bead portion, said tire characterized in that the mean thickness of said sidewall portions measured at the maximum tire section width of said tire corresponds to the following relationship::

wherein, T is the total sidewall thickness at the point of maximum tire section width Rho, exclusive of any indicia measured in millimeters; L is the load in kilograms at which the tire will be required to operate; Rho, is the radius from the axis of rotation of said tire to the point of maximum tire section width SD measured in millimeters; S70 is the maximum tire section width SD measured from the radially outer surfaces of the sidewall, exclusive of any adornment or indicia that may be present and measured parallel to the axis of rotation, measured in millimeters when said tire is mounted on a rim which has the axial flange surface spaced 70% of the maximum section width SD of the tire; and K is equal to approximately 8.9 x 10-1.

3. A pneumatic tire according to claim 1 wherein the inner sidewall portion radially inward with respect to the internal cavity of said tire of said carcass structure being made of an elastomeric material having a dynamic modulus of elasticity not less than about 85 kg/cm2.

4. A tire according to claim 1 or 2 wherein each of said sidewall portions have a cross-sectional configuration such that the mean thickness of said sidewall portion at the area adjacent said bead portions being at least 65% of the mean sidewall thickness at Rho,, the mean thickness of said sidewall portion proceeding from said point of maximum tire section width radially outward toward its respective shoulder portion being equal to or greater than the thickness of said sidewall portions at said maximum tire section width.

5. A tire according to claim 2 wherein the radially inner portion of each of said sidewall portions radially inward of said carcass ply structure having a cross-sectional mean thickness at the maximum tire section width of said tire of at least 30% of the total thickness of said sidewall portion at said point exclusive of said carcass ply structure or inner liner that may be present.

6. Atire according to claim 1 or 2 wherein the radially outer ends of said inner portion of each of said sidewall portions terminate at a point spaced a distance from the tread edge which it lies beneath of at least 35% of the distance from the tread edge to the mid-circumferential centerplane of said tire.

7. A tire according to claim 1 or 2 wherein said bead portions are each reinforced with a stiffening member located radially outward of each of said bead cores and between said carcass ply structure and the ends of said carcass ply structure, said stiffening members having a dynamic modulus of 125 kg/cm2 and a maximum ratio of hysteresis loss to dynamic modulus of .15 /O/kg/cm2.

8. A tire according to claim 1 or 2 wherein said bead portions are each provided with a chafer portion adjacent the rim flange contact area, said chafer portion having a dynamic modulus of at least 125 kg/cm2.

9. A tire according to claim 1 or 2 wherein each of said bead portions of said tire being further provided with a narrow reinforcing strip located axially outward of said respective bead core and said end of said carcass ply structure extending circumferentially about the tire.

10. A tire according to claim 1 or 2 wherein said tire is provided with a coolant in the tire cavity when operated in the underinflated or uninflated state.

11. A pneumatic safety tire comprising a circumferentially extending ground-engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground-engaging tread portion, a pair of bead portions, a pair of sidewall portions which extend from said shoulder portions to said bead portions, a carcass ply structure which extends from said bead portion to said bead portion, said tire characterized in said sidewall portions have a predetermined thickness selected to provide that the maximum stress developed in said elastomeric material does not exceed approximately 8.7 x 105 N/m2 when said tire is operated in the uninflated state, the inner sidewall portions radially inward of said carcass ply structure with respect to the internal cavity of said tire being made of an elastomeric material having a hysteresis to dynamic modulus ratio not greaterthan about .24%/kg/cm2 and a dynamic modulus of elasticity not less than about 50 kg/cm2 and having a cross-sectional thickness at the maximum tire section width of at least 30% of the total thickness of said sidewall portion at said point exclusive of said carcass ply structure or any inner liner that may be present.

12. A pneumatic safety tire comprising a circumferentially extending ground-engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground-engaging tread portion, a pair of bead portions, a pair of sidewall portions which extend from said shoulder portions to said bead portions a carcass structure which extends from said bead portion to said bead portion, said tire characterized in that said sidewall mean thickness as measured at the maximum tire section width of the tire corresponds to the following relationship:

wherein:: T is the total sidewall thickness at the point of maximum tire section width Rhom exclusive of any indicia measured in millimeters; Lithe load in kilograms at which the tire will be required to operate; Rho, is the radius from the axis of rotation of said tire to the point of maximum tire section width measured in millimeters; S70 is the maximum tire section width SD measured from the radially outer surfaces of the sidewall, exclusive of any adornment or indicia that may be present and measured parallel to the axis of rotation, measured in millimeters when said tire is mounted on a rim which has the axial flange surface spaced 70% of the maximum section width SD of the tire; and K is equal to approximately 8.9 x 10-1, the inner sidewall portions radially inward of said carcass ply structure with respect to the internal cavity of said tire being made of an elastomeric material having a hysteresis to dynamic modulus ratio not greater than about .24%/kg/cm2 and a dynamic modulus of elasticity not less than about 50 kg/cm2 and having a cross-sectional thickness at the maximum tire section width of at least 30% of the total thickness of said sidewall portion at said point exclusive of said carcass ply structure or any innerliner that may be present.

13. A pneumatic tire according to claim 11 dr 12 wherein the inner sidewall portion radially inward with respect to the internal cavity of said tire of said carcass structure being made of an elastomeric material having a dynamic modulus of elasticity not less than about 85 kg/cm2.

14. A tire according to claim 11 or 12 wherein said bead regions are each reinforced with a stiffening member located radially outward of the bead cores and between the carcass structure and the respective end of said carcass structure, said stiffening member having a dynamic modulus of 125 kg/cm2 and a maximum ratio of hysteresis loss to dynamic stiffness of .1 7%/kg/cm2.

15. A tire according to claim 11 or 12 wherein each of said sidewall portions have a cross-sectional configuration such that the mean thickness of said sidewall portion at the area adjacent said bead portions being at least 65% of the mean radial thickness at Room, the mean thickness of said sidewall portion proceeding from said point of maximum tire section width radially outward toward is respective shoulder portion being equal to or greater than the thickness of said sidewall portions at said maximum tire section width, said bead portions are each reinforced with a stiffening member located radially outward of each of said bead cores andbetween the carcass structure and the ends of said carcass structure, said stiffening members having a dynamic modulus of about 125 kg/cm2 and a maximum ratio of hysteresis loss to dynamic stiffness of about .17%/kg/cm2.

16. A tire according to claim 11 or 12 wherein each of said sidewall portions have a cross-sectional configuration such that the mean thickness of said sidewall portion at the area adjacent said bead portions being at least 65% of the mean sidewall thickness at Rko,, the mean thickness of said sidewall portion proceeding from said point of maximum tire section width radially outward toward its respective shoulder portion being equal to or greater than the thickness of said sidewall portions at said maximum tire section width, the radially outer ends of said inner portions of each of said sidewall portions terminate a distance from the tread edge which it lies beneath a distance not less than about 35% of the distance from the tread edge to the mid-circumferential centerplane of said tire, said bead portions are each reinforced with a stiffening member located radially outward of each of said bead cores and between the carcass structure and the ends of said carcass structure, said stiffening members having a dynamic modulus of about 125 kg/cm2 and a maximum ratio of hysteresis loss to dynamic stiffness of about .1 .17%/kg/cm2.

17. Atire according to claim 11 or 12 wherein each of said sidewall portions have a cross-sectional configuration such that the mean thickness of said sidewall portion at the area adjacent said bead portions, being at least 65% of the mean sidewall thickness at Rho,, the mean thickness of said sidewall portion proceeding from said point of maximum tire section width radially outward toward its respective shoulder portion being equal to or greater than the thickness of said sidewall portions at said maximum tire section width, said bead portions are each reinforced with a stiffening member located radially outward of each of said bead cores and between the carcass structure and the ends of said carcass structure, said stiffening members having a dynamic modulus of about 125 kg/cm2 and a maximum ratio of hysteresis loss to dynamic stiffness of about .17 /O/kg/cm2 each of said bead portions being further provided with a narrow reinforcing strip located axially outward of said respective bead cores and said end of said carcass structure extending circumferentially about the tire.

18. A pneumatic safety tire cornprising a circumferentially extending ground-engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground-engaging tread portion, a pair of bead portions, a pair of sidewall portions which extend from said shoulder portions to said bead portions, a carcass structure which extends from said bead portion to said bead portion, said tire characterized in that said sidewall portions have a predetermined thickness selected to provide that the average maximum stress developed in the elastomeric material does not exceed approximately 8.7 :; x 105 N/m2 when said tire is operated in the uninflated state, the inner sidewall portions radially inward with respect to the internal cavity of said tire of said carcass structure being made of an elastomeric material having a hysteresis to dynamic modulus ratio not greater than about .24%/kg/cm2, and a dynamic modulus of elasticity not less than about 50 kg/cm2 and having cross-sectional thickness at the maximum tire section width of at least 30% of the total thickness of said point exclusive of said carcass ply structure or inner liner that may be present, each of said sidewall portions have a cross-sectional configuration such that the mean thickness of said sidewall portion at the area adjacent said bead portions being at least 65% of the mean thickness at Rho,, the mean thickness of said sidewall portion proceeding from said point of maximum tire section width radially outward toward its respective shoulder portion being equal to or greater than the thickness of said sidewall portions at said maximum tire section width.

19. A pneumatic safety tire comprising a circumferentially extending ground-engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground-engaging tread portion, a pair of bead portio portions, a pair of sidewall portions which extend from said shoulder portions to said bead portions, a carcass structure which extends from said bead portion to said bead portion, said tire characterized in that said sidewall mean thickness as measured at the maximum tire section width of the tire corresponds to the following relationship:

wherein:: T is the total sidewall thickness at the point of maximum tire section width Rho, exlusive of any indicia measured in millimeters; L is the load in kilograms at which the tire will be required to operate; Rho, is the radius from the axis of rotation of said tire to the point of maximum tire section width measured in millimeters; S70 is the maximum tire section width SD measured from the radially outer surfaces of the sidewall, exclusive of any adornment or indicia that may be present and measured parallel to the axis of rotation, measured in millimeters when said tire is mounted on a rim which has the axial flange surface spaced 70% of the maximum section width SD of the tire; and K is equal to approximately 8.9 x 10-'. each of side sidewall portions have a cross-sectional configuration such that the mean thickness of said sidewall portion at the area adjacent said bead portions being at least 65% of the sidewall thickness at Room, the mean thickness of said sidewall portion proceeding from said point of maximum tire section width radially outward toward its respective shoulder portion being equal to or greater than the thickness of said sidewall portions at said maximum tire section width, the radially inner portion of each of said sidewall portions radially inward of said carcass structure being made of an elastomeric material having hysteresis to dynamic modulus ratio not greater than about .24%1kgicm2, a modulus not less than about 50 kg/cm2 and having cross-sectional thickness at the maximum tire section width of at least 30% of the total thickness of said sidewall portion at said point exclusive of said carcass ply structure or inner liner that may be present.

20. A tire according to claim 16 or 17 wherein the radially outer ends of said inner portions of each of said sidewall portions terminate a distance from the tread edge which it lies beneath a distance not less than about 35 percent of the distance from the tread edge to the mid-circumferential centerplane of said tire, said bead portions are each reinforced witha stiffening members located radially outward of each of said bead cores and between the carcass structure and the ends of said carcass structure, said stiffening members having a dynamic modulus of about 125 kg/cm2 and a maximum ratio of hysteresis loss to dynamic stiffness of about .17%/kg/cm2.

21. A tire according to claim 16 or 17 wherein the radially outer ends of said inner portions of each of said sidewall portions terminate a distance from the tread edge which it lies beneath a distance equal to at least 35 percent of the distance from the tread edge to the mid-circumferential centerplane of said tire, said bead regions are each reinforced with stiffening members located radially outward of the bead cores and between the carcass structure and the ends of said carcass structure, said stiffening members having a dynamic modulus of 125 kg/cm2 and a maximum ratio of hysteresis loss to dynamic stiffness of .17%/kg/cm2, said bead portions being further provided with chafer portions adjacent the rim flange contact area, said chafer portions having a dynamic modulus of at least 125 kg/cm2.

22. A pneumatic safety tire comprising a circumferentially extending ground-engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground-engaging tread portion, a pair of bead portions, a pair of sidewall portions which extend from said shoulder portions to said bead portions, a carcass structure which extends from said bead portion to said bead portion, said tire characterized in that said sidewall portions have a predetermined thickness selected to provide that the average maximum stress developed in the elastomeric material does not exceed approximately 8.7 x 105 N/m2 when said tire is operated in the uninflated state, the inner sidewall portions radially inward with respect to the internal cavity of said tire of said carcass structure being made of an elastomeric material having a hysteresis to dynamic modulus ratio not greater than about .24kg/cm2 and a dynamic modulus of elasticity not less than about 50 kg/cm2, each of said sidewall portions have a cross-sectional configuration such that the mean thickness of said sidewall portion at the area adjacent said bead portions being at least 65% of the mean sidewall thickness Room, the mean thickness of said sidewall portions proceeding from said area adjacent said bead portions radially outward to the point of maximum tire section width continuously increase in cross-sectional thickness, the mean thickness of said sidewall portion proceeding from said point of maximum tire section width radially outward toward its respective shoulder portion being equal to or greater than the thickness of said sidewall portions at said maximum tire section width, the radially outer ends of said inner portions of each of said sidewall portions being no less than 65 percent of the mean thickness of said sidewall portions at said maximum tire section width, the radially outer ends of said inner portions of each of said sidewall portions terminate a distance from the tread edge which it lies beneath a distance equal to at least 35 percent of the distance from the tread edge to the mid-circumferential centerplane of said tire, said bead portions are each reinforced with a stiffening member located radially outward of each of said bead cores and between the carcass structure and the ends of said carcass structure, said stiffening members having a dynamic modulus of about 125 kg/cm2 and a maximum ratio of hysteresis loss to dynamic stiffness of about .17%/kg/cm2.

23. A pneumatic safety tire comprising a circumferentially extending ground engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground engaging tread portion, a pair of bead portions, a pair of sidewall portions which extend from said shoulder portions to said bead portions, a carcass structure which extends from said bead portion to said bead portion, said tire characterized in that the mean thickness of said sidewall portions measured at the maximum tire section width of said tire corresponds to the following relationship:

wherein: : T is the total sidewall thickness at the point of maximum tire section width Rho, exclusive of any indicia measured in millimeters; L is the load in kilograms at which the tire will be required to operate; Rhom is the radius from the axis of rotation of said tire to the point of maximum tire section width measured in millimeters; S70 is the maximum tire section width SD measured from the radially outer surfaces of the sidewall, exclusive of any adornment or indicia that may be present and measured parallel to the axis of rotation, measured in millimeters when said tire is mounted on a rim which has the axial flange surface spaced 70% of the maximum section width SD of the tire; and K is equal to approximately 8.9 x 10-1.

each of said sidewall portions have a cross-sectional configuration such that the mean thickness of said sidewall portion at the area adjacent said bead portions being at least 65% of the mean sidewall thickness at Rho,, the mean thickness of said sidewall portions proceeding from said area adjacent said bead portions radially outward to the point of maximum tire section width continuously increase in cross-sectional thickness, the mean thickness of said sidewall portion proceeding from said point of maximum tire section width radially outward toward its respective shoulder portion being equal to or greater than the thickness of said sidewall portions at said maximum tire section width, the radially inner portion of each of said sidewall portions radially inward of said carcass structure being made of an elastomeric material having hysteresis to dynamic modulus ratio not greater than about .24%/kg/cm2, a modulus not less than 50 kg/cm2 and having cross-sectional thickness at the maximum tire section width of at least 30% of the total thickness of said sidewall portion at said point exclusive of said carcass ply structure or inner liner that may be present, said bead portions are each reinforced with stiffening members located radially outward of each of said bead cores and between the carcass structure and the ends of said carcass structure, said stiffening members having a dynamic modulus of about .17%/kg/cm2.

24. A tire according to claim 20 or 21 wherein each of said bead portions being further provided with a chafer portion adjacent the rim flange contact area, said chafer portions having a dynamic modulus of at least 125 kg/cm2.

25. Atire according to claim 20 or 21 wherein each of said bead portions being further provided with narrow reinforcing strip located axially outward of said respective bead cores.

26. A tire according to claim 20 or 21 wherein each of said bead portions being provided with a chafer portion adjacent the rim flange contact area, said chafer portions having a dynamic modulus of at least 125 kg/cm2, each of said bead portions being further provided with a narrow reinforcing strip located axially outward of said respective bead cores.

27. A tire and rim assembly, said tire comprising a circumferentially extending ground-engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground-engaging tread portion, a pair of bead portions, a pair of sidewall portions which extend from said shoulder portions to said bead portions, a carcass ply structure which extends from said bead portion to said bead portion, said tire characterized in that said sidewall portions have a predetermined thickness selected to provide that the average maximum stress developed in the elastomeric material does not exceed approximately 8.7 x 105 N/m2 when said tire is operated in the uninflated state, the inner sidewall portions radially inward with respect to the internal cavity of said tire of said carcass structure being made of an elastomeric material having a hysteresis to dynamic modulus ratio not greater than about .24%/kg/cm2 and a dynamic modulus of elasticity not less than about at least 50 kg/cm2, said rim having a pair of bead seats for seating of said bead portions, a circumferentially extending safety hump on each of said bead seats for maintaining said bead portions in said bead seats when said tire is operated in the uninflated condition.

28. A tire and rim assembly, said tire comprising a circumferentially extending ground-engaging tread portion, a pair of shoulder portions adjacent the axially outer end of said ground engaging tread portion, a pair of bead portions, a pair of sidewall portion which extend from said shoulder portions to said bead portions, a carcass structure which extends from said bead portion to said bead portion, said tire characterized in that the mean thickness of said sidewall portions measured at the maximum tire section width of said tire corresponds to the following relationship:

wherein:: T is the total sidewall thickness at the point of maximum tire section width Rho, exclusive of any indicia measured in millimeters; L is the load in kilograms at which the tire will be required to operate; Rho, is the radius from the axis of rotation of said tire to the point of maximum tire section width measured in millimeters; S70 is the maximum tire section width SD measured from the radially outer surfaces of the sidewall, exclusive of any adornment or indicia that may be present and measured parallel to the axis of rotation, measured in millimeters when said tire is mounted on a rim which has the axial flange surface spaced 70% of the maximum section width SD of the tire; and Kis equal to approximately 8.9 x 10-1.

29. A pneumatic safety tire and rim assembly according to claim 27 and 28 wherein said bead portions are each provided with a chafer portion adjacent the rim flange contact area, said chafer portion having a dynamic modulus of at least 125 kg/cm2, the radially outer end of said chafer portion extends radially outwardly from the rim flange contact point by at least about .2 of an inch (5.4 mm).