WO1998056605A1

WO1998056605A1 - Aircraft tire with embedded breaker plies

Info

Publication number: WO1998056605A1
Application number: PCT/US1997/010426
Authority: WO
Inventors: Glenn Richard Moore; Mohammad E. Sobhanie; Michael W. Cook
Original assignee: The Goodyear Tire & Rubber Company
Priority date: 1997-06-13
Filing date: 1997-06-13
Publication date: 1998-12-17
Also published as: AU4581797A

Abstract

A double-loaded rated pneumatic tire for an aircraft is constructed with a multi-layered carcass having breaker plies embedded therein and of different lengths to support the tread portion.

Description

AIRCRAFT TIRE WITH EMBEDDED BREAKER PLIES

TECHNICAL FIELD

The present invention relates to pneumatic tires and more particularly to a novel carcass specifically for use in aircraft tires.

BACKGROUND OF THE INVENTION

An aircraft tire is subjected to extreme operating conditions which include very high internal pressure, high speeds in excess of 300 kilometers per hour (kph), and very high deflections of the section height between the wheel flange and the outside diameter of the tire. While taxiing, the deflection may be more than 30%, on takeoff 40%, and on landing 45% or more under impact conditions. These extreme pressures, loads and deflections put the sidewall between the shoulder of the tire and the bead to severe tests. The high pressure and high loads place the ply cords under severe tensile loads. The cords in the plies, particularly in the lower sidewall area, are frequently mechanically fatigued due to a high heat buildup near the beads while the aircraft is taxiing or during takeoff. In the prior art, the conventional solution to these problems was to increase the tire rigidity and to decrease tire deformation under load by increasing the number of tire plies. To further improve tire durability, the ply turnup portion of tires was typically reinforced. U.S. Patent No. 5,105,865 by Togashi et al . describes these conventional solutions and proposes that the durability of the tire can be further improved by avoiding bending deformations of

the ply surfaces. The 5,105,865 patent describes a tire

curvature that increases the tire durability with no increase in

weight .

U.S. Patent No. 4,029,137 by Suydam teaches that an

improvement in durability can be achieved with a novel wrapping

of the ply structure about the beads. The 4,029,137 patent also

discloses a means of improving tire durability without

increasing weight .

In British Patent GB 2,087,806 by Takahaski, a biased

aircraft tire is disclosed wherein the cords of the carcass

plies are spaced further apart to achieve improved durability.

U.S. Patent No. 5,509,455 by Warchol et al . discloses an

aircraft tire with circumferentially extending reinforcement

inserts on each side of the tire. Each of the inserts has cord

reinforced members with bias angled cords that are equal but

opposite in orientation relative to the cords of the adjacent

member. The structure increases ply durability while achieving

a significant weight reduction. With increasing aircraft performance, it is apparent that

there is a continuing need to provide novel methods and tire

designs for improving aircraft tire durability.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a pneumatic tire for an aircraft, the pneumatic tire being as defined in one or more of the appended claims and, as such,

having the capability of being constructed to accomplish one or

more of the following subsidiary objects.

It is another object of the present invention to provide a

pneumatic tire for an aircraft which meets the requirements for

double load capability required for aircraft tires.

It is a further object of the present invention to provide

a pneumatic tire for an aircraft wherein breaker plies are

embedded within a multi-layered carcass so that the ends of the

breaker plies are disposed at a location near the sidewalls of

the tire where the tread thickness is at least about 40% of the

maximum thickness of the tread.

It is a yet further object of the present invention to

provide a pneumatic tire for an aircraft wherein tread plies are

located between the multi-layered carcass and the tread

portion and extend across the carcass toward the sidewalls so

that the ends of the tread plies are disposed at a location near

the sidewalls where the tread thickness is between about 60% and

85% of the maximum tire tread thickness.

It is a yet further object of the present invention to

provide a pneumatic tire for an aircraft that improves sidewall

durability while achieving a reduction in overall tire weight. In accordance with an embodiment of the invention, a

pneumatic tire for an aircraft is disclosed which is constructed

of a multi-layered carcass composed of a plurality of ply layers

and a pair of spaced apart bead portions having at least two

substantially inextensible bead cores disposed side by side and

spaced apart axially. The ply layers have carcass plies

extending circumferentially about the tire and between the bead

cores of opposite bead portions. A tread portion overlies the

multi-layered carcass and a pair of sidewall portions extend

from the bead portions to the tread portion. At least two

breaker plies are embedded within the multi- layered carcass

above the carcass plies. The breaker plies extend entirely

about the circumference of the tire and below the tread portion.

The first and second breaker plies are buried in the carcass so

that their first and second opposite ends are disposed at a

location where the tread portion has a thickness above about 60%

to about 85% of the maximum thickness of the tread portion

measured at the equatorial plane through the tire. The first

breaker ply is above the second breaker ply and has opposite

ends that are disposed at a location where the tread portion has

a thickness of about 20% to about 45% more than the thickness of

the tread portion at the location of the opposite ends of the

second breaker ply. Also, the second breaker ply is longer than

the first breaker ply so that the ends of the second breaker ply are disposed closer to the pair of spaced apart bead portions

than the ends of the first breaker ply.

Also according to the invention, the tire includes tread

plies disposed in the tread portion so that the ends of the

tread plies are positioned with respect to the tread at a

location corresponding to between about 60% and 85% of the

maximum tire section thickness. Also, the tread plies are

shorter than either of the breaker plies.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross-sectional view illustrating the improved

aircraft tire made in accordance with the present invention;

Fig. 2 is a further enlarged cross-sectional view

illustrating one side or half of the symmetrical tire shown in

Fig. 1 and made in accordance with the present invention; and

Fig. 3 is an alternative embodiment showing two pairs of

breaker plies embedded within the carcass.

DEFINITIONS

"Apex" means a non-reinforced elastomer positioned radially

above a bead core .

"Aspect ratio" of the tire means the ratio of its section

height (SH) to its section width (SW) multiplied by 100% for

expression as a percentage.

"Axial" and "axially" means lines or directions that are

parallel to the axis of rotation of the tire. "Bead" means that part of the tire comprising an annular

tensile member wrapped by the ply cords and shaped, with or

without other reinforcement elements such as flippers, chippers,

apexes, toe guards and chafers, to fit the design rim.

"Belt or breaker reinforcing structure" means at least two

layers of plies of parallel cords, woven or unwoven, underlying

the tread, unanchored to the bead, and having both left and

right cord angles in the range from 17 degrees to 40 degrees

with respect to the equatorial plane of the tire.

"Bias ply tire" means a tire having a carcass with

reinforcing cords in the carcass ply extending diagonally across

the tire from bead core to bead core at about 25°-50° angle with

respect to the equatorial plane of the tire. Cords run at

opposite angles in alternate layers.

"Carcass" means the tire structure apart from the belt

structure, tread, undertread, and sidewall rubber over the

plies, but including the beads.

"Circumferential" means lines or directions extending along

the perimeter of the surface of the annular tread perpendicular

to the axial direction.

"Chafers" refers to narrow strips of material placed around

the outside of the bead to protect cord plies from the rim,

distribute flexing above the rim, and to seal the tire. "Chippers" means a reinforcement structure located in the

bead portion of the tire.

"Cord" means one of the reinforcement strands of which the

plies in the tire are comprised.

"Equatorial plane (EP) " means the plane perpendicular to

the tire's axis of rotation and passing through the center of

its tread.

"Flipper" means a reinforced fabric wrapped about the bead

core and apex.

"Footprint" means the contact patch or area of contact of

the tire tread with a flat surface at zero speed and under

normal load and pressure.

"Inner liner" means the layer or layers of elastomer or

other material that form the inside surface of a tubeless tire

and that contain the inflating gas or fluid within the tire.

"Net-to-gross ratio" means the ratio of the tire tread

rubber that makes contact with the road surface while in the

footprint, divided by the area of the tread in the footprint,

including non-contacting portions such as grooves.

"Nominal rim diameter" means the average diameter of the

rim flange at the location where the bead portion of the tire

seals .

"Normal inflation pressure" refers to the specific design

inflation pressure at a specific load assigned by the appropriate standards organization for the service condition for

the tire.

"Normal load" refers to the specific load at a specific

design inflation pressure assigned by the appropriate standards

organization for the service condition for the tire.

"Ply" means a continuous layer of rubber-coated parallel cords .

"Radial and "radially" means directions extending radially

toward or away from the axis of rotation of the tire.

"Radial-ply tire" means a belted or circumferentially-

restricted pneumatic tire in which the ply cords which extend

from bead to bead are laid at cord angles between 65° and 90°

with respect to the equatorial plane of the tire.

"Section height (SH)" means the radial distance from the

nominal rim diameter to the outer diameter of the tire at its

equatorial plane.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Fig. 1, there is illustrated a cross-

section of tire 10 which in the specific embodiment illustrated

is a size H43.5X16.0-21 tire. The tire has a 43.5 inch (110.5

cm) maximum inflated outside diameter, a 16.0 inch (40.6 cm)

maximum inflated width tire in the axial directions, and a

nominal bead diameter of 21 inches (53.3 cm) . While a specific tire size is illustrated, it is within the terms of the

invention to incorporate the present invention in any tire

between H31X13.0-12 up through H54X21.0-24.

The tire 10 includes a ground engaging, circumferentially

extending tire tread portion 12, a pair of tire sidewalls 14,16

extending radially inwardly from the axially disposed outer

edges of the tread portion and terminating at their radial

extremities in a pair of bead portions 18,20, respectively. The

sidewalls 14,16 each have an upper portion 14a, 16a,

respectively, in the shoulder region of the tire radially

outward of the tread and radially inward of the maximum section

width of the tire, and a lower portion 14b, 16b, respectively,

adjacent the bead portions 18, 20 and radially inward of the

maximum section width of the tire 10. The tire 10 also includes

a cord reinforced carcass structure 22 that extends

circumferentially about the tire and from bead portion 18 to

bead portion 20. The cord reinforced carcass structure 22 is

constructed of a plurality of rubberized laminated ply layers of

tire cord fabric.

The cord reinforcing carcass structure 22 includes twelve

biased carcass plies of tire cord fabric 24, 25, 26, 27, 28, 29,

30, 31, 32, 33, 34, 35 (24-35). Each of the biased carcass

plies extends at a bias angle with respect to the equatorial

plane or circumferential center line of the tire, and the adjacent biased carcass plies are disposed at the same angle but

extending in the opposite direction with respect to the

equatorial plane . The angle that the cords in the individual

carcass plies make with respect to the equatorial plane

decreases progressively from an angle of about 31° in the biased

inner ply 24 to about 28.5° in the biased outer ply 35. While

the illustrated embodiment incorporates twelve biased carcass

plies, it is within the terms of the invention to use more or

less plies depending upon the specific requirements for the

tire.

Also included in the tire tread portion 12 is a pair of

tread belts plies 40 and 42 extending circumferentially about

tire 10 and located between tread 43 and a conventional buff

line cushion gum layer 44 that generally extends from one edge

of the tread portion 12 to the axially opposite edge of the

tread portion 12. The tread plies 40, 42 reinforce and

strengthen the tread 43. The tread plies 40 and 42 have a

maximum width where their ends 40a, 40b, 42a, and 42b are

positioned with respect to the tread 43 at a location

corresponding to between about 60% and 85% and preferably about

65% to about 80% and most preferably about 65% of the maximum

tire section thickness "t" measured at the equatorial plane 60

passing through the center of tread 43. The angle of the cords

in the tread plies 40 and 42 with respect to the equatorial plane 60 is between about 20° and 30° and preferably about 26°.

Preferably, the width of tread ply 42, is less than the width of

tread ply 40 so that ends 40a, 40b of- tread ply 40 are located

closer to sidewalls 14 and 16, respectively, as compared to ends

42a, 42b of tread ply 42. While two tread plies 40 and 42 are

illustrated, it is also within the terms of the invention to use

between one and four tread plies as required.

The material of the cords in all of the plies forming the

carcass structure 22 is nylon although any suitable material or

combination of materials can be utilized. It is believed

preferable that the cords be a textile material. Further, while

specific angles have been specified for the carcass and tread

plies, these angles can be varied within the normal range of

bias ply aircraft tires. For example, the angles of the carcass

plies can be from between about 25° to 45° for a biased ply

aircraft tire.

The bead portions 18, 20 each include three annular,

substantially inextensible bead cores 50, 52 and 54. Two

carcass plies 24 and 25 are disposed radially inwardly of the

tire 10 adjacent to the axially disposed inner sides of the

axially located inner bead core 50. The respective end portions

24a and 25a are turned axially outwardly across bead cores 52

and 54 and then turned radially outward about bead core 54.

Carcass plies 26, 27, 28 and 29 are disposed axially outward from carcass plies 24 and 25 and radially adjacent to the inner

sides of bead core 50. Further, end portions 26a, 27a, 28a,

29a, of carcass plies 26, 27, 28 and 29, respectively, are

turned radially outwardly and then about bead core 50. Since

the carcass plies 26, 27, 28, 29 are wrapped around two sides of

bead core 50, as the progress radially outward toward sidewall

14, the tensile loading of these plies caused by inflation

pressure and loading on the tire are supported by bead core 50.

The carcass plies 30 and 31 are disposed radially inwardly

of the tire 10 adjacent to the bead core 52 and axially outward

from carcass plies 26-29. The plies 30 and 31 extend between

the bead cores 50 and 52 with their respective end portions 30a

and 30b being wrapped axially outward and about bead core 52 as

they progress radially outward toward the sidewall 14. Since

the carcass plies 30a and 31a are wrapped about two sides of the

bead core 52 as they progress radially outward, the tensile

loading of these plies caused by inflation pressure and loading

on the tire are supported by bead core 52.

The axially disposed, outer bead core 54 has two carcass

plies 32 and 33 extending radially inwardly adjacent the axially

inner sides of the bead core 54. Carcass plies 32 and 33 have

their end portions 32a and 33a, respectively, turned axially

outward adjacent the radially outward sides of the bead core 54. The bead core 54 supports the tensile loading applied to the

plies 32, 33, by inflation pressure and loading on the tire 10.

The outer most carcass plies 34 and 35 extend radially

inward from sidewalls 14 and 16, respectively, and are

interposed between the turnup ends 24a and 25a of plies 24 and

25, respectively, and the axially outer sides of the bead core

54. The carcass ply end portions 34a and 35a turn axially

inward adjacent the bead core 54 and then extend inwardly to the

bead core 50. The end portions 34a and 35a being interposed

between the bead cores 50, 52 and 54 and the radially inner

sides of carcass plies 24 and 25, cause the bead cores 50, 52

and 54 to support the tensile loading applied to the plies 34

and 35 by inflation pressure and loading on the tire.

The carcass plies 24 and 25 extend radially outward of tire

10 and are interposed between the tread portion 12, the

sidewalls 14 and 16 and the inner liner 80. The end portions

24a and 25a terminate in the lower sidewall areas 14a, 14b,

respectively, at a point radially outwardly of the bead cores

50, 52, and 54 to support the tensile loading applied to the

plies 24 and 25.

For the purposes of this invention, an end portion shall be

that portion of a carcass ply that wraps about or extends

radially outward from a bead core. If an end portion terminates

short of the point of maximum axial width of the tire, it is not considered a working portion of the ply since it does not exert

a significant radially outward directed pull on the bead core.

A bead core that absorbs a major radially outwardly directed

pull of a carcass ply is an active or working bead core, and for

purposes of this invention is a bead core bounded on any axial

side and a radially inner side by the working portion of a

carcass ply. The working portion of a carcass ply is that

portion of the ply extending from a bead on one side of the tire

to the opposite side's bead, and for purposes of this invention

the working portion of the carcass plies is called the ply side;

the non-working portion is the turn-up or end portion of the

ply.

Referring to Fig. 2 there is an enlarged illustration of a

group of structural components employed in the tire 10.

Radially above each bead core 50, 52, 54 is an elastomeric apex

62, 64, 66, respectively. Wrapped about each bead core 50, 52,

54 and corresponding axially adjacent apex 62, 64, 66,

respectively, is a flipper 68, 70, 72, respectively. Wrapped

about the entire bead structure is a chafer 74. The chafer 74

extends radially inwardly from an axially outer end 74a toward

the bead heel 76, turns axially inwardly extending to the bead

toe 78 where the chafer 74 turn radially outwardly to an inner

end 74b. In the embodiment as illustrated, the air chamber formed by the tire is surrounded by a generally air impervious

innerliner 80 extending from bead portion 18 to bead portion 20.

Historically, bias ply aircraft tires have been designed

with full width carcass plies, which extend from a bead bundle

or portion on one side of the tire to the bead bundle or portion

on the other side of the tire. The breaker plies were typically

between the buff line cushion layer and the tread portion and in

spaced relationship from the carcass. In order to increase

carcass strength in any one area of the tire, it was common

practice to add full width plies to the carcass.

In accordance with the present invention, first and second

breaker plies 46 and 48 are buried in carcass structure 22 and

extend beyond the ends of the tread plies 40 and 42. While the

breaker plies 46 and 48 are illustrated as being disposed in

carcass 22 between the plies 33 and 34, it is within the terms

of the invention to locate the breaker plies at other locations

within the carcass. Further, while two breaker plies are

illustrated, it is within the terms of the invention to use two

pairs of breaker plies. The two pairs could either be disposed

adjacent one another or separated by one or more carcass plies.

The ends 46a, 46b and 48a, 48b of the breaker plies 46 and 48,

respectively, extend outward from the equatorial plane 60 to a

location where the thickness t_a, t_b of the tire tread portion 12

is equal to between about 60% and about 85% of the maximum tire section thickness "t" when the tire is mounted and inflated to

its normal inflation pressure. The location of the ends of the

buried breaker plies 46 and 48 is an important aspect of the

invention. The ends 46a, 46b, 48a, 48b of breaker plies 46 and

48, respectively, extend outward towards the upper portions 14a

and 16a of sidewalls 14 and 16, respectively. The length of the

breaker plies is limited in that if they were to extend to a

location where t_a or t_b were equal to about 20% of the sectional

thickness t of tire tread portion 12, the effect would be that

the breaker plies would extend into the sidewalls. Further, if

the end portions 46a, 46b, 48a, 48b were to extend to a location

where t_a and t_b were about 35% of the maximum tire section

thickness t, the effect would be higher heat generation and

potential tire failure. On the other hand, if the tire breakers

are too narrow so that the ends are not close enough to the

sidewalls, the breaker plies do not provide the added stability

required to stiffen the tread and add strength to the casing.

The outermost breaker ply 46 has its end portions 46a and

46b disposed at a location where the thickness t_a and t_b of the

tread 43 is preferably between about 60% and about 85% of the

maximum tire thickness t. Correspondingly, the lower breaker

ply 48 has its ends 48a and 48b slightly longer than the plies

ends 46a and 46b of breaker ply 46. The ends 48a and 48b of

breaker ply 48 preferably extend somewhat longer than 46a and 46b of breaker ply 46 to prevent the formation of a hinge point

where the tire would naturally bend and generate additional

heat. The ends 48a and 48b of the lower breaker ply 48 extend

to a place where the thickness t_a and t_b is between 20% and to

about 45% less than the location of the ends 46a and 46b,

respectively, of upper breaker ply 46.

Locating the breaker plies 46 and 48 within the carcass

structure 22, shifts the deflection point of the tire 10 to a

location below the upper portions 14a, 16a, corresponding to the

shoulder portions of sidewalls 14, 16, respectively, to reduce

the heat generated. The location of the ends 46a, 46b, 48a, 48b

of the breaker plies 46, 48, respectively, result in a tire 10

where the heat buildup in the upper sidewall areas 14a, 16a does

not exceed a temperature at which the tire begins to breakdown.

Another advantage of the present design, as applied to a

H43.5X16.0-21 tire is that the number of carcass plies that

extend around the bead cores 50, 52, 54 has generally been

reduced, as compared to conventional prior art designs, to

twelve (12) plies.

An aircraft tire built in accordance with the present

invention, as illustrated in Figs. 1 and 2, was tested to meet

the standards set by the aircraft manufacturers . These are

generally known as double load requirements wherein, for

example, a tire rated for a load of 40,600 pounds can pass a test of a double load of 81,200 pounds at 210 pounds per square

inch (psi) pressure. Also, the tire must go through a series of

tests including 50 simulated take off cycles and eight taxi

cycles at the rate of load and inflation at 40 miles (mph) for

35,000 feet. Then the tire must go through two taxi cycles of

40 mph for 35,000 feet at 1.2 times the rate of load (40,600

pounds) . Further, the tire is subjected to one cycle of

simulated take off at 1.5 times the rate of load and finally one

simulated take off at 2 times the rate of load. The placement

of the breaker plies 46, 48 within the carcass structure 22, and

the sizing of the breaker plies so that their ends 46a, 46b,

48a, 48b are positioned at a location corresponding to a

predetermined percentage of the maximum thickness of the tread

portion 12, as previously discussed resulted in a tire which was

able to pass the double load test set forth above.

A series of other tire constructions, similar in size, i.e.

H43.5X16.0-21, to the disclosed tire construction, were also

tested. Each of the other tire constructions, as described

below, experienced a heat generated failure in the shoulder

area. These tested tire constructions include:

Tire

Construction Features

1 14 plies with 29 inch building drum width

2 14 plies high angle with a 29 inch building drum width 3 16 plies with a 29 inch building drum width

4 16 plies with a 29 inch building drum width

5 14 plies plus two breakers and one tread reinforcing tread ply with a 30 inch building drum width

6 14 plies plus two breakers, one tread ply and fabric sidewall inserts with a 30 inch building drum width

7 35 degree average carcass angle with 29.5 inch building drum width

8 14 plies plus two breakers and two tread reinforcing plies with a 28.5 inch building drum width

It is apparent that there has been provided in accordance

with this invention a pneumatic tire for an aircraft that

satisfies the objects, means and advantages set forth

hereinbefore. According to the invention, the pneumatic tire

for an aircraft meets the _. standards of the double load

requirement for aircraft tires and has breaker plies embedded

within a multi- layered carcass so that the ends of the breaker

plies are disposed at a location where the tread thickness is

between about 60% and 85% of the maximum thickness of the tread.

Also tread plies are incorporated in the tire and positioned so

that the ends are at a location corresponding to between about

60% and 85% of the maximum tire section thickness.

While the invention has been described in combination with

embodiments thereof, it is evident that many alternatives,

modifications, and variations will be apparent to those skilled in the art in light of the foregoing teachings. Accordingly,

the invention is intended to embrace all such alternatives,

modifications and variations as fall within the spirit and scope

of the appended claims .

Claims

What is claimed:

1. A pneumatic tire for an aircraft, comprising:

a multi-layered tire carcass composed of a plurality of ply

layers and a pair of spaced apart bead portions each having at

least two substantially inextensible bead cores disposed side by

side and spaced apart axially, the ply layers having carcass

plies extending circumferentially about the tire and extending

between the bead cores of opposite bead portions;

a tread portion overlying the multi-layered tire carcass;

a pair of sidewall portions extending from the bead

portions to the tread portion;

at least first and second breaker plies embedded within the

multi-layered carcass, and

the first and second breaker plies each having first and

second opposite ends disposed at a location where the tread

portion has a thickness of about 60% to about 85% of the maximum

thickness of the tread portion.

2. The pneumatic tire of claim 1 wherein the first and

second breaker plies each have first and second opposite ends

that are disposed at a location where the tread portion has a

thickness of about 60% to about 85% of the maximum thickness of

the tread portion.

3. The pneumatic tire of claim 1 wherein the first and

second breaker plies extend entirely about the circumference of the tire and the second breaker ply is longer than the first

breaker ply so that the opposite ends of the second breaker ply

are disposed closer to the pair of spaced apart bead portions

than the opposite ends of the first breaker ply.

4. The pneumatic tire of claim 3 wherein the first and

second opposite ends of the first breaker ply are disposed at a

location where the tread portion has a thickness of about 20% to

about 45% less than the thickness of the tread portion at the

location of the first and second opposite ends of the second breaker ply.

5. The pneumatic tire of claim 5 wherein the first and

second breaker plies are disposed adjacent each other.

6. The pneumatic tire of claim 5 further including third

and fourth breaker plies embedded within the multi -layer carcass

and each having first and second opposite ends disposed at a

location where the tread portion has a thickness of about 60% to

about 85% of the maximum thickness of the tread portion.

7. The pneumatic tire of claim 6 further including third

and fourth breaker plies embedded within the multi-layer carcass

and spaced from said first and second breaker plies by one or

more carcass plies each having third and fourth opposite ends

disposed at a location where the tread portion has a thickness

of about 60% to about 85% of the maximum thickness of the tread

portion.

8. The pneumatic tire of claim 1 wherein the first and

second breaker plies are abutted against each other.

9. The pneumatic tire of claim 8 further including a buff

line cushion between the multi-layered carcass and the tread portion.

10. The pneumatic tire of claim 1 wherein the ply layers

are rubberized laminated ply layers with each constructed of a

plurality of cords disposed at an angle ╬▒ in the range of about

25┬░ to about 50┬░ with respect to an equatorial plane through the tire.

11. The pneumatic tire of claim 1 wherein the maximum

thickness of the tread portion is measured at the equatorial

plane through the tire.

12. The pneumatic tire of claim 1 further including first

and second overlying tread plies disposed within the tread

portion, the ends of the first and second tread plies positioned

at a location corresponding to between about 60% and 85% of the

maximum tire section thickness.

13. The pneumatic tire of claim 12 wherein the tread ply

located close to the carcass is wider then the other tread ply.

14. The pneumatic tire of claim 1 including three

substantially inextensible bead cores disposed side by side and

spaced apart axially.