CA1099205A - Webbed non-pneumatic tire - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
There is disclosed a non-pneumatic tire for mounting on a rim having axially spaced mounting flanges.
The tire is formed with a radially exterior tread surface having axially outwardly sloped side walls projecting radially inwardly therefrom and formed on their radially inwardly extremities with shoulders that nest against the radially outward edges of the mounting flanges. Retaining flanges then project radially inwardly therefrom for re-tention on the axially inner sides of the mounting flanges.
The tread surface and opposite side walls co-operate to form a circumferential interior cavity in which a latticework of webbing is formed by axially extending interrupter webs which are spaced equidistance about such cavity and have an annular projecting band circumferentially thereabout and connected with such axially projecting interrupter webs.
The tread; sidewalls, flanges and webbing are all preferably constructed of resilient elastic material such as polyure-thane and have a circumferential length approximately 10%
less than the circumferential distance around the rim. This provides an elastic constraining force when the tire is stretched over the rim. Also, elastic endless belts or beads may be embedded in the retaining flanges to provide further securing force maintaining the tire on such rim.

Description

The present invention relates generally to tires and more particularly to uninflated tires mounted on con-ventional pneumatic rims.
Numerous attempts have been made to construct a satisfactory non-pneumatic tire, but, in spite of such efforts extending over many decades, there still exists a need for an inexpensive non-pneumatic tire having the performance characteristics normally associated with pneu-matic tires.
Early tires merely provided a coating of rubber on a rigid wood or metal wheel. Subsequent efforts led to resilient walled tires, not unlike pneumatic tires, wherein the walls had greater rigidity and structural supportive characteristics than that for pneumatic tires. Such tires had the shortcoming that they could not provide the desired weight support function while providing the necessary cushioning for the load being carried thereby.
Other efforts led to the provision of flexible walled tires having a central circumferentlal cavity filled with resilient foam or other cellular structure. These tires, likewise, met with dissatisfaction in that the foam or cellular structure frequently tended to break down after a relatlvely short service life. In addition, extreme difficulty was encountered with respec-t to retaining the tlres on the rims.
More racent efforts produced solid cross section tires of resilient non-cellular material but, again, diffi-culties have been encountered in retaining such tires on the rim. Further efforts have led to flexible wall tires having interior circumferential cavities extendin~ thereabout ~
with the cross sectional configuration of the walls of such tires being somewhat V-shaped with the apex thereof riding on the ground to provide somewhat o~ a bridge characteristic in transmitting the force on the tire rim to the tread surface making contact with the ground. A particular short-coming experienced in testing tires of this construction is that uninflated fle~ible wall tires of this type tend to build up somewhat of a bulge or wave immediately ahead of the point where the tire makes contact with the ground. This phenomenon, which may be referred to as a "standing wave", is the source of one of the major difficulties experienced in such tests. This may result in the tire crawling, or walking, around the rim at a rate proportional to the speed of rotation. The so called standing wave immediately ahead of the ground contact point, or "footprint" of the tire results in the tire attempting to climb such standing wave then encourltering rolling resistance. Further, the bulge tends to force the tire away from the rim on which it is mounted and such tendency is compounded when torque is applied to the rim. When a torque is applied to the loaded rim the bulge on the backside of the footprint is exagger-ated frequently resulting in a gap opening up between the tire and rim and sometimes results in the tire itself dismounting the rim when lateral forces are applied between such tire and rim, as for ins~ance during a turn of the front wheel or similar maneuver.

Efforts to solve this problem have led to testing various bonding materials for bonding the wall of the tire directly to the rim but with the present state of the ar-t, ~Lo~D49;2~

no such practical bonding materials have been found and even if such material were available, i-t would suffer the shortcoming that the aforementioned standing wave would still be devaloped to some degree and the absolute anchoring of the radially inner edge~ of the tire sidewalls to the rim to positively prevent shifting thereof would result in extreme shear stresses being applied to such tire as a result of such standing wave, thus rapidly fatiguing and deteriorating the tire itself.

Thus, there still exists a great demand for a non-pneumatic tire whicn may be easily and conveniently re-movably mounted on a conventional rim and which will provide the desired weight carrying function and cushioning during operation without building up a roll resisting standing wave ahead of the tire footprint and which will avoid accidental dismounting of the tire from the rim during operation.
The present invention is characterized by a tire formed with a r~dially outwardly facing tread surface and having radially inwardly and outwardly angled oppositely disposed side walls which engage the tire rim on the radially inward extremities thereof and is formed with radially inwardly extending retaining flanges received on the axially inner side of the rim mounting flange6, the space between the side walls forming an interior cavity. Formed within such interior cavity, is an array o~ webbing formed with axially extending interrupter webs which maintain the retaining flanges and side walls urged axially outwardly to prevent disengagement of the retaining flanges from the rim mounting flanges while providing a degree of flexing of such side walls and tread as each individual web passes between ~09g~

the rim and entire support surface. Such interrupter webs serve the further function of interrupting this tendency of the tire to build up a standing wave as the weiyhted rim and tire rotate over a support surface.
More specifically the invention is a non-pneuma~ic tire to be mounted on a rim with annular mounting flanges spaced apart a predetermined axial distance, said tire comprising: a resilient circumferential tread wall having a radially outwardly facing tread surface; a pair of axially spaced apart elastic sidewalls projecting radially inwardly from said tread wall and formed with shoulders to nest on said respective mounting flanges for bearing, in radial compression, a load on said rim and co-operating with said tread wall to form a circumferential cavity; a pair of axially spaced apart elastic annular retained flanges projecting radially inwardly from said respective sidewalls for being stretched over said rim mounting flanges to be held captive on the axially inner sides of said mounting flanges; and a plurality of radially projecting resilient axial interrupter webs spaced apart substantially equidis-tant about the circumference of said cavity, extendingaxially between said sidewalls and connected thereto through-out substantially the radial length of their respective opposi-te extremities, said webs being flexible in their respective axial plane to yieldingly support said sidewalls against collapse axially inwardly from said mounting flanges.
The tire may also incorporate an endless annular elastic band extending about such circumferential cav:ity and connected with each of the axially extending webs to support such webs against buckling as the side walls and retaining flanges are urged axially inwardly thereag~inst as they perform their weight support function. A150, endless elastic belts may be embedded in the retaining flanges to co-operate with such flanges and the side walls in resisting radially outwardly expansion of the tire during high speed operation and resultant disengagement of the tire~from the rim.
Aspects of the invention are illustrated, merely by way of example, in the drawings, in which:

Figure 1 is a partial cut away perspective view of a tire of the present invention mounted on a rim;
Figure 2 is a partial cut away perspective view, in enlarged scale, of a portion of the tire shown in Figure l;
Figure 3 is a partial interior view looking radially outwardly from the bottom of the section of tire shown in Figure 2;
Figure 4 is a sectional view, taken through a modification of the tire shown in Figure l;

: 20 Figure.5 is a radial sectional view taken along the line 5-5 of Figure 2;
Figure 6 is a partial side view of a second embodiment of the non-pneumatic tire of the present in-vention;

Figure 7 is a transverse sectional view taken along the line 7-7 of Figure 6;
Figure 8 is a transverse sectional view o~ a third embodiment of the non-pneumatic tire of the present in-vention; and Figure 9, which is on the first sheet of drawings,

2~

is a transverse sectional view of a fourth embodiment of the non-pneumatic tire of the present invention.
The non-pneumatic tire 10 (Figure 1) of the present invention is intended to be mounted on a wheel, such as a conventional bicycle wheel 12, which may be a central hub 14 carried central of such wheel by means of bicycle spokes 16. Referring to Fi~ure 2, the tire 10 includes, generally, a radially outer tread wall 68 having a radially outwardly facing tread surface 30 and angles axially out-wardly in opposite directions and radially inwardly to formoppositely angling side walls 26 and 28 which then turn to project radially inwardly to terminate in oppositely disposed retaining flanges 20 and 22. The tread wall 68, opposite side walls 26 and 28, and retaining ~langes 20 and 22 co-operate to form a circumferential cavity 36 which is separatedinto discrete segments by means of resilient radially extending interrupter webs 40 which are circumferentially spaced equidistant about such cavity 36 to be disposed in spaced apart axial planes and co-operate with a central radially projecting elastice support band 42. The tire 10 is preferably constructed of an elastomer such as polyure-thane and, in its relaxed position of the circumference, is about 90% that of the rim 12 such that the tire itself and suppoxt web 42 will be maintained in a stretched position on such rim to provide structural integrity of the tire and maintain it on such rim. Preferably elastic nylon belts or beads 56 and 58 are embedded in the reta.ining ~langes 20 and 22 to provide retaining forces for retaining such tire on the rim 12.
While the tire 10 may take many different configura~

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tions, it is important that it be hollow t~ form the circum-ferential cavity 36 and that the webs 40 be spaced equidis-tant about such cavity and connect on their axial opposite ends with the retaining flanges 20 and 22 and with the side walls 26 and 28 to restrict against collapse thereof when weight is applied to the rim 12. The elastic annular band 42 is conveniently joined on its radially outer extremity with the tread wall 68 and projects radially inwardly to the annular plane of the radially inner edges of the webs 40.

Referring to Figure 2, the exterior surfaces of the side walls 26 and 28 slope axially outwardly radially inwardly and at their radially inner extremities, turn axially inwardly to form ears or lobes 41 and 43, resp~ct-iv,ely and then cup radially inwardly to form radially inwardly openi~y nesting shoulders 45 and 47, which nest against the rounded radially outward extremities of the . respective opposite rim flanges 72 and 74 (Figure 1), of the ; rim 12O
Still referring to Figure 2, the interior cavity 36 is formed in its radlally outward extremity with opposite outer surfaces 44 and 46 which angle axially outwardly and radially inwardly to then turn and extend generally radially inwardly to form oppositely disposed side surfaces 48 and 50 defining the interior surfaces of the portion of the side walls 26 and 28 and also of the retaining flanges 22. With continued reference to Fi.gure 2, in the particular molding procedure employed for molding.khe tire 10, stand-off supports are employed for supporting the elastic beads 56 and 58 in the mold thus leaving windows 60 in the radially inner edges 62 and 64 of the retaining flanges 20 and 22 ~g~5 which exposes the elastic beads 56 and 58. Since this particular feature serves no important part of the tire of -~ the present invention, it will not be discussed further. The elastic nylon belts 56 and 58 in the preferred embodiment have a tensile strength of 270 lbs/sq inch.
While the minimum number of axially extending interrupter webs ~0 necessary for operation of the tire of the present invention has not been specifically determined, tests have been conducted which reveal that for a conven-tional 27 inch diamèter 10 speed bicycle tire, the number ofwebs 40 should be no less than 16.
Such tires employing sixteen e~ually spaced webs have been tested with success and it is believed that webs at less than 22.5 degrees apart for a 27 inGh diameter wh,eel would not per~orm satisfactorily. In the preferred embodi-ment 72, such webs 40 are spaced equidistant about the circumference of the cavity 36l thus placing such webs at 6 degree intervals thereby ~orming 72 compartments, generally designated 70,-having the opposite angular ends thereof formed by the webs 40 and *he radially outer walls thereof formed by the tread wall 68 and the axially opposite walls ~ormed by the side walls 26 and 28 and flanges 20 and 22.
With this arrangement, three of such webs 40 are flexed at all times when the rim is loaded with a somewhat standard weight of 50 pounds or more.
The tire 10 shown in Figures 4 and 5 is essen-tially the same as that shown in Figure 1, except that the opposite side walls 26' and 28' are formed to pro~ect axially ou-twardly and radially inwardly Erom the tread wall 30' and to ha~e their medial portions bulge somewhat out-wardly and then to form the lobes 41' and 43' at their radially inward extremities with somewhat of a more curved appearance and then to form the nesting shoulders 45' and 47' of their axially inward extremities. Gripping ribs 52 and 54 are formed in the axially outer walls of the re-taining flanges 20' and 22' for engagement with the res-pective interior surfaces 76 and 78 of the rim mounting flanges 72 and 74.
In operation, when it is desired to mount the non-pneumatic tire of the present in~ention on a conventional bicycle rim 12, it is only necessary to remove the con-ventional pneumatic tire and the tire 10 of the present invention may be stretched onto such rim Since the tire 10 for a 27 inch rim is only about 24 inches in diameter in its relaxed position, significant stretching thereof is necessary to mount the tire on the rim 12. This can easily be accomplished by positioni.ng the retaining flanges 20 and 22 along the side thereof within the rim flanges 72 and 74 and then threading such tire onto the rim about the re-mainder of the periphery of such rim while holding thealready mounted portion on the rim. This can be accom-plished by merely extending a flat tool entirely across the radially outer extremities of the rim flanges 72 and 74 thus stretching the entire tire, includins the elastic beads 56 and 58, as the tool is advanced about such rim 12. In this regard, it is important that the belts 56 and 58 have a relaxed circum~erence significantly less than that for the radially outer extremities of the mounting ~langes 72 and 74 to thus cause such elastic belts 56 and 58 to resiliently ~gz~

hold the flanges 20 and 22 retained interiorly behind -the rim mounting flanges 72 and 74. A relaxed circumference of about 90~ of this maximum rim flan~e circumference has been found acceptable for polyurethane having a Shore hardness of 65 on the A scale to provide for betw~en 7 and 10~ elonga-tion upon stretch for mounting on the rim 12.
Once the tire 10 has been mounted on the rim 12, the supported bicycle is ready to be ridden. As weight is applied to the hub 14 and through the spokes 16 to the rim 12 and, consequently to the tire 10, the weight on such rim will act downwardly thereon and against the xespective shoulders 45 and 47 formed by the inner extremities of the side walls 26 and 28. It will be appreciated that the force of such weight will, because o~ the axially outwardly and radially inward slope of the side walls 26 and 28, tend to bulge the medial portions of such side waIls 26 and 28 axially outwardly. Such a~ial outward flexing of the central portion of such side walls 26 an~ 28 will be res-isted by the tensile strength of the interrupter w~bs 40 as such webs pass between the rim and supporting surface therefor. Further, since the elastic band 42 is under significant tension, it will serve to hold the medial portions of such webs 40 in the same axial plane as the axially outer extremities thereof, thus preventing buckling or torqueing thereof and consequent axially inward fléxing of the retaining flanges 20 and 22 causing them to pull away from the rim mounting flanges 72 and 74.
Experimentation has proven that the interrupter webs 40 perform even greater functions than resisting the s tendency of the medial porkions of the side walls 26 and 28 to flex outwardly upon loading thereof and in maintaining the mounting 1anges 20 and 22 urged outwardly against the mounting flanges 72 and 74 of the rim 10. This important feature, while not being entirely understood, is of great importance in retaining the tire 10 on the rim 12 during operation of such tire at higher speeds. Studies of non pneumatic bicycle tires and the like have shown that there is a tendency for the loaded tire to squat somewhat as it passes between the rim and supporting surface thus flatten~
ing the tread area and forming what is commonly referred to as a footprint. The size of this footprint is directly -proportional to the weight being carried on the tire and is '~
increased when the flexibility of the tire is increased. As a result of such squatting of the tire, somewhat of a bulge is created both forwardly and rearwardly of the footprint, which develops a tendency in the tire to separate from -the rim, particularly at highex speeds~ At lower speeds, the bulges are normally symmetrical forwardly and rearwardly of the footprint but when a torque is being applied to the whael hub 14 (Figure 1), the bulge rearwardly of -the foot print in the past has typically become even greater than that forwardly of the footprint, thus increasing the resis-tance to rolling of the rim and decreasing the efficiency of the tire. The bulge forwardly of the footprint, commonly referred to as a "standing wave", has in prior art tires frequently resulted in separation of the tire from the rim creating a gap between the tire and rim and, in many lnstances, resulting in unintentional dismounting of the tire from the rim. This is one of the problems that the tire of the ~9z~ ~

present invention overcomes.
The interrupter webs 40, as they pass between the rim and support surface, serve -to interrupt this standing wave eliminating the tendency of the tire to dismount itself at higher speeds. As mentioned hereinabove, the particular phenomenon of the interrupter webs 40 in minimizing, or even eliminating, such standing wave is not fully understood, but it is believed that the axial resistance provided by such webs to axially outward squatting of the side walls 26 and 28 serve to interrupt the tendency of the resilient polyure-thane to flow along the rim forwardly and rearwardly of the footprint, thus preventing a buildup of the standing wave and consequent walking of the tire around the rim.
Referring to Figure 4, it will be appreciated that lS the elastic annular band 42 serves to tie the central portions of the interrupter webs 40 together and co-operates with the side walls 26' and 28' to form what may be referred to as individual torsion boxes which provide yielding support for the rim 12. The annular band 42, when weight is applied directly over the hub 14, has its longer cross sectional dimension disposed centrally beneath such weight to co-operate with the side walls 2~' and 28' and webs 40, in yieldingly resisting radially inward flexing of the tread wall 68'.
During cornering, when a lateral force L (Figure 4), is applied to the tread surface 30' relative to the rim 12, the side walls 26' and 28' will be flexed causing the elastic band 42 to bend out of the vertical plane 80 of the rim 12, thus allowing the compressive force C to bend the annular dimension of such band 42 even farther, thus reducing ~)9~

the distance between such lateral ~orce L and the bead 58' on the outside of the corner being turned. This reduces the lever arm between such lateral force L and the elaskic bead 58', thus reducing the ~orce tending to stretch such bead 58' and lessens the tendency to expand such bead to a point where it may exceed the diameter of ~he outside rl~ mounting flange 74, and freeing the retaining flange 22 to escape from the interior of such mounting flange 74. It will be appreciated that this tendency of the tire to squat depends on the flexibility of the material from which such tire is constructed. For the polyurethane incorporated in the tire shown in Figure ~, a 75 5hore hardness on the "A" scale has been found pre~erable. For other lower profile tires having a lesser distance between the rim and exterior tread surface 30, a Shore hardness as low as 65 on the "A" scale has been found desirable.
The non-pneumatic tire shown in Figure 6 is similar in construction to the tire shown in Figures 1 through 5, except that it incorporates exterior traction ribs 84 (E'igure 7) that not only act to resist collapse of the side walls 26 and 28 when weight is applied thereto, but provide the additional feature of enhancing the traction of the tire when operating in a soft terrain or during co-rnering thereof. It will be appreciated that the webs 84 which are on an axial plane, bulge outwardly away from the outwardly and radially inwardly sloping side walls 26 and 28 to thus provide so~lewhat of a beam like construction res-isting collapse of such wall as weight is applled there-to.
The non-pneurnatic tire 90 shown in Figure 8 is 9~

also similar to tire shown in Figures 1 through 5 except that it is somewhat of a lower pro~ile having a shorter distance between the rim and tread surface 92 and provides ~or interior and exterior grippin~ of the mounting flanges 114 and 166 o~ the bicycle tire rim 115. The tire 90 includes a radially outwardly disposed circumferential tread wall 92 and is formed with radially i.nwardly and axially outwardly curved side walls 94 which terminate at their axially inward extremities in respective axially inwardly facing central grooves which fit over the exterior edges of the mounting flanges 114 and 116 and define respective anterior and exterior retaining flanges 98, 100, 102, and 104. Also, interior and exterior elastic belts 106, 108, 110 and 112 are embedded within the respective retaining flanges for resisting e~pansion of such tire and possible dismounting from the rim. The interrupter webs 122 are comparable to the webs 40 and the annular elastic support band 124 is comparable to the support band 42 shown in Figure 4.
Consequently, the tire shown in Figure 3 is similar to the tire shown in Figures 1 through 5 except that it is a somewhat lower pro~ile and provides for interior and exterior retaining flanges and elastic beads.
The tire shown in Figure 9 is similar to the tire shown in Figure 4 except tl~at it includes a central radial band 131 projecting radially inwardly beyond the radial inner extremities o~ the side flang~s 20' and 22', and is enlarged in cross-section on its radial inner extremity to form a circular conduit 133 having a rigid metallic bead 135 telescoped therethrough. Interrupter web 137 are spaced zl~

equidistant about the ci~cumference of the tire and taper axially downwardly and inwardly from the flanges 20' and 22' to join with the radial inner extremity of the band 131.
From the foregoing, it will be apparent that the non-pneumatic tire of the present invention is of hollow construction, thus minimizing the use of the petroleum base products that may be used in the polyurethane from which it may be constructed and provides for performance comparable to a pneumatic tire while relieving the problems normally connected with non-pneumatic tires as related to accidental dismounting thereof with resistance to rolling.

Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. A non-pneumatic tire to be mounted on a rim with annular mounting flanges spaced apart a predetermined axial distance, said tire comprising:
a resilient circumferential tread wall having a radially outwardly facing tread surface;
a pair of axially spaced apart elastic sidewalls projecting radially inwardly from said tread wall and formed with shoulders to nest on said respective mounting flanges for bearing, in radial compression, a load on said rim and co-operating with said tread wall to form a circumferential cavity;
a pair of axially spaced apart elastic annular retained flanges projecting radially inwardly from said respective sidewalls for being stretched over said rim mounting flanges to be held captive on the axially inner sides of said mounting flanges; and a plurality of radially projecting resilient axial interrupter webs spaced apart substantially equidistant about the circumference of said cavity, extending axially between said sidewalls and connected thereto throughout substantially the radial length of their respective opposite extremities, said webs being flexible in their respective axial plane to yieldingly support said sidewalls against collapse axially inwardly from said mounting flanges.

2. A non-pneumatic tire as claimed in claim 1 further including an annular elastic stabilizing band disposed centrally in said cavity, centrally between said sidewalls, connected with the axially central portion of said webs, and of a circumference sufficient to be held under tension when said tire is mounted on said rim mounting flanges whereby said tire may be mounted on said rim with said retaining flanges retained between said mounting flanges and urged yieldingly thereagainst by said webs and when weight is applied to said rim while said tire rolls on a support surface said sidewalls will carry said weight and when said webs pass sequentially between said rim and support surface they will co-operate with said sidewalls to provide irregular support.

3. A non-pneumatic tire as claimed in claim 1 wherein said retained flanges are formed with a relaxed circumference of about 90% of the radially outer edge of said mounting flanges.

4. A non-pneumatic tire as claimed in claim 1 wherein said side walls diverge radially inwardly and axially outwardly from said tread wall and co-operate therewith to form a V-shaped cross section.

5. A non-pneumatic tire as claimed in claim 1 wherein said retained flanges terminate in respective annular inner edges spaced radially outwardly from said rim.

6. A non-pneumatic tire as claimed in claim 1 wherein said band is a single annular band and said webs are spaced radially apart a distance sufficient to co-operate with said annular band and side walls to form on the oppo-site sides of said band radially elongated cells.

7. A non-pneumatic tire as claimed in claim 1 in which said axial webs project radially inwardly from said tread wall to terminate in radially inner edges substantially coextensive with the radially inner extensions of said retained flanges.

8. A non-pneumatic tire as claimed in claim 1 that includes endless beads embedded in said retained flanges and having less elasticity than said retained flanges.

9. A non-pneumatic tire to be mounted on a rim formed with axially spaced apart annular mounting flanges, said tire comprising:
a flexible circumferential tread wall having a radially outwardly facing tread surface;
a pair of axially spaced apart flexible elastic load-bearing sidewalls, projecting radially inwardly from said tread wall and formed with annular radially inwardly facing shoulders for seating on the radial outer edges of said rim-mounting flanges, said tread and sidewalls co-operating to form a circumferential cavity;
a pair of axially spaced apart retained flanges projecting radially inwardly from said respective sidewalls and beyond said shoulders for receipt between the axially inner sides of the rim-mounting flanges; and a plurality of thin radially projecting, flexible axial webs disposed about the circumference of said cavity, connected throughout the radial length of their opposite extremities with said sidewalls to yieldingly urge said retained flanges axially outwardly, said webs being spaced apart a circumferential distance sufficient to co-operate with said side walls to form separate, individual, cir-cumferentially elongated compartments causing said sidewalls intermediate said wecbs to flex axially outwardly under load an amount substantially greater than at said extremities of said webs, to thus cause said webs to interrupt the con-tinuity in degree of flexing of said sidewalls under load.

10. A non-pneumatic tire as claimed in claim 9 wherein said retained flanges are formed with a relaxed circumference of about 90% of the radially outer edges of said mounting flanges.

11. A non-pneumatic tire as claimed in claim 9 wherein said side walls diverge radially inwardly and axially outwardly from said tread wall and co-operate therewith to form a V-shaped cross section.

12. A non-pneumatic tire as claimed in claim 9 wherein said retained flanges terminate in respective annular inner edges spaced radially outwardly from said rim.

13. A non-pneumatic tire as claimed in claim 9 including a resilient annular band disposed centrally in said cavity and joined with the axially intermediate portion of said webs to stabilize said webs against shifting out of alignment in their respective axial planes.

14. A non-pneumatic tire as claimed in claim 9 wherein said axial webs project radially inwardly from said tread walls to terminate in radially inner edges substan-tially co-extensive with the radially inner extremities of said retained flanges.

15. A non-pneumatic tire as claimed in claim 14 wherein said retained flanges terminate in respective annular, radially inner edges spaced radially outwardly from said rim.