AU2011213820B2

AU2011213820B2 - Improvement in Motorcycle Tyres

Info

Publication number: AU2011213820B2
Application number: AU2011213820A
Authority: AU
Inventors: Robert Sohn
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-09-22
Filing date: 2011-08-23
Publication date: 2012-04-19
Anticipated expiration: 2031-08-23
Also published as: AU2011213820A1

Abstract

-12 A profile for a motorcycle tyre; said profile including an external wall profile and an internal wall profile; said external wall profile including a central section conforming substantially to a segment of a cylinder and two symmetrically located side sections at either side of said central section; said side sections extending substantially tangentially outwardly from said central section; said internal wall profile conforming substantially to a segment of a cylinder and wherein a cylindrical form of said internal wall profile is at least coextensive with said central section and said side sections of said external wall profile such that said internal wall profile maintains a substantially cylindrical shape extending from proximate one rim bead to proximate an opposite rim bead. 20) FigS3 Fig 4

Description

P100/009 Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION invention Title: IMPROVEMENT IN MOTORCYCLE TYRES The invention is described in the following statement, including the best method of performing it known to us: Our Ref: 112025 - 2 IMPROVEMENT IN MOTORCYCLE TYRES The present invention relates to motorcycle tyres and, more particularly, to racing tyres for motorcycles. 5 BACKGROUND Motorcycle racing, and in particular, Grand Prix motorcycle racing is made particularly dangerous because of the high speeds which riders try to maintain while 10 negotiating bends in the racing circuit. To' maintain the highest speeds possible, the motorcycle must assume an inclination of the plane of the motorcycle to the track so as to cancel the high centrifugal forces generated. This inclination of the plane 15 of the cycle dictates that the vector of the centrifugal force directed along the median plane of the cycle, no longer passes trough the contact area of the tyre with the track. Friction at the area of contact is likewise reduced proportionally to the degree of inclination as the weight 20 of the motorcycle and rider acting at the area of contact is also reduced. Racing motor cycle tyre8 are substantially cylindrical in section for the greater part of the tyre section. This minimizes the contact area, and hence rolling resistance, 25 of the tyre whether the cycle is upright when moving in a straight line or inclined when cornering, For the same - 3 reason, racing tyres are generally smooth with no significant tread, relying instead for traction on specially formulated rubber properties and inflation pressures, Small contact area and no, or minimal tread, are 5 desirable for minimising rolling resistance, but become a disadvantage at extreme cornering angles. The dynamics of a tyre's area of contact with a track surface when cornering, the effect of torque delivered to the tyre while the rear wheel is not facing precisely in the direction of travel, 10 are extremely complex and cannot be treated here, however the typical tyre profile and these dynamic interactions, not infrequently result in the tyre breaking contact with the surface with potentially disastrous results. It is an object of the present invention to address or 15 at least ameliorate some of the above disadvantages, Notes 1. The term "comprising" (and grammatical variations thereof) is used in this specification in the inclusive 20 sense of "having" or "including", and not in the exclusive sense of "consisting only of". 2. The above discussion of the prior art in the Background of the invention, is not an admission that any information discussed therein is citable prior art or 25 part of the common general knowledge of persons skilled in the art in any country.

BRIEF DESCRIPTION OF INVENTION Accordingly, in first broad form of the invention, there is provided a profile for a motorcycle tyre; said profile including an external wall profile and an internal 5 wall profile; said external wall profile including a central section conforming substantially to a segment of a cylinder and two symmetrically located side sections at either side of said central section; said side sections extending substantially tangentially outwardly from said 10 central section; said internal wall profile conforming substantially to a segment of a cylinder and wherein a cylindrical form of said internal wall profile is at least coextensive with said central section and said side sections of said external wall profile such that said 15 internal wall profile maintains a substantially cylindrical shape extending from proximate one rim bead to proximate an opposite rim bead. Preferably, said side sections of said external profile form substantially straight lines extending from 20 ends of said central section. Preferably, said side sections of said external profile form shallow convex curves extending from ends of said central section. Preferably, said side sections of said external 25 profile subtend an angle of approximately 90degrees symmetrically about the median plane of a motorcycle wheel. Preferably, each of said side sections of said external profile is provided with a tread pattern; either one of said tread patterns coming into contact with a 30 supporting road or track surface when said median plane is inclined at an angle equal to or less than 45degrees to said supporting road or track surface. Preferably, said contact area between a said side section of said external profile and said road or track surface is greater than between said central section and said road or track service, when said median plane is inclined at an angle equal to or less than 45degrees. In another broad form of the invention, there is 5 provided a method of increasing an area of contact between a motorcycle and a track or road surface when said motorcycle negotiates a bend in said track or road; said method includes providing a motorcycle tyre with a tripartite external profile; said external profile divided 10 into a central section and two side sections; said side sections extending tangentially outwardly from said central section, and wherein an internal wall profile of said motor cycle tyre conforms substantially to a cylindrical section extending substantially from proximate one rim bead of said 15 tyre to proximate an opposite rim bead. Preferably, said central section of said external profile comprises a portion of a generally cylindrical section; said side sections comprising generally straight lines extending tangentially from either side of said 20 central section. Preferably, said two side sections subtend an angle of approximately 90degrees; said side sections symmetrical about a median plan of a motorcycle wheel. Preferably, said two side sections are provide with a 25 tread pattern; either one of said two side sections coming into contact with said track or road surface when a median plane of said motorcycle is inclined at an angle equal to or less than 45degrees to said track or road surface. 30 BRIEF DESCRIPTION OF DRAWINGS - - 6 ~ Embodiments of the present invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a simplified typical profile and cross 5 section of a motorcycle racing tyre according to prior art oriented as in straight running, Figure 2 shows the tyre of figure 1 in an attitude assumed during hard cornering, Figure 3 shows a motorcycle tyre profile according to 10 a preferred embodiment of the invention also oriented as in straight running, Figure 4 shows the motorcycle tyre of figure 3 in hard cornering where the inclination of the median plane of the motorcycle wheel is at an inclination of 45degrees. 15 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference to figure 1, a typical motorcycle racing tyre 10 has a profile 12, the larger portion of which is substantially in the form of a cylindrical 20 section, It can be seen from figure 2, that during hard cornering, the area of contact 14 between the tyre 10 and the road or track surface 16 is substantially the same as it is during the substantially straight line movement of figure 1. 25 The force "F" from the weight of the motorcycle acting on the area of contact 14 is reduced due to the angle of - 7 inclination of the motorcycle when cornering. Consequently friction between the area of contact 14 and the surface is also significantly reduced. It may then take only a small jerking of the motorcycle suspension, or brief contact of 5 the rider's knee with the surface, for traction to be lost leading to loss of control of the machine. Turning now to figures 3 and 4, a racing motorcycle tyre 20 according to a preferred embodiment of the present invention, has a profile with a central section 22, similar 10 in profile to that of the typical tyre shown in figures 1 and 2. In this case however, there are two side sections 24 and 26 respectively at either side of the central section 22, Preferably, side sections 24 and 26 extend outwardly 15 and are substantially tangential to the arcuate form of the central section 22. Again preferably, side sections 24 and 26 form substantially straight lines, although they may have a shallow convex curvature. Again preferably, the angle subtended by the two side 20 sections 24 and 26 is approximately 90degrees, with the side portions symmetrical about the median plane 28 of the motorcycle~ wheel (not shown) . With this angle, it can be seen that as the motorcycle heels over in cornering, the side section 26 (in the example of figure 4) comes into 25 contact with the road or track surface 16 when the inclination of the median plane 28 reaches approximately - 8 45degrees, thereby increasing significantly the contact area between the tyre 20 and the surface 16. With flexure of the side wall of the tyre, contact between the side section 26 and the surface will be maintained for all 5 practical purpose for angles less than 45degrees. Preferably, side sections 24 and 26 are provided with a tread pattern 30 which is adapted- to countering the centrifugal force "CF" acting at the area of contact between the side section and the road or track surface. The 10 combination of greater contact area and suitable tread pattern provides a significant reduction in the likelihood of loss of traction and loss of control when a motorcycle assumes an extreme angle of 45degrees or less during cornering. 15 The above describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention. 20

Claims

1. A profile for a motorcycle tyre; said profile including an external wall profile and an internal wall profile; said external wall profile including a central section conforming substantially to a segment of a cylinder and two symmetrically located side sections at either side of said central section; said side sections extending substantially tangentially outwardly from said central section; said internal wall profile conforming substantially to a segment of a cylinder and wherein a cylindrical form of said internal wall profile is at least coextensive with said central section and said side sections of said external wall profile such that said internal wall profile maintains a substantially cylindrical shape extending from proximate one rim bead to proximate an opposite rim bead.

2. The profile of claim 1 wherein said side sections of said external profile form substantially straight lines extending from ends of said central section.

3. The profile of claim 1 wherein said side sections of said external profile form shallow convex curves extending from ends of said central section.

4. The profile of any one of claims 1 to 3 wherein said side sections of said external profile subtend an angle -10 of approximately 90degrees symmetrically about the median plane of a motorcycle wheel.

5. The profile of any one of claims 1 to 4 wherein each of said side sections of said external profile is provided with a tread pattern; either one of said tread patterns coming into contact with a supporting road or track surface when said median plane is inclined at an angle equal to or less than 45degrees to said supporting road or track surface.

6. The profile of claim 5 wherein said contact area between a said side section of said external profile and said road or track surface is greater than between said central section and said road or track service, when said median plane is inclined at an angle equal to or less than 45degrees.

7. A method of increasing an area of contact between a motorcycle and a track or road surface when said motorcycle negotiates a bend in said track or road; said method includes providing a motorcycle tyre with a tripartite external profile; said external profile divided into a central section and two side sections; said side sections extending tangentially outwardly from said central section, and wherein an internal wall profile of said motor cycle tyre conforms substantially -11 to a cylindrical section extending substantially from proximate one rim bead of said tyre to proximate an opposite rim bead.

8. The method of claim 7 wherein said central section of said external profile comprises a portion of a generally cylindrical section; said side sections comprising generally straight lines extending tangentially from either side of said central section.

9. The method of claim 8 wherein said two side sections of said external profile subtend an angle of approximately 90degrees; said side sections symmetrical about a median plan of a motorcycle wheel.

10. The method of any one of claims 7 to 9 wherein said two side sections are provide with a tread pattern; either one of said two side sections coming into contact with said track or road surface when a median plane of said motorcycle is inclined at an angle equal to or less than 45degrees to said track or road surface.

11. A profile for a motorcycle as hereinbefore described and with reference to figures 3 and 4 of the drawings.