GB2571980A

GB2571980A - Tyre assembly with protective insert

Info

Publication number: GB2571980A
Application number: GB1804173.1A
Authority: GB
Inventors: Boyd Alan; Mcmullan Dale
Original assignee: CHAIN REACTION CYCLES Ltd
Current assignee: CHAIN REACTION CYCLES Ltd
Priority date: 2018-03-15
Filing date: 2018-03-15
Publication date: 2019-09-18
Anticipated expiration: 2038-03-15
Also published as: GB201804173D0; GB2571980B

Abstract

A tyre assembly (fig 1, 10) comprises a wheel rim 12, a tyre 14 fitted to the wheel rim 12, and an annular insert 40 located inside the tyre 14 around the rim 12. In a rest state, the annular insert is diametrically larger than the rim. The annular insert is formed from a compressible material that causes it to contract diametrically in response to inflation of said tyre such that it shrinks it to the rim. The annular insert 40 is easy to fit and protects against pinch punctures, rim damage and de-seating of the tyre beads. Further feature may include a valve (fig 12, 32), with a valve head (52), having a fluid channel (60), and having an opening at the face of the valve in a radial direction.

Description

Field of the Invention

The present invention relates to pneumatic tyres, and in particular to protective inserts for pneumatic tyres.

Background to the Invention

A pneumatic tyre assembly comprises a tyre fitted to a wheel rim and filled with a pressurised fluid, typically air. The pressurised air may be contained within an inflatable tube located within the tire, or may be contained by the tyre itself, i.e. the tyre may be “tubeless”.

Pneumatic tyres are susceptible to pinch puncturing, whereby the side wall of the tyre deforms under loading to the extent that it punctures upon being pinched against the wheel rim. In addition, whether or not the tyre punctures, the deformation of the tyre can allow the wheel rim to be damaged when the tyre impacts against a hard surface. The likelihood of a pinch puncture or rim damage occurring depends on a number of factors including the fluid pressure within the tyre, the strength of the side walls and the load exerted on the tyre during use.

The problems outlined above are particularly, but not exclusively, prevalent in tyre assemblies for bicycles. The problems are exacerbated in the case of mountain bikes, where riders may prefer to ride with a below-rated fluid pressure in the tyre.

It is known to address these problems by providing a protective tyre insert inside the tire. Conventionally, the protective insert is configured to fit elastically to the wheel rim. This is problematic because, not only can the insert be awkward to fit to the wheel rim, but once the insert is fitted it is difficult to fit the tyre to the wheel rim, and a special fitting tool is required for this purpose.

It would be desirable to address the problems outlined above.

Summary of the Invention

A first aspect of the invention provides a tyre assembly comprising:

a wheel rim;

a tyre fitted to the wheel rim; and an annular insert located inside said tyre around said rim, wherein, in a rest state, said annular insert is diametrically larger than said rim, and wherein said annular insert is formed from a compressible material that causes said annular insert to contract diametrically in response to inflation of said tyre.

A second aspect of the invention provides an annular tyre insert formed from a compressible material that causes a diametric size of said insert to change depending on ambient fluid pressure. Advantageously, said annular insert is configured to contract diametrically in response to elevation of fluid pressure around said insert.

Advantageously, the compressible material causes said annular insert to contract diametrically in response to fluid pressure above atmospheric pressure.

In preferred embodiments, the tyre insert is shaped and dimensioned for location inside a tyre around a wheel rim, and wherein, in a rest state, said annular insert is diametrically larger than said rim.

Said compressible material is preferably a cellular material, preferably a closed cell material. Said compressible material is preferably a polymeric material, for example a foam or rubber.

In preferred embodiments, said annular insert is semi-rigid. Preferably, said annular insert has a solid core.

Advantageously, said annular insert is configured to contract diametrically to engage with said rim in response to inflation of said tyre. It is preferred that said annular insert is configured to contract diametrically to fit tightly around said rim in response to inflation of said tyre.

In said rest state said annular insert is loose-fitting around said rim. In preferred embodiments, in said rest state said annular insert is loosely located inside said tyre and around said rim.

Typically, said annular insert is dimensioned such that, when the annular insert is in its rest state, and the tyre and the insert are concentric, there is an annular gap between an inner surface of a tread portion of the tyre and the annular insert. Typically, said annular insert is dimensioned such that, when the annular insert is in its rest state, and the rim and the insert are concentric, there is an annular gap between an inner surface of the annular insert and the rim.

Preferably, in a contracted state of the annular insert, a respective part of the insert is located over each edge of the rim. Said annular insert may include a respective lateral protrusion extending at least partly, and preferably fully, around the insert in a circumferential direction. The respective lateral protrusion may be located over the respect edge of the rim.

The tyre assembly may include a valve having a valve head that includes at least one fluid channel that opens at a face of the valve head that is oblique or perpendicular to the radial direction of the rim when the valve is fitted to the rim. The valve head typically has a front face, first and second side faces, and first and second end faces, wherein, when the valve is fitted to the rim, the front face faces radially away from the rim, the side faces face substantially laterally with respect to the rim, and the end faces face substantially tangentially with respect to the rim, and wherein said at least one fluid channel opens at any one or more of said side or end faces. Said at least one fluid channel may comprise a groove formed in the valve head, and said groove typically runs substantially perpendicular with the radial direction of the rim.

A third aspect of the invention provides a valve having a valve head that includes at least one fluid channel that opens at a face of the valve head that is oblique or perpendicular to a radial direction of a wheel rim when the valve is fitted to the rim.

Further advantageous aspects of the invention will be apparent to those ordinarily skilled in the art upon review of the following description of a specific embodiment and with reference to the accompanying drawings.

Brief Description of the Drawings

An embodiment of the invention is now described by way of example and with reference to the accompanying drawings in which:

Figure 1 is a side view of a tyre assembly embodying one aspect of the invention, including a protective insert embodying another aspect of the invention;

Figure 2 is a sectioned end view of the tyre assembly of Figure 1, showing the protective insert in a rest state;

Figure 3 is a detail of the sectioned end view of Figure 2 with the protective insert in the rest state;

Figure 4 is an isometric view of the protective insert in its rest state;

Figure 5 is a transverse cross-sectional view of the protective insert of Figure 4;

Figure 6 is a sectioned end view of the tyre assembly of Figure 1, showing the protective insert in a contracted state;

Figure 7 is a detail of the sectioned end view of Figure 6 with the protective insert in the contracted state;

Figure 8 is a detail of a sectioned end view of the tyre assembly, showing a valve section of the tyre assembly and showing the insert in the rest state;

Figure 9 is a side view of the detail of Figure 8;

Figure 10 is a detail of the sectioned end view of Figure 8 showing the insert in the contracted state;

Figure 11 is a side view of the detail of Figure 10;

Figure 12 is a perspective view of a valve for use with the tyre assembly;

Figure 13 is a plan view of the valve of Figure 12; and

Figure 14 is a side view of the valve of Figure 12.

Detailed Description of the Drawings

Referring now to the drawings, there is shown, generally indicated as 10, a tyre assembly embodying one aspect of the invention. The tyre assembly 10 comprises a wheel rim 12 and a tyre 14 that can be removably fitted to the wheel rim 12. The tyre assembly 10 is part of a wheel, other parts of the wheel (e.g. spokes, hub or axle) not being shown as they may vary from embodiment to embodiment and are not necessary for understanding the present invention. In preferred embodiments, the tyre assembly 10 is part of a bicycle wheel, particularly but not exclusively a wheel for an off-road or “mountain” bicycle. It will be understood that the invention is not limited to use with bicycles, and various embodiments may be suitable for use with any vehicle having pneumatic tyres, as would be apparent to a skilled person.

The wheel rim 12 is annular and substantially rigid, being made of any suitable material, typically metal, metal alloy, graphite ora composite material. The outer circumference 16 of the rim 12 is configured, conveniently by its shape, to define a respective annular seat 18 for a respective annular bead 20 of the tyre 14. In the illustrated embodiment, a respective radially projecting annular flange 22 runs around each edge of the outer circumference 16. Each bead seat 18 is defined between the inside of a respective one of the flanges 22 and the surface 24 of the outer circumference 16 that extends between the flanges 22. The region defined by surface 24 is sometimes referred to as the drop centre or well.

The tyre 14 comprises an annular tread portion 26 extending between first and second annular side walls 28, the tread portion 26 and side walls 28 defining a tyre cavity 29. Each bead 20 runs around a free end of a respective one of the side walls 28. The tyre 14 may be made from any suitable material, typically natural or synthetic rubber.

The tyre 14 can be removably fitted to the rim 12. When fitted, the beads 20 are seated in the respective seat 18 to define an enclosed space 30 between the outer circumference 16 of the rim 12 and the inside surface of the tyre 14. In preferred embodiments, the tyre assembly 10 does not include an inner tube for containing pressurised fluid, i.e. the tyre assembly 12 may be referred to as a tubeless tire assembly. As such, the tyre 14 is inflated by pumping fluid, typically air, into the enclosed space 30 via a valve 32 to create a desired fluid pressure in the enclosed space 30. Typically the tyre 14 has a rated fluid pressure, the level of which may depend on, amongst other things its size, purpose and/or the material from which it is made. The tyre assembly 10 is of a type commonly referred to as a pneumatic tyre assembly, and the tyre 14 may be referred to as a pneumatic tyre.

The tyre assembly 10 includes an annular protective tyre insert 40. As can best be seen from Figure 4, the insert 40 is in the form of a ring. In preferred embodiments, the insert 40 is (at least in its rest state) semi-rigid, i.e. sufficiently rigid to be self-supporting but not inflexible. Preferably, the insert 40 has a solid core, i.e. it is not hollow. It is further preferred that the insert 40 is not elastically stretchable.

The insert 40 may take any desired shape in transverse cross-section. For example, the transverse cross-section of the insert 40 may be circular, oval, elliptical, triangular, rectangular or polygonal in shape, and may be regular or irregular. Optionally, the insert 40 may be shaped to provide a protrusion 42 at one or both of its sides. The, or each, protrusion 42 preferably runs around the whole circumference of the insert 40, but may alternatively run around one or more parts of the circumference of the insert 40. In preferred embodiments, there is a circumferential protrusion 42 on each side of a main body 44 of the insert. The protrusions are preferably rounded in transverse cross-section. The main body 44 of the insert is preferably oval in transverse cross-section.

Advantageously, the insert 40 is formed from a compressible material. In preferred embodiments, the insert 40 is formed from a polymeric material (including polymeric blends), preferably a polymeric foam or rubber. For example foam rubber, cellular rubber, sponge rubber or expanded rubber may be used. It is particularly preferred that the insert 40 is formed from a cellular material. It is particularly preferred to use closed cell material, for example a closed cell foam or a closed cell rubber. By way of example, the insert 40 may be formed from EPDM (ethylene propylene diene monomer) foam or EPDM rubber, or from CR (chloroprene) foam or CR rubber, or Neoprene, or PU (polyurethane foam). Semi-closed cell material, for example semi-closed cell EPDM or other semiclosed cell polymeric material, may alternatively be used. Alternatively still open cell material such as open cell foam, e.g. sponge foam, or open cell rubber, e.g. sponge rubber, may be used. In any event, the compressible material from which the insert 40 is made, in combination with the ring shape of the insert 40, causes the insert 40 to contract, or shrink, at least diametrically but typically also cross-sectionally, when subjected to elevated ambient fluid pressure in comparison with its size at a normal ambient fluid pressure, e.g. ambient atmospheric pressure. The insert 40 maintains its smaller size so long as the elevated fluid pressure is maintained, and may revert to its original, or natural, size when the fluid pressure is reduced. Accordingly, the size of the annular insert 40, in particular its diameter, depends on the ambient fluid pressure to which it is subjected.

In a rest state (which may also be referred to as a natural or uncompressed state), in which the insert 40 is subject to normal atmospheric pressure and is not otherwise compressed or subjected to external forces, the insert 40 maintains its ring shape with natural, uncompressed dimensions. In conditions of elevated fluid pressure around he insert, i.e. pressure above atmospheric pressure, the insert 40 contracts, or shrinks. In particular, the diameter of the insert 40 reduces when the insert 40 is subject to elevated pressure. Hence, in a contracted state, the annular insert 40 has a diameter that is smaller than its diameter in the rest state. The cross-sectional area of the insert 40 is typically also reduced in the contracted state with respect to its size in the rest state.

The insert 40, in its rest state, is shaped and dimensioned to fit inside the tyre 14, and more particularly inside the tyre cavity 29. As such, the outer diameter of the insert 40 (in the rest state) is less than the internal diameter of the tyre 14 (as defined by the inner surface of the tread portion 26 in this example). Preferably, the insert 40 is dimensioned such that, when the tyre 14 and the insert 40 are concentric, there is an annular gap 48 between the inner surface of the tread portion of the tyre 14 and the insert 40.

The insert 40 is also shaped and dimensioned to fit loosely around the rim 12 in its rest state. As a result, when the insert 40 is located around the rim 12 in its rest state, it does not grip or otherwise fit tightly on the rim 12. To this end, the insert 40 is, in its rest state, diametrically larger than the rim 12. In particular, the insert 40 is dimensioned such that, when the rim 12 and the insert 40 are concentric, there is an annular gap 46 between the rim 12 and the insert 40. To this end, the inner diameter of the insert 40 (in the rest state) is larger than the diameter of the rim 12. In particular, the inner diameter of the insert 40 (in the rest state) is larger than at least the central portion of the rim 12 (or the drop centre 24 of the rim 12). Preferably, the inner diameter of the insert 40 (in the rest state) is larger than the widest diameter of the rim 12, which is typically determined by the flanges

22.

Similarly, the insert 40 is shaped and dimensioned in transverse cross-section to fit within the tyre cavity 29 in its rest state. To this end, the width Wof the transverse cross section of the insert 40 (in its rest state) is less than the internal width of the tyre 14 (at least with respect to the widest distance between the side walls 28). The height H of the transverse cross-section of the insert 40 (in its rest state) is less than the internal height of the tyre 14 (at least with respect to the distance between the bead end and the tread portion 26).

When the tyre assembly 10 is being assembled, the insert 40, in its rest state, may be placed inside the tyre cavity 29, and the tyre 14 can be fitted to the rim 12 in normal manner. Advantageously, because the insert 40 does not fit tightly to the rim 12 in its rest state, the presence of the insert 40 inside the tyre 14 does not interfere with fitting the tyre beads 20 to the bead seats 18. As a result, the user does not require any special tools to fit the tyre 14 to the rim 12.

Figures 2 and 3 show the tyre assembly 10 in an assembled state in which the tyre 14 is fitted to the rim 12 and the insert 40 is located within the tyre 14. In Figures 2 and 3 the tyre 14 is not inflated and so the fluid pressure in the enclosed space 30 is normal atmospheric pressure. As such, the protective insert 40 is uncompressed and in its rest state. In these circumstances, the insert 40 fits loosely within the tyre cavity 29, around the rim 12. In preferred embodiments, in addition to not gripping the rim 12, the shape and dimensions of the uncompressed insert 40 are such that the insert 40 does not press against the side walls 28 of the tyre 14, or against the tread portion 26 of the tyre 14. In typical embodiments, when the insert 40 is uncompressed, it is capable of moving within the enclosed space 30, for example being movable laterally, radially and/or rotationally within the tyre 14.

It will be understood that the dimensions of the insert 40 in its rest, or uncompressed, state depend on the dimensions of the rim 12 and the tyre 14 with which the insert 40 is intended for use. In some embodiments the insert 40 may be up to 20% larger (e.g. between 0.1% and 20% (inclusive) larger, but more typically between 0.5% and 10% (inclusive) larger) than the rim 12 diametrically in its rest state, and may contract diametrically to fit the rim 12, when compressed, by a corresponding amount.

With reference in particular to Figures 6 and 7, when the tyre 14 is inflated, the elevated fluid pressure within the enclosed space 30 compresses the protective insert 40, causing it to contract. The contraction causes the diameter of the insert to reduce. In preferred embodiments, during inflation, the insert 40 contracts, in particular diametrically, until it engages circumferentially with the rim 12. Advantageously, the insert 40 contracts to create a tight fit around the rim 14. Conveniently, the arrangement is such that the insert 40 contracts, at least diametrically, until it is prevented from doing so further by engagement with the rim 12. Accordingly, in response to inflation of the tyre 14, the insert 40 shrinks to fit the rim 12. Typically, in this contracted state, the compressed insert 40 is seated in the drop centre 24 of the rim 12. In the contracted state, the gap 46 that was between that was between the insert 40 and the outer circumference 16 of the rim 12 has been closed. The gap 48 between the insert 40 and the inner surface of the tyre 14, particularly at the tread portion 26 is still present, and is widened in comparison with the deflated tyre 14. In preferred embodiments, in the contracted state, the insert 40 engages with, and may grip, the rim 12.

In preferred embodiments the insert 40 is intended for use with a bicycle tyre assembly. The fluid pressure in a bicycle tyre depends on a number of factors including the size of the tyre and the type of cycling. Also, it may be desirable to adjust the tyre pressure to suit any one or more of the weight of the rider, weather conditions, the terrain and desired comfort. For example, such adjustments may alter the tyre pressure by up to ±20psi with respect to a maximum rated pressure. For example, a typical maximum rated tyre pressure for bicycle tyres may be 30-130psi. A typical in-use tyre pressure for a mountain bike is 20-45psi, while for a road bike a typical in-use tyre pressure is 80115psi. It is noted that these exemplary pressure values are gauge pressure valves which are relative to ambient atmospheric pressure. Normal atmospheric pressure is approximately 14.7psi in absolute terms, but corresponds to Opsi as a gauge pressure value. Therefore, in typical embodiments, the insert 40 maintains its natural (or rest) size at atmospheric pressure of approximately 14.7psi (absolute) or Opsi (gauge), and contracts in response to elevated pressure above 14.7psi (absolute) or Opsi (gauge). In typical embodiments the insert 40 may contract in response to elevated pressure of 10-30psi (gauge). By way of example, in one embodiment, the insert 40 is configured to shrink diametrically by approximately 7.5% at 30psi (gauge pressure). A decrease in cross-sectional diameter is typically also caused by the elevated pressure, which in the present example may be approximately 15% at the same elevated pressure.

It will be understood that annular inserts embodying the invention may be configured (e.g. by means of their size and/or composition) to contract at different pressures to suit the application. The characteristics (typically including density and hardness) of the material from which the insert 40 is made may be selected by balancing the requirement for shrinkage against the need to provide some resistance to compression in order to provide the desired protection to the tyre and rim, as suits the application.

In its contracted state, the shape and dimensions of the compressed insert 40 are such that a respective part of the insert 40 is located over either edge of the rim 12. In the preferred embodiment, the protrusions 42 are located over a respective edge of the rim 12. The rim edges are provided by the flanges 22 in typical embodiments. As a result, during use when the tyre 14 deforms under load, the insert 40 serves as a cushion between the deforming tyre 14 and the rim 12. As such, the insert 40 provides the tyre assembly 10 with protection against pinch punctures, as well as protecting the rim 12 itself. Further, when the compressed insert 40 is seated on the rim 12, in particular being located in the drop centre or well of the rim, it helps to keep the beads 20 in the bead seats 18, and in particular to inhibit lateral movement of the beads 20 away from the seat 18. This is advantageous, since lateral movement of the beads away from their seat (which can occur in response to lateral loads exerted on the tyre while riding) can allow fluid to escape from the tyre.

Referring now in particular to Figures 8 to 14, a preferred embodiment of valve 32 is described. The valve 32 has a valve stem 50 and a valve head 52. When both the tyre 14 and the valve 32 are fitted to the rim 12, the valve head 52 is located inside the tyre 14 and the stem 50 extends through an aperture provided in the rim 12 to expose the valve’s external fluid port 54. The valve head 52 includes the internal fluid port 56, the fluid ports 54, 56 being connected by a fluid channel 58 in the valve stem 50. The valve head 52 includes one or more fluid channel 60 that opens at a face, or a respective face, of the valve head 52 that is oblique or perpendicular to the radial direction of the rim 12, for example a face that faces laterally or tangentially with respect to the rim 12. In the preferred embodiment, the valve head 52 has a front face 64, first and second side faces 66 and first and second end faces 68. When the valve 32 is fitted to the rim 12, the front face 64 faces radially away from the rim 12, the side faces 66 face substantially laterally (i.e. substantially in a direction that is perpendicular to the radial direction and parallel with the rotational axis of the rim 12), and the end faces 68 face substantially tangentially (i.e. substantially in a direction that is perpendicular to the radial direction and in the rotational plane of the rim 12). The valve head 32 has a fluid channel 60, in the preferred form of a groove, that opens onto at least one of but preferably both of the end faces 68. In the illustrated example, the channel 60 also opens on to the front face 64, although this is optional. Alternatively, or in addition, the channel 60 may open onto one or both of the side faces 66. In any case, the opening(s) of the channel 60 provide at least part of the internal fluid port 56 of the valve 32. The channel 60 is in fluid communication with the fluid channel 58 to allow fluid, usually air, to flow between the fluid ports 54, 56.

During inflation of the tyre 14, fluid is pumped into the tyre 14 through the valve 32 and enters the enclosed space 30 via the opening(s) of the channel 60 (as illustrated by broken arrows in the drawings). As the insert 40 compresses under the fluid pressure, the insert 40 is pressed downwards onto the valve head 52. This tends to block any fluid openings provided in the front face 64 of the valve head 52. While this may not prevent further inflation of the tyre 14 (since the pressurised fluid can force its way between the valve head and the insert 40), it may hinder further inflation and may prevent, or at least hinder, deflation of the tyre 14. Advantageously, the opening(s) provided in the non-radial faces, i.e. in the end faces 66 in the illustrated embodiment, are not obscured by the compressed insert 40 and therefore allow not only inflation but also deflation of the tyre 14. The preferred valve 32 ensures a tight and sealed connection to the rim, ensuring that there is no air leakage past the rim tape.

The invention is not limited to the embodiment(s) described herein, which can be modified or varied without departing from the scope of the present invention.

Claims

1. A tyre assembly comprising:

a wheel rim;

2. The tyre assembly of claim 1, wherein said compressible material is a cellular material, preferably a closed cell material.

3. The tyre assembly of claim 1 or 2, wherein said compressible material is a polymeric material, for example a foam or rubber.

4. The tyre assembly of any preceding claim, wherein said annular insert is semi-rigid.

5. The tyre assembly of any preceding claim, wherein said annular insert has a solid core.

6. The tyre assembly of any preceding claim, wherein said annular insert is configured to contract diametrically to engage with said rim in response to inflation of said tyre.

7. The tyre assembly of any preceding claim, wherein said annular insert is configured to contract diametrically to fit tightly around said rim in response to inflation of said tyre.

8. The tyre assembly of any preceding claim, wherein in said rest state said annular insert is loosefitting around said rim.

9. The tyre assembly of any preceding claim, wherein in said rest state said annular insert is loosely located inside said tyre and around said rim.

10. The tyre assembly of any preceding claim, wherein said annular insert is dimensioned such that, when the annular insert is in its rest state, and the tyre and the insert are concentric, there is an annular gap between an inner surface of a tread portion of the tyre and the annular insert.

11. The tyre assembly of any preceding claim, wherein said annular insert is dimensioned such that, when the annular insert is in its rest state, and the rim and the insert are concentric, there is an annular gap between an inner surface of the annular insert and the rim.

12. The tyre assembly of any preceding claim, wherein, in a contracted state of the annular insert, a respective part of the insert is located over each edge of the rim.

13. The tyre assembly of any preceding claim, wherein said annular insert includes a respective lateral protrusion extending at least partly, and preferably fully, around the insert in a circumferential direction.

14. The tyre assembly of claim 13, when dependent on claim 12, wherein the respective lateral protrusion is located over the respect edge of the rim.

15. The tyre assembly of any preceding claim, further including a valve having a valve head that includes at least one fluid channel that opens at a face of the valve head that is oblique or perpendicular to the radial direction of the rim when the valve is fitted to the rim.

16. The tyre assembly of claim 15, wherein the valve head has a front face, first and second side faces, and first and second end faces, wherein, when the valve is fitted to the rim, the front face faces radially away from the rim, the side faces face substantially laterally with respect to the rim, and the end faces face substantially tangentially with respect to the rim, and wherein said at least one fluid channel opens at any one or more of said side or end faces.

17. The tyre assembly of claim 15 or 16, wherein said at least one fluid channel comprises a groove formed in the valve head, and wherein said groove preferably runs substantially perpendicular with the radial direction of the rim.

19. An annular tyre insert formed from a compressible material that causes a diametric size of said insert to change depending on ambient fluid pressure.

20. The tyre insert of claim 19, wherein said compressible material causes said annular insert to contract diametrically in response to elevation of fluid pressure around said insert.

21. The tyre insert of claim 19 or 20, wherein the compressible material causes said annular insert to contract diametrically in response to fluid pressure above atmospheric pressure.

22. The tyre insert of any one of claims 19 to 21, wherein the tyre insert is shaped and dimensioned for location inside a tyre around a wheel rim, and wherein, in a rest state, said annular insert is diametrically larger than said rim.

23. The tyre assembly of any one of claims 19 to 22, wherein said compressible material is a cellular material, preferably a closed cell material.

24. The tyre assembly of any one of claims 19 to 23, wherein said annular insert is semi-rigid.

25. The tyre assembly of any one of claims 19 to 24, wherein said annular insert has a solid core

26. A valve having a valve head that includes at least one fluid channel that opens at a face of the

5 valve head that is oblique or perpendicular to a radial direction of a wheel rim when the valve is fitted to the rim.