The present invention relates to a brake system, a method of using a brake system, and a control system for a brake system. The present invention also relates to a kit and method for modifying a brake system. Preferred embodiments of the present invention are directed to brake systems for vehicles.

Brake systems for vehicles typically comprise a brake rotor fixed to the wheel of the vehicle. The brake rotor (which may be a disc or drum) rotates with the wheel when the vehicle is moving. With disc brakes, a pair of brake pads is typically positioned either side of the brake rotor, and the brake pads are typically brought into firm contact with the brake rotor by brake callipers. With drum brakes, brake pads are typically positioned on the inside of the brake drum and are forced outwards into firm contact with the brake drum.

Brake pads are typically fixed to a static part of the vehicle, and do not rotate with the wheel when the vehicle is moving. When the brake is activated, the brake pad is pressed firmly against the brake rotor, and friction between the static brake pad and rotating rotor causes the speed of rotation of the rotor, and therefore the speed of rotation of the wheel, to slow. This in turn slows the vehicle.

When the brake is not being activated, brake pads are usually positioned in close proximity to the brake rotor so that the distance that the brake pad needs to travel in order to firmly contact the brake rotor is small and so that the activation time for the brake is short. This is particularly the case with hydraulically actuated brakes, in which a piston that is provided at the brake pedal of the vehicle to actuate the brake is in hydraulic communication with a piston that is provided at the brake pad to move the pad into contact with the rotor. The brake pedal piston has a smaller diameter than the brake pad piston, such that a larger movement/lower force provided at the brake pedal to activate the brake is converted into a much smaller movement but a much larger force at the brake pad to move the pad. Thus, with hydraulically actuated brakes, the distance between the brake pad and brake rotor is typically necessarily small so that an appropriate amount of force can be applied by the brake pad.

A small distance between a brake pad and brake rotor can also reduce the amount of debris that can accumulate between the brake pad and brake rotor, and can keep the brake pad dry by reducing the amount of water ingress.

In some arrangements, brake pads may even be positioned in light contact with the brake rotor even when the brake is not being activated so as to minimise the distance and time to activate the brake.

However, a problem with these arrangements exists in that intermittent or constant contact between the brake pad and brake rotor when the brake is not being activated generates an undesired braking force that the vehicle has to overcome. This reduces the power and efficiency of the vehicle, and leads to higher fuel consumption. The intermittent or constant contact between the pads and rotor also causes wear on the brake pads and rotors, which can shorten the lifetime of the brake pads and rotors and can produce polluting brake pad dust.

The present invention seeks to provide brake systems that address the aforementioned problems.

According to an aspect of the present invention there is provided a brake system comprising:

a brake pad having a braking surface; and

a pressurised fluid supply in fluid communication with the braking surface of the brake pad;

wherein the system is configured such that fluid from the pressurised fluid supply is provided to the braking surface of the brake pad under non-braking conditions.

Advantageously, by providing fluid from a pressurised fluid supply to the braking surface of the brake pad, the brake pad may be forced away from the surface of any adjacent brake rotor under non-braking conditions. The fluid may also act as a lubricant between the brake pad and any adjacent rotor under non-braking conditions. This can remove or reduce the amount of frictional contact between the pads and the rotor under non-braking conditions, which in turn can increase the power and efficiency of the vehicle, and lead to lower fuel consumption. The reduced amount of frictional contact can also decrease the amount of brake pad and brake rotor wear, leading to reduced maintenance costs for replacement brake pads.

The present invention is further advantageous in that the fluid supply may cool the braking surface of the brake pad. This may reduce the incidence of brake fade, which occurs when brake pads become too hot. The fluid may also remove debris and/or water from the braking surfaces of the brake pad and rotor.

The present invention is further advantageous in that any noise generated by contact between the brake pad and an adjacent brake rotor may be reduced or avoided.

The present invention may also provide a substantially fail-safe system, in that any failure in the pressurised fluid supply may result in a brake system that operates in a

substantially conventional manner.

The brake system preferably comprises a disc brake. In these embodiments, the brake system preferably comprises a pair of opposed brake pads, preferably joined by callipers.

However, in other embodiments the brake system may comprise a single brake pad and/or may comprise a drum brake.

The brake system preferably comprises a brake rotor positioned adjacent to the braking surface of the brake pad. The fluid from the pressurised fluid supply preferably provides a gap between the brake rotor and the braking surface of the brake pad when provided to the braking surface under non-braking conditions. As will be appreciated, the "braking surface" referred to herein is the surface of the brake that contacts (or is intended to contact) an adjacent brake rotor when the brake is activated. The braking surface is therefore a surface of the brake pad which faces (or is intended to face) an adjacent brake rotor in use. The braking surface may be referred to as a "friction surface" of the brake pad. The brake pad and brake rotor will define opposed surfaces, the friction surface of the brake pad being the surface that contacts (or is intended to contact) the surface of an adjacent brake rotor in use.

The brake pad can take any desired or suitable form. For example, the brake pad may comprise a friction material (e.g. a ceramic, semi-metallic, metallic or carbon fibre material) on a support structure. In embodiments therefore the brake pad may comprise a support structure and a friction material thereon. In these embodiments the friction material defines the braking surface (rotor facing surface) and may define an opposite support structure facing surface. The friction material may be a body of friction material. The friction material may be a single (i.e. only one) layer of material, or may comprise a plurality of layers of one or more materials.

In one set of embodiments, the brake pad (or each brake pad) preferably has one or more openings in its braking surface for providing the fluid to the braking surface of the brake pad, with the pressurised fluid supply preferably being in fluid communication with the braking surface of the brake pad via the one or more openings.

The one or more openings are preferably positioned such that the brake pad does not tip or tilt when fluid is supplied to the surface of the brake pad. As will be appreciated, any inadvertent tipping or tilting of the brake pad may cause a portion of the braking surface to contact an adjacent brake rotor when the fluid is supplied to the braking surface. The one or more openings therefore preferably include one or more openings positioned substantially in the centre of the braking surface of the brake pad. The one or more openings is preferably a single (i.e. only one) opening, wherein the single opening is positioned substantially in the centre of the braking surface of the brake pad. However, in other embodiments the one or more openings may comprise a plurality of openings, wherein the plurality of openings are preferably concentrated substantially in the centre of the braking surface of the brake pad and/or are evenly distributed across the central portion of the braking surface of the brake pad, or are evenly distributed across all of the braking surface of the brake pad (so as to balance out the reactive forces provided by the fluid as the fluid exists the openings). The one or more openings are also preferably positioned such that fluid can be supplied to substantially all of the braking surface of the brake pad.

The size and/or number of openings will depend on the size and type of brake system and/or brake pad. Generally, a larger brake pad and/or more resistive brake system mechanism (e.g. callipers) will require a larger opening and/or more openings. The one or more openings may be any desired or suitable shape in cross-section. This refers to a cross-section taken in a plane through and parallel to the braking surface. For example, the or each opening may be circular, square, oval, racetrack shaped or oblong, or may be any other regular or irregular shape. The or each opening may be in the form of a slot. In a particular preferred embodiment, the or each opening is a racetrack shaped slot.

In any of the embodiments, the or each opening is preferably elongated and oriented such that (the longest dimension of) the or each opening runs substantially parallel to the longest dimension of the brake pad. These embodiments are particularly advantageous in that the fluid is effectively and evenly distributed to the majority of the surface of the brake pad (which is preferably also elongated). This can, for example, prevent or reduce the likelihood of the brake pad tipping or tilting. The use of an elongated slot also allows fluid to be distributed (e.g. from a smaller (circular) passage or tube) over a larger area. This means that, for a given fluid pressure, the force that is exerted by the fluid on an adjacent rotor, so as to separate the brake pad from the rotor, may be greater.

The length of the or each opening (the longest dimension of the or each opening) can be any desired or suitable length depending, for example, on the size and type of brake system or brake pad. However, the length of the or each opening is preferably less than 99% of the brake pad's length, more preferably less than 75% of the brake pad's length, and more preferably less than 50% of the brake pad's length. The length of the or each opening is preferably more than 1 % of the brake pad's length, more preferably more than 5% of the brake pad's length, and more preferably more than 10% of the brake pad's length. The length of the or each opening may be between 2 mm and 50 mm.

The width of the or each opening (the shortest dimension of the or each opening) can be any desired or suitable width again depending, for example, on the size and type of brake system/pad. However, the width of the or each opening is preferably less than 99% of the brake pad's width, more preferably less than 75% of the brake pad's width, and more preferably less than 50% of the brake pad's width. The width of the or each opening is preferably more than 1 % of the brake pad's width, more preferably more than 5% of the brake pad's width, and more preferably more than 10% of the brake pad's width. The width of the or each opening may be between 1 mm and 10 mm.

The depth of the or each opening is preferably the same as the thickness of the friction material of the brake pad. These embodiments are particularly advantageous in that the brake pad can wear down, but the opening will remain of substantially the same geometry. However, in other embodiments, each opening may be less than the depth of the friction material or may extend into the brake pad's support structure. The or each opening may be an opening which extends all the way through the friction material from one side of the friction material (e.g. the braking surface side) to another side (e.g. other than the braking surface side).

In embodiments, the or each opening is an opening over and above any pores inherent in the material (e.g. friction material) defining the braking surface.

In an alternative set of embodiments, the brake pad (or each brake pad) preferably comprises a porous structure in its braking surface for providing the fluid to the braking surface of the brake pad, with the pressurised fluid supply preferably being in fluid communication with the braking surface of the brake pad via the porous structure. The porous structure may be provided by a suitable porous material.

The porous structure is preferably positioned such that fluid can be supplied to substantially all of the braking surface of the brake pad via the porous structure. For example, the majority or all of the brake pad surface may be porous.

The majority or all of at least a friction material of the brake pad (i.e. not just the surface region) may also be porous. These embodiments are particularly advantageous in that the brake pad can wear down, but porous structure will remain on the surface of the brake pad. The porous structure may be provided by using porous friction material.

The porosity of the porous structure will depend on the size and type of brake system and/or brake pad. Generally, a larger brake pad and/or more resistive brake system mechanism (e.g. callipers) will require a porous structure having greater porosity (e.g. a larger region of porous structure on the surface of the brake pad and/or a more open porous structure).

It is envisaged that the braking surface may comprise one or more openings and a porous structure in the braking surface. For example, the braking surface may be provided by a porous structure having one or more openings therethrough.

In accordance with any of the embodiments of the invention, the one or more openings or porous structure may be in fluid communication with a passage or passages in the brake pad, the passage or passages being in fluid communication with the pressurised fluid supply. The fluid is preferably provided to the one or more openings or porous structure or passage or passages via a tube or tubes, preferably having a simple geometry (e.g. a circular cross- section).

The pressurised fluid supply is preferably capable of supplying pressurised fluid at a pressure that is sufficient to separate the braking surface of the brake pad from the brake rotor under non-braking conditions, i.e. provide a gap therebetween under non-braking conditions. The pressure may also or instead be insufficient to separate the braking surface of the brake pad from the brake rotor under braking conditions.

The distance of separation or gap between the brake pad and brake rotor provided by embodiments of the present invention need only be enough so that the surface of the brake pad does not contact an adjacent brake rotor. The separation is preferably of the order of 1 to 100 microns, preferably of the order of 10 microns. The gap is preferably provided across

substantially the entire surface of the brake pad.

As will be appreciated, the capabilities of the pressurised fluid supply will depend on the type and size of the brake system, the number and size of openings in the surface of the brake pad, the porosity of the brake pad, and/or the number of brake pads that are supplied with pressurised fluid. However, the pressurised fluid supply is preferably configured to supply pressurised fluid at between 0.5 kPa and 700 kPa, more preferably between 0.5 kPa and 200 kPa, even more preferably between 0.5 kPa and 50 kPa, and most preferably between 0.5 kPa and 40kPa.

The pressurised fluid supply can be powered in any desired or suitable way. However, the pressurised fluid supply is preferably powered either directly or indirectly by an engine of the vehicle (an engine that drives the wheels of the vehicle). For example, the pressurised fluid supply may be powered by (directly coupled to) an alternator shaft of an engine of the vehicle or may be powered by (directly coupled to) a drive train of an engine. Alternatively, the pressurised fluid supply may be powered by electrical power generated by an engine of the vehicle, for example the 12V DC or 24V DC power supply provided to or by the cigarette lighter of a vehicle. These embodiments are particularly advantageous in that a dedicated supply of power (e.g. a battery or generator) is not needed in or for the braking system.

The pressurised fluid supply preferably comprises a pump capable of producing the necessary pressure. Generally, a larger brake pad and/or more resistive brake mechanism (e.g. callipers) will require a pressurised fluid supply that is capable of supplying fluid at a higher pressure.

As will be appreciated, the system is configured to provide fluid from the pressurised fluid supply to the braking surface of the brake pad at least under non-braking conditions. This is preferably achieved by a system control means. It will be appreciated that any of the steps involved in providing fluid from the pressurised fluid supply to the braking surface may be carried out by the system control means of the system. Thus, references such as "the system being configured such that" may be interchanged with "the system comprising system control means being configured such that".

In preferred embodiments, the system (or system control means) is preferably configured to provide fluid from the pressurised fluid supply to the braking surface of the brake pad only under non-braking conditions. Thus, the system (or system control means) may be configured to activate the pressurised fluid supply only under non-braking conditions and/or deactivate the pressurised fluid supply under braking conditions.

The activation/deactivation may be achieved by any desired or suitable means. For example, the power provided to the pressurised fluid supply may be applied or increased to activate the pressurised fluid supply and/or the power provided to the pressurised fluid supply may be reduced or removed to deactivate the pressurised fluid supply. A system control means may be arranged to activate/deactivate the pressurised fluid supply in any of these ways.

Similarly, the brake system may also or instead comprise a pressurised fluid supply valve in fluid communication between the pressurised fluid supply and the braking surface of the brake pad. The system (or system control means) is preferably configured such that the pressurised fluid valve is opened under non-braking conditions so as to fluidly connect the pressurised fluid supply to the braking surface of the brake pad and/or is preferably configured such that the pressurised fluid valve is closed under braking conditions so as to isolate the braking surface of the brake pad from the pressurised fluid supply.

However, the system (or system control means) may provide fluid from the pressurised fluid supply to the braking surface of the brake pad under braking conditions as well as non- braking conditions. In these arrangements, the brake system of the present invention is preferably arranged so as to not reduce the braking efficiency (or so as to only insignificantly reduce the braking efficiency) of the vehicle when the pressurised fluid is supplied to the braking surface of the brake pad.

In some embodiments, a pressure release valve may be provided in fluid communication with the pressurised fluid supply. The pressure release valve is preferably configured such that, when the brake is activated and the flow of fluid to the brake surface of the brake system is reduced by the reduced gap between the brake pad and an adjacent brake rotor, the resultant build up in pressure of the pressurised fluid from the pressurised fluid supply is relieved by the pressure release valve. This can prevent damaging the brake system and can reduce the amount of force required to activate the brake (i.e. the amount of force required to bring the brake pad into contact with the brake rotor).

In preferred embodiments, the braking efficiency of the brake system is also or instead passively or actively improved. For example, the brake system preferably comprises a fluid removal means in fluid communication with the braking surface of the brake pad, the system (or system control means) being configured to operate the fluid removal means so as to allow the removal of fluid from the braking surface of the brake pad under braking conditions (and preferably only under braking conditions).

Advantageously, by passively or actively removing fluid from the braking surface of the brake pad, the brake pad can be brought towards any adjacent brake rotor using a reduced amount of force or with the assistance of negative pressure. This can reduce the activation distance and time for the brake system under braking conditions.

These arrangements are believed to be new and advantageous in their own right, and not merely in the context of the above described aspects and embodiments. Thus, according to another aspect of the present invention there is provided a brake system comprising:

a brake pad having a braking surface; and

a fluid removal means in fluid communication with the braking surface of the brake pad; wherein the system is configured such that the fluid removal means allows the removal of fluid from the braking surface of the brake pad under braking conditions.

This aspect of the present invention may comprise any or all of the preferred or optional features discussed herein as appropriate. Furthermore, as will be appreciated, the features of this aspect of the present invention and its embodiments (for example, the brake pad, system control means, etc.) may correspond to (may be) the features already discussed above.

In one set of embodiments, the brake pad preferably has one or more openings in its braking surface for removal of the fluid from the braking surface of the brake pad, with the fluid removal means preferably being in fluid communication with the braking surface of the brake pad via the one or more openings. The one or more openings preferably correspond to (are) the one or more openings already discussed above.

In an alternative set of embodiments, the brake pad preferably comprises a porous structure in its braking surface for removal of the fluid from the braking surface of the brake pad, with the fluid removal means preferably being in fluid communication with the braking surface of the brake pad via the porous structure. The porous structure preferably corresponds to (is) the porous structure already discussed above.

The fluid removal means preferably comprises a fluid removal valve in fluid

communication with the braking surface of the brake pad. The system (or system control means) is preferably configured to open the fluid removal valve so as to vent the fluid to atmosphere under braking conditions and/or close the fluid removal valve under non-braking conditions. Alternatively, the fluid removal means may comprise a fluid suction device.

In some embodiments, the fluid removal means comprises both a fluid removal valve and a fluid suction device, the fluid removal valve being in fluid communication between the fluid suction device and the braking surface of the brake pad. The system (or system control means) is preferably configured to open the fluid removal valve under braking conditions so as to vent the fluid to the fluid suction device and/or close the fluid removal valve under non-braking conditions.

The system (or system control means) is preferably configured to activate the fluid suction device under braking conditions and/or deactivate the fluid suction device under non- braking conditions. The activation/deactivation may be achieved by any desired or suitable means. For example, the power provided to the fluid suction device may be applied or increased to activate the fluid suction device and/or the power provided to the fluid suction device may be reduced or removed to deactivate the fluid suction device. The fluid suction device may comprise any desired or suitable device. However, the fluid suction device is preferably a vacuum or the aforementioned pressurised fluid supply (pump) operated in reverse or connected in reverse.

The pressurised fluid supply may be operated in reverse by the input to the pressurised fluid supply/fluid suction device (that once took in fluid) becoming the output of the pressurised fluid supply/fluid suction device (that now sends out fluid). Similarly, the output of the

pressurised fluid supply/fluid suction device (that once sent out fluid) can become the input to the pressurised fluid supply/fluid suction device (that takes in fluid). In this embodiment, the pressurised fluid supply/fluid suction device may have a first input/output and a second input/output. When acting as a pressurised fluid supply, the first input/output takes in fluid from the surrounding atmosphere and the second input/output provides fluid to the braking surface. When acting as a fluid suction device, the second input/out takes in fluid from the braking surface and the first input/output vents the fluid to atmosphere.

However, in a particularly preferred embodiment, the pressurised fluid supply operates in the same direction but is connected in reverse. In this embodiment, the pressurised fluid supply/fluid suction device has a (permanent) input for receiving fluid and a (permanent) output for providing fluid. When acting as a pressurised fluid supply, the input is placed in fluid communication with the surrounding atmosphere (e.g. by a first valve) and the output is placed in fluid communication with the braking surface (e.g. by a second valve). When acting as a fluid suction device, the input is placed in fluid communication with the braking surface (e.g. by the first valve) and the output is placed in fluid communication with the surrounding atmosphere (e.g. by the second valve).

These arrangements are particularly advantageous in that a single device can act both as a pressurised fluid supply and as a fluid suction device.

It is not necessary for the fluid removal means to be operated all the time under braking conditions, and it may be desirable to operate the fluid removal means only for a predetermined amount of time for each given braking operation so as to reduce power consumption. In these embodiments, the fluid removal means is preferably operated for between 0.5 to 5 seconds for or during a given braking operation.

The "braking conditions" and/or "braking operation" referred to above can be defined in any desired or suitable way. However, the braking conditions and/or braking operation preferably comprises the brake being activated, for example via a brake pedal or lever of the vehicle, and/or an accelerator or throttle of the vehicle not (or no longer) being activated, and/or a cruise control system for the vehicle being deactivated.

Similarly, the "non-braking conditions" referred to above can be defined in any desired or suitable way. However, the non-braking conditions preferably comprises the brake being deactivated, for example a brake pedal or lever of the vehicle not being in use, and/or an accelerator or throttle of the vehicle being activated, and/or a cruise control system for the vehicle being activated.

The system (or system control means) may comprise means for detecting braking conditions and/or a braking operation and/or non-braking conditions. In embodiments, the brake system preferably comprises a sensor arrangement (e.g. in communication with the system control means) for detecting when a brake pedal and/or an accelerator or throttle and/or a cruise control system is being activated.

The "fluid" referred to above can take any desired or suitable form. However, the fluid is preferably a gas, for example an inert gas or air. The use of air is particularly advantageous in that a dedicated supply of gas (e.g. a gas cylinder) is not needed in or for the braking system.

As discussed above, the system may be monitored and/or controlled by system control means. The system control means may have any desired or suitable form. The system control means may be mechanical, electronic, or may be a combination thereof. For example, the system may comprise one or more processors (e.g. for monitoring/controlling the braking system), sensors (e.g. for detecting whether or not a braking condition exists, for detecting pressurised fluid pressure etc.), valve actuators (e.g. for the pressurised fluid supply valve and/or fluid removal valve), voltage/current supplies (e.g. for the pressurised fluid supply and/or fluid suction device). The system control means may be part of a control system for a vehicle. The system control means may comprise any one or ones of the means listed above.

According to another aspect of the present invention there is provided a vehicle comprising the brake system described herein. This aspect of the present invention may comprise any or all of the preferred or optional features discussed herein as appropriate.

The vehicle may be a road or motor vehicle (such as bicycle, an automobile (car, van, etc.), motorcycle, quad bike, truck or bus), may be a rail vehicle (such as a tram or train), or may be an aircraft (having, for example, a landing gear comprising the brake system). The vehicle may be any one or ones of the vehicles listed above. The vehicle may have one or more brake pads (e.g. for some or all of the wheels of the vehicle), with one or more or each of those brake pads having pressurised fluid supplied to its surface in the manner described herein.

According to another aspect of the present invention there is provided a method using a brake system having a brake pad (preferably the brake system described herein), comprising: providing pressurised fluid to the braking surface of the brake pad under non-braking conditions.

According to another aspect of the present invention there is provided a method of using a brake system having a brake pad (preferably the brake system described herein), comprising: removing fluid from the braking surface of the brake pad under braking conditions.

These aspects of the present invention may comprise the provision or use of any one or more of, or all of, the preferred or optional features discussed herein as appropriate. According to another aspect of the present invention there is provided a control system for a brake system (preferably the brake system described herein) and/or for a vehicle, the control system being configured and/or arranged to implement any of one or more of, or all of, the methods described herein.

According to another aspect of the present invention there is provided a computer readable medium comprising software which, when run on a control system for a brake system (preferably for the brake system described herein) and/or for a vehicle, implements any one or more of, or all of, the methods described herein. The computer readable medium may be a physical, tangible, or non-transitory medium, such as a diskette, CD ROM, ROM, RAM, flash memory or hard disk.

As will be appreciated the features of the brake system described above may be retrofitted to an existing conventional brake system.

Thus, according to another aspect of the present invention there is provided a kit for modifying a brake system having a brake pad, the kit comprising:

a pressurised fluid supply for placing in fluid communication with the braking surface of the brake pad; and

system control means configured to operate the pressurised fluid supply so as to provide fluid to the braking surface of the brake pad under non-braking conditions.

According to another aspect of the present invention there is provided a kit for modifying a brake system having a brake pad, the kit comprising:

a fluid removal means for placing in fluid communication with the braking surface of the brake pad; and

system control means configured to operate the fluid removal means so as to allow the removal of fluid from the braking surface of the brake pad under braking conditions.

These aspects of the present invention may comprise any one or more of, or all of, the preferred or optional features discussed herein as appropriate.

According to another aspect of the present invention there is provided a method of modifying a brake system having a brake pad, the method comprising:

providing a pressurised fluid supply in fluid communication with the braking surface of the brake pad; and

providing a system control means configured to operate the pressurised fluid supply so as to provide fluid to the braking surface of the brake pad under non-braking conditions.

According to another aspect of the present invention there is provided a method of modifying a brake system having a brake pad, the method comprising:

providing a fluid removal means in fluid communication with the braking surface of the brake pad; and providing a system control means configured to operate the fluid removal means so as to allow the removal of fluid from the braking surface of the brake pad under braking conditions.

These aspects of the present invention may comprise the use or provision of any one or more of, or all of, the preferred or optional features discussed herein as appropriate.

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures in which:

Figure 1 is a cross sectional view of a brake system according to an embodiment of the present invention;

Figure 2 is a brake pad according to an embodiment of the present invention.

Figure 1 is a cross sectional view of one embodiment of a brake system 10 for a motor vehicle. The brake system comprises a wheel hub 12 (shown in part) and a brake rotor 14 (brake disc) rotationally fixed to the wheel hub 12 by a fixing 16 such as a bolt. The wheel hub 12 and brake rotor 14 rotate about a centreline 18 when the vehicle is moving.

The brake system 10 further comprises a pair of brake pads 20 adjacent to the brake rotor 14. The brake pads 20 each comprise a friction material on a support structure (not shown). The brake pads 20 each have a braking surface 24 of the friction material that faces the brake rotor 14.

The brake pads are joined to one another by brake callipers (not shown), and the brake callipers are fixed to a static (non-rotating) part of the vehicle. The braking surfaces 24 (and therefore the friction material) of the brake pads 20 can be forced into firm contact with the brake rotor 14 using the brake callipers. The brake callipers are controlled by the brake pedal of the vehicle.

The brake pads 20 each have an opening 22 for providing pressurised fluid (e.g. air) at a pressure P to the braking surface 24 of the brake pad 20 that is adjacent the brake rotor 14. The pressurised fluid is provided to the openings 22 in the braking surface 24 of the brake pad 20 from a pump (not shown) via tubes 26. The fluid that is provided to the braking surface 24 of the brake pad 20 is allowed to escape from the brake system by venting to the surrounding atmosphere in the gap between the brake pad 20 and the brake rotor 14.

The operation of the pump is controlled by a system control means (not shown). The system control means may be in communication with a sensor that detects the operation of the brake pedal and/or the accelerator/throttle of the vehicle so to determine whether or not braking conditions exist.

Under non-braking conditions (e.g. when the brake pedal is not activated and/or the accelerator/throttle is activated), the system control means allows pressurised fluid to be provided from the pump to the braking surfaces 24 of the brake pads 20 via the tubes 26. This may be achieved, for example, by switching the pump on and/or by opening a supply valve (not shown) that is in fluid communication between the pump and the braking surface 24. When the pressurised fluid is provided to the braking surface 24 of the brake pads 20, the fluid pushes the brake pads 20 away from the brake rotor 14 with a force F _A . The force F _A works against the force F _B of the callipers in their non-braking state. As will be appreciated, F _A may vary with the distance D that exists between the brake pads 20 and the brake rotor 14. An increase in the distance D between the brake pads 20 and the brake rotor 14 may decrease the force F _A . Conversely, a decrease in the distance D between the brake pads 20 and the brake rotor 14 may increase the force F _A . The force F _B may effectively remain the same, but may vary with the distance D (e.g. an increase in D may lead to an increase in F _B and vice versa).

The pressure P of the fluid is selected and provided such that, when F _A is equal to F _B , the brake pads 20 are positioned and maintained at a suitable distance D away from the brake rotor 14. The distance D need only be enough to prevent the brake pad 20 from contacting the brake rotor 14 (e.g. 10 microns). This prevents or reduces the frictional contact between the brake pad 20 and brake rotor 14, increasing the power and efficiency of the vehicle and decreasing brake pad wear.

Under braking conditions (e.g. when the brake pedal is activated and/or the

accelerator/throttle is not (or no longer) activated), the system control means prevents pressurised fluid from being provided to the braking surfaces 24 of the brake pads 20. This may be achieved, for example, by switching the pump off and/or by closing a valve that is in fluid communication between the pump and the brake pad braking surface 24 so as to cut-off the fluid supply to the braking surface. This brings the brake pad 20 into contact (or closer contact) with the brake rotor 14, and reduces the braking activation distance and time.

Also under braking conditions, or for a predetermined period of time after a braking operation occurs (e.g. for 1 second), the control system may actively or passively allow fluid to be removed from braking surfaces 24 of the brake pads 20. This may be achieved, for example, by a fluid removal means. For example, the fluid may be removed by switching on a vacuum (not shown) that is in fluid communication with the openings 22 of the brake pads 20, by opening a valve (not shown) in fluid communication with the braking surface 24 that vents to the surrounding atmosphere, or by operating or connecting the aforementioned pump in reverse. The removal of fluid brings the brake pad 20 into closer contact with the brake rotor 14, and reduces the braking activation distance and time.

In one arrangement, the aforementioned pump has an input that draws fluid in, and an output that provides pressurised fluid. Under non-braking conditions, the input is fluidly connected to the surrounding atmosphere, and the output is fluidly connected to the openings 22 in the brake pad 20. Under braking conditions, the output is fluidly connected to the surrounding atmosphere, and the input is fluidly connected to the openings 22 in the brake pad 20. Thus, the same pump can be used both as a pressurised fluid supply and a fluid removal (suction) device. As will be appreciated the features of the brake system 10 can be retrofitted to an existing brake system. For example, in order to provide the broader embodiments of the brake system 10, openings 20 may be provided (e.g. drilled) though existing brake pads 20 and a tube 26 may be provided in fluid communication with the openings. A suitable pump may be provided and connected to the tube 26. A suitable system control means may then be provided to control the operation of the brake system 10 in the manner discussed above.

Figure 2 shows a pair of brake pads 20 according to one embodiment of the present invention. The brake pads 20 each have a braking surface 24 with an opening 22 in that surface. The openings 22 can be fluidly connected with a tube 26 (see Fig. 1 ). The opening 22 in this particular example is a racetrack slot having a length 'b' of 21 mm and a width 'a' of 1 1 mm. Such embodiments are particularly advantageous in that the fluid is centrally, effectively and evenly distributed by the slot to the majority of the surface 24 of the brake pad 20. This can prevent the brake pad 20 from tipping and contacting the adjacent brake rotor 14 when the fluid is supplied to the surface of the brake pad 20.

Although preferred embodiments of the present invention have been described, it will be apparent to the skilled person that various features of those embodiments can be altered, removed or substituted without departing from the scope of the invention as defined by the appended claims.