GB2595663A

GB2595663A - Sealing arrangement for a sliding caliper disc brake

Info

Publication number: GB2595663A
Application number: GB2008207.9A
Authority: GB
Inventors: Roberts Paul; Jackson Jonathan; Dawson Andrew; Randall Alexis; Kinder Adrian
Original assignee: Mei Brakes Ltd
Current assignee: Mei Brakes Ltd
Priority date: 2020-06-01
Filing date: 2020-06-01
Publication date: 2021-12-08
Anticipated expiration: 2040-06-01
Also published as: GB2595663B; GB202008207D0

Abstract

A sliding caliper disc brake comprises a slidable guide pin 18 in a bore having an end sealed by a two-part sealing cap. The sealing cap comprises a flexible elastomeric ring section 22, and a rigid insert 24 for inserting into the elastomeric ring 22. A watertight cover provided by a skin 28 may be integrated into the elastomeric ring 22 and a rigid plastic cover may be integrated into the rigid insert 24. A ring 26 of the rigid section 24 has a ridge (36, fig 3) which corresponds with an annular recess in an inner wall of the elastomeric ring 22 that is in a same axial position as ridge (32) on an outer wall of the elastomeric ring 22. The ring 26 is slightly flexible and resilient and can flex inwards to allow the ridge 36 to pass the inner wall of the outer elastomeric ring 22 when the rigid section 24 is being inserted or removed. In position the rigid insert 24 holds the elastomeric section 22 in position, sealing the caliper bore.

Description

SEALING ARRANGEMENT FOR A SLIDING CALIPER DISC BRAKE

The present invention relates to sliding caliper disc brakes for vehicles, in particular air disc brakes for large road vehicles such as buses and trucks and trailers.

BACKGROUND TO THE INVENTION

In a sliding caliper disc brake, the brake pad on one side moves with respect to the caliper, towards the disc, when the brake is actuated. The brake pad on the other side of the disc is fixed relative to the caliper. To provide a clamping force to both sides of the disc, the whole caliper moves axially relative to the brake disc, when the brake is actuated, to bring the brake pad which is fixed to the caliper into contact with the brake disc. The whole caliper also moves axially relative to the brake disc to allow for wear of the pad and disc To allow this to happen, the caliper is typically mounted onto a brake carrier by means of two guide pins, which are bolted to the brake carrier, and which slide in bushes within bores of the caliper. The guide pin arrangement should be sealed, ideally at both ends, to protect against water and dirt ingress from the road which will cause the sliding system to seize.

The sliding system needs to be serviced from time to time. In particular the bushes are wearable parts which will require replacement during the normal lifetime of the brake. A flexible sealing boot is generally provided on the side of the bore which faces the carrier. The sealing boot may also become damaged over time and need to be replaced.

A common design for a sliding caliper brake includes a long guide pin and a short guide pin. The long guide pin slides entirely within a bore in the caliper, which is long enough to surround the guide pin over the full range of movement of the caliper due to pad and disc wear (and brake actuation). The shorter guide pin generally slides within a short through-bore in the caliper and passes all the way through the caliper and protrudes from the other side, at least when the pads and discs are new and unworn.

EP3246585 discloses a sealing arrangement for the short guide pin in such a design.

The long guide pin has generally been sealed by a simple metal press-fit cap. Because the long guide pin never protrudes out of the end of its respective bore in the caliper, a press-fit cap over the end of the bore, on the side of the caliper facing away from the carrier, provides for a simple and effective seal if fitted correctly. However, such seals are generally single-use, and if removed in order to service the bushes a brand-new sealing cap must be fitted. Furthermore, these metal press-fit caps are difficult to fit correctly without making use of specialist tools. Often, when an attempt is made to fit the cap using for example a hammer, the cap will be damaged and will need to be replaced. If a cap is fitted incorrectly and the fault is not noticed, then water may leak into the brake. This can lead to seizure of the sliding system so that the brake is not free to slide back on the off-stroke after brake application. This can result in uneven pad wear and potentially a hot running brake, which in turn could lead to nonopfimal or even dangerously poor brake performance.

Screw-in caps have been used in some designs. Screw-in caps are effective, easy to fit using standard tools, and are reusable. However, the cost of manufacture is increased. Also, if the thread in the guide pin bore is damaged, the seal may no longer be effective.

It is an object of the present invention to provide a low-cost, re-usable, and effective sealing arrangement for a caliper bore of a sliding caliper brake.

The arrangement of two guide pins, one of which remains within its respective caliper bore and one of which protrudes from the caliper bore, creates further difficulties in providing effective sealing. Although effective arrangements have been proposed, for example in EP3246585, to seal the short guide pin, the long and short guide pin arrangement creates complexity and increases the number of distinct parts making up a caliper.

It is a further object of the invention to reduce the complexity and lower the cost of a sliding caliper disc brake by having common parts for both long and short pins.

STATEMENT OF INVENTION

According to the present invention, there is provided a sliding caliper disc brake arrangement comprising: a brake carrier having at least one guide pin; a brake caliper having a through bore to receive the guide pin, the guide pin being slidable within the bore; and a two-part sealing cap for sealing the end of the caliper bore which faces away from the carrier, the two-part sealing cap comprising: an elastomeric ring section including a sealing outer surface for sealing against an inner surface of the caliper bore; and a substantially rigid removable insert section for inserting into the elastomeric ring section, for bearing against an inner surface of the elastomeric ring section and for holding the elastomeric ring section in position between the substantially rigid insert section and the inner surface of the caliper bore, at least one of the elastomeric ring section and the substantially rigid insert section including a cover section for closing the end of the caliper bore and preventing ingress of water and dirt.

The guide pin, which is normally cylindrical, may be surrounded by the caliper bore in the sense that the guide pin does not protrude from the caliper bore. Alternatively the guide pin may, at least when the pads and disc are new and unworn, protrude from the caliper bore. In this case the bore and the two-part cap will define a cavity including an extension of the bore, within which the guide pin may move.

The caliper bore is a through bore, and the two-part sealing cap closes the end of the bore on the side of the caliper which faces away from the carrier.

The removable insert section is rigid compared with the elastomeric ring section, but is preferably slightly resiliently deformable as will be described in more detail below.

The substantially rigid insert section may include a ring, the ring having axial breaks around the ring and extending at least part the way along the axial length of the ring for example to form a set of fingers. The ring (or fingers) extend into the caliper bore in use, contacting an inner surface of the elastomeric ring section.

By providing these axial breaks / slots around the ring, some resilient flexibility in the fingers is provided to facilitate easy insertion and removal of the ring.

The two-part sealing arrangement can be fitted easily by hand. By providing an elastomeric seal section, and separately a rigid retainer, the elastomeric section can be positioned by hand, without any significant pressure being applied and without any risk of damage, precisely against an inside surface of the caliper bore. The elastomeric seal section is readily flexible and can easily be manipulated into position by hand.

Once the elastomeric seal section is in the correct position, the rigid insert is pushed into place (again, typically by hand), to hold the elastomeric seal firmly in position. No special tools are required, and there is no motivation to use hammers or similar tools at the risk of damaging the components.

The elastomeric ring section may be made from a rubber compound, or from an artificial material having similar properties.

One or the other or both of the elastomeric section and the rigid section includes a cover or skin which closes the end of the caliper bore, preventing ingress of dirt and water.

Preferably, the elastomeric ring section has a ridge extending around its outer sealing surface. A corresponding annular recess may be provided around the inside surface of the caliper bore, for receiving the ridge. The ridge of the elastomeric ring, and the corresponding recess of the caliper bore, serve to locate the elastomeric ring in position prior to insertion of the rigid retainer. Once the retainer is inserted, the ridge and corresponding recess also help to hold the elastomeric ring firmly in position.

Because the elastomeric ring can be inserted before the rigid retainer, the ring is flexible and can be inserted by hand with minimal force. The ridge and corresponding recess can therefore be made fairly deep, for example about 2mm radially. In embodiments, the ridge and recess are preferably at least 1mm deep, more preferably at least 1.5mm deep, most preferably at least 2mm deep.

One or more further ridges may be provided around the outer sealing surface. The further ridges may be substantially less high, for example about 0.5mm. These ridges act as sealing beads and may assist with ensuring good grip between the elastomeric ring section and the inside surface of the caliper bore. It may be that recesses in the caliper bore are not provided to correspond with these sealing beads. Rather, the beads are designed to be compressed in use to help form a good watertight seal against the inside surface of the caliper bore.

In one embodiment, the elastomeric ring section has an inner ring section and an outer ring section. In such an embodiment, it is the outer ring section which sits against the inner surface of the caliper bore in use, and the rigid insert is bears against an inner surface of the outer elastomeric ring section. The inner ring and outer ring sections define a pocket, or U-shaped section, an entrance to the pocket facing out of the caliper bore when the elastomeric ring section is inserted into the caliper bore. This pocket is sized to receive the rigid insert. Forming the elastomeric ring section as a U-shaped profile in this way assists with providing a structure which will stay in place while the rigid part is being inserted.

Where the cover section is provided on the elastomeric ring section, the cover may extend between an outer axial extent (i.e. the end facing out of the caliper bore in use) of the inner (that is, radially inner) ring.

The substantially rigid removable insert may be made from plastic. The material may have some resilience but is substantially rigid compared with the elastomeric ring. It is convenient to form the plastic insert as a cap, and in some embodiments the cover section may be provided as part of the rigid cap, i.e. a continuous skin extending over the entrance to the caliper bore in use. However, it is most preferable to provide the watertight cover section as part of the elastomeric ring section. A cover section could still be provided as part of the rigid cap, but in this case an aperture is preferably provided through the cap. This ensures that air is not compressed between the elastomeric ring section and the substantially rigid section during fitting, which could result in forces dislodging the seal. This also prevents a vacuum from holding the cap in, making removal difficult.

A cover section on the rigid cap, with an aperture through the cover section, does not form a watertight seal -the cover section of the elastomeric ring section is relied on for sealing. However, a cover section on the rigid cap may provide useful protection for the elastomeric ring section against mechanical damage, for example caused by stones and other particles thrown up from the road while the vehicle is being driven.

The ring, or the fingers formed by a broken ring, of the rigid insert may have at least one ridge running around its outer surface. Where the insert has a ring broken into fingers the ridge may run around the ring but be broken, i.e. the breaks in the ring may extend at least as far as the ridge. A recess in the inner surface of the elastomeric ring (that is, the inner surface of the outer ring section where the elastomeric ring has inner and outer sections) may be provided corresponding with the position of the ridge on the outer surface of the rigid insert ring. Preferably, the position of the ridge on the outer surface of the rigid insert ring and the recess in the inner surface of the elastomeric ring corresponds with the axial position of the ridge on the outer surface of the elastomeric ring and corresponding recess in the inner surface of the caliper bore.

A flange or lip may extend radially outwardly, from the axially outer extent of the rigid insert ring. This serves to cover the axial outer extent of the elastomeric ring section, protecting the seal from damage. The flange is also useful when the rigid insert needs to be removed. A suitable tool, for example a flat-head screwdriver, can be inserted under the flange of the rigid insert ring to ease the rigid insert out of the caliper bore without damaging either the elastomeric ring or the rigid insert.

The caliper bore may be provided with a counterbore at the end of the bore facing away from the carrier, i.e. the diameter of the bore into which the elastomeric ring section is fitted as described above may be greater than the diameter of the caliper bore along most of its extent. This allows an end of the carrier guide pin to extend into the counterbore, and be surrounded by (but spaced from by at least a few millimetres, for example about 3.5mm) the two-part sealing cap in use. Therefore, the caliper bore can be kept as short as possible while fully enclosing the carrier guide pin in use.

In one embodiment of a brake, the carrier has two guide pins and the caliper has two corresponding bores, and both bores are sealed by similar two-part sealing caps as described above. Preferably the elastomeric ring of one of the two-part sealing caps is identical to the elastomeric ring of the other of the two-part sealing caps. Preferably the rigid insert of one of the two-part sealing caps is identical to the rigid insert of the other of the two-part sealing caps. By using common parts, the cost is reduced.

Two guide pins may be provided which are fully surrounded by their corresponding caliper bores when in use. Keeping the caliper bore as short as possible, while facilitating this, means that a compact brake can be made which will not foul against other vehicle components. A brake having two guide pins, both of which are surrounded by the caliper bore along their entire length, provides for a lower distinct part count and greater simplicity, and also avoids the problems of sealing the "short guide pin" which in prior designs typically extends out of the other side of the caliper.

The caliper bores may have a bush to allow smooth sliding (the caliper itself being typically cast iron and the bush being a wrapped cylindrical part with a smooth surface). The bush may stop short of the counterbore in the end of the caliper bore which faces away from the carrier. The bushes may be of any suitable type, including for example wrapped cylindrical parts, rubber bushes, plastic mouldings and sintered bronze.

In some embodiments, the caliper bore(s) are sufficiently long so as to surround the end of the guide pin which faces away from the carrier, in all positions of the caliper relative to the carrier.

Throughout the description, use of the words "axial" and "radial" is with reference to the axis of the guide pin and caliper bore, when all the components are assembled to seal the caliper bore The arrangement described is particularly suitable for use in an air disc brake for a heavy road vehicle, such as a bus or truck.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example only to the accompanying drawings, in which: Figure 1 is a schematic cross-section of a caliper bore, carrier guide pin and sealing cap, in a prior art disc brake; Figure 2 is a cross-section of a caliper bore, carrier guide pin and two-part sealing cap according to the present invention; Figure 3 is a magnified view of part of Figure 2; Figure 4 is a sectioned perspective view of the two-part sealing cap of Figure 2; Figure 5 is a cross-section illustrating a second embodiment of a two-part sealing cap according to the invention; Figure 6 is a cross-section illustrating a third embodiment of a two-part sealing cap according to the invention; and Figure 7 is a cross-section illustrating a fourth embodiment of a two-part sealing cap according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figure 1 shows schematically a common prior art arrangement used in sliding caliper disc brakes. A carrier guide pin 10 slides within a bore in a brake caliper. A wrapped cylindrical bush 11 is provided within the bore. The carrier guide pin 10 slides in contact with the bush 11, which in turn is fixed within the caliper bore.

A metal end cap 12 seals the end of the caliper bore which faces away from the carrier.

The metal end cap 12 provides an effective seal, but only if correctly fitted. If damaged during fitting, or if not fitted straight, the metal end cap 12 may provide an imperfect seal and allow water and dirt into the brake. This can cause corrosion and friction in the sliding system, and prevent the brake returning correctly on the off-stroke.

The metal end cap 12 needs to be removed for servicing, which typically involves replacing the bushes and the elastomeric sealing boots (not shown) on the other end of the caliper bore, i.e. on the end of the bore facing the carrier. The metal end cap 12 is a single-use component and needs to be discarded when removed and replaced with a new cap.

Figure 2 illustrates an improved sealing arrangement in accordance with the invention.

Part of the caliper body is indicated at 14. A wrapped cylindrical bush 16 is provided within a bore through the caliper 14, and a guide pin 18 slides in the bush 16. The guide pin 18 is bolted to a brake carrier which is not shown, but which would be to the left in the drawing. The head of the bolt is indicated at 20. Hence the part of the caliper bore shown is at the end of the caliper bore which faces away from the carrier.

A two-part sealing cap comprises an elastomeric ring section 22 and a comparatively rigid insert 24. The elastomeric ring section 22 has an outer surface which when fitted abuts an inner surface of a counterbore of the caliper bore. The rigid insert 24 includes a resilient ring section 26 which is inserted into the elastomeric ring section 22, so that the elastomeric ring is held between the ring section 26 of the insert and the inner surface of the counterbore of the caliper bore.

Although in this embodiment the rigid insert 24 is generally in the form of a cap, substantially covering the end of the caliper bore, the actual watertight seal is provided by skin 28, part of the elastomeric section 22. The rigid insert 24 has an aperture 30 through the cover part, so that air can pass through, avoiding building up pressure which could dislodge the elastomeric section 22 during fitting, or creating a vacuum making the rigid insert 24 difficult to remove.

The cap of the rigid insert 24 nevertheless protects the skin 28 of the elastomeric ring section 22 from mechanical damage, for example abrasion caused by dirt or stones.

Referring now to Figure 3, the elastomeric section 22 includes an outer ring section 22a and an inner ring section 22b. The outer and inner ring sections 22a, 22b are joined at an inner axial end (with reference to the caliper bore) 22c. The inner axial end 22c forms a thicker single ring section along part of the axial length of the elastomeric section 22. This helps define the shape of the elastomeric section 22 and ensure that it sits in position before the rigid insert 24 is inserted.

The outer ring 22a, inner ring 22b and inner axial end 22c together define a U-shaped pocket, with an entrance facing out of the caliper bore when the elastomeric section 22 is fitted in position in the caliper bore. The pocket is sized to receive the ring section 26 of the rigid insert.

The substantially circular skin 28 extends to fill the space inside the inner ring 22b of the elastomeric section 22.

The elastomeric section 22, including the outer and inner rings 22a, 22b and the skin 28, is preferably formed from a single piece of material.

A ridge 32 runs around the outer surface of the outer elastomeric ring 22a. The ridge corresponds with an annular recess provided in the inner wall of the caliper bore. Further, smaller, ridges 34 are provided also running around the outer surface of the outer elastomeric ring 22a. These smaller ridges 34 have no corresponding recess in the caliper bore, but provide sealing beads to improve grip and sealing between the elastomeric ring 22a and the caliper bore.

VVhere the counterbore of the caliper bore ends, a ledge 37 is formed. The axial extent of the elastomeric section 22, when correctly fitted, may be such that it sits on or very close (for example less than 1mm) to the ledge 37. This further assists with manually locating the elastomeric section 22 prior to inserting the rigid insert 24.

The ring 26 of the rigid section 24 likewise has a ridge 36 extending round it. The ridge corresponds with an annular recess in the inner wall of the outer elastomeric ring 22a, which is substantially in the same axial position as the ridge 32 on the outer wall of the outer elastomeric ring 22a. The ring 26 of the rigid section 24 is slightly flexible and resilient. The position of the ring 26 shown in Figure 3 is its "natural" / resting position but the ring 26 can flex inwards (downwards in the cross section of Figure 3) to allow the ridge 36 to pass the inner wall of the outer elastomeric ring 22a when the rigid section 24 is being inserted or removed. In position as shown in Figure 3, the rigid insert 24 serves to hold the elastomeric section 22 in position, sealing the caliper bore.

Figure 4 shows a perspective view of the elastomeric section 22 and the rigid insert 24. It will be apparent that the ring 26 of the rigid insert 24 has axial breaks at intervals, which extend just over half way along the axial (relative to the axis of the caliper bore in use) length of the rigid insert 24. Therefore the rigid insert is essentially made up of a number of resilient fingers, together forming a broken ring 26. The axial length of the breaks can be determined to tune the resilient flexibility of the fingers, to achieve the right balance between an insert 24 which is easy to insert and remove, and an insert 24 which securely and reliably holds the elastomeric section 22 in place.

It is also apparent from Figure 4 that the rigid insert forms a cap over the elastomeric section 22 in use. VVhile the cap has an aperture 30 to prevent a sealed pocket of air, and therefore does provide a watertight seal, the cap nonetheless protects the skin 28 of the elastomeric section from mechanical damage. The cap also extends outwards beyond the ring 26, to provide a flange or lip covering the outer ring 22a of the elastomeric section, preventing dirt ingress and damage.

Figure 5 shows an alternative arrangement, whereby the ridge 32' of the outer ring 22a' of the elastomeric section is provided at an inner extent along the axial length of the elastomeric section 22'. The annular recess in the caliper bore is provided in a corresponding position, as is the ridge 36' of the rigid ring 26' In the embodiment of Figure 5, the ridge 36' is at a distal end of the ring 26' of the rigid insert 24'. The flexibility of the ring 26' will allow more displacement at the distal end than at any other point, and so the rigid insert 24' will be easier to insert. Also, the sealing beads 34' in the Figure 5 embodiment do not have to pass the annular recess of the caliper counterbore as the cap is inserted or removed. The risk of damage to the sealing beads 34' in this embodiment is therefore reduced.

Figure 6 shows a further embodiment. The Figure 6 embodiment is in most respects the same as the Figure 5 embodiment, and like reference numerals are used to refer to like parts. In Figure 6, the caliper bore is not sufficiently long to surround the guide pin. In at least some states (e.g. when the brake pads and discs are new and unworn), the guide pin extends out of the end of the caliper bore, as shown in the drawing. However, the two-part cap still seals the end of the guide pin bore. The two-part cap defines a cavity part of which is in effect an extension of the caliper bore, within which the guide pin can slide. Preferably, the two-part cap never touches the guide pin, in any position of the guide pin. There is preferably clearance of at least 1mm, for example about 3-4mm.

In terms of the construction of the Figure 6 embodiment, the elastomeric ring has inner and outer rings 22a", 22b", in a similar arrangement to the Figure 5 embodiment. However, the inner ring 22h" is significantly longer than the outer ring 22a", so that when the outer ring 22a" sits in the end of the caliper counterbore, the inner ring 22a" extends out of the bore, and together with the sealing skin 28" forms a sealed cavity within which the guide pin can slide, protected from dirt and water. The rigid insert is likewise long enough to extend out of the bore, protecting both the inner ring 22h" and skin 28" of the elastomeric ring from mechanical damage.

The Figure 7 embodiment is similar, and the elastomeric ring is exactly the same as the elastomeric ring of the Figure 6 embodiment. The difference in Figure 7 is that the rigid insert only includes the resilient ring section 26-, and has no cover section to protect the elastomeric skin 28-from mechanical damage.

To install the two-part sealing arrangement, firstly the elastomeric section 22, 22' is manually fitted in the correct position in the caliper bore. This is easy to do because the elastomeric section 22, 22' is flexible, and the ridge 32 fits in the annular recess to locate the elastomeric section 22, 22' and lightly hold it in place. The ledge 37 where the counterbore of the caliper bore ends also assists with correct location.

Mien the elastomeric section 22, 22' is in the correct place, the rigid insert 24, 24' is pushed into place. Again, this is easy to do by hand. 1A/hen in place, the elastomeric section 22, 22' and rigid insert 24, 24' are held securely, and provide a reliable seal against dirt and water ingress. The parts are unlikely to be damaged while fitting.

To remove the two-part cap, a screwdriver or similar tool can be inserted underneath the lip/flange of the rigid insert 24, 24', and used to gently prise the rigid insert 24, 24' out of the caliper bore. Once the rigid insert 24, 24' is removed, the elastomeric section 22, 22' can easily be removed by hand from the caliper bore. Removal can also be easily undertaken without damaging the parts of the two-part cap, so the same two-part cap can be used to re-seal the caliper bore once replacement of the wear parts (typically the bushes and sealing boots) is complete.

The embodiments described above are provided by way of example only, and various changes and modifications will be apparent to persons skilled in the art without departing from the scope of the present invention as defined by the appended claims.

Claims

CLAIMS1. A sliding caliper disc brake arrangement comprising: a brake carrier having a guide pin; a brake caliper having a bore to receive the guide pin, the guide pin being slidable within the bore; and a two-part sealing cap for sealing the end of the caliper bore which faces away from the carrier, the two-part sealing cap comprising: an elastomeric ring section including a sealing outer surface for sealing against an inner surface of the caliper bore; and a substantially rigid removable insert section for inserting into the elastomeric ring section, for bearing against an inner surface of the elastomeric ring section and for holding the elastomeric ring section in position between the substantially rigid insert section and the inner surface of the caliper bore, at least one of the elastomeric ring section and the substantially rigid insert section including a cover section for closing the end of the caliper bore and preventing ingress of water and dirt.
2. A sliding caliper disc brake arrangement as claimed in claim 1, in which the elastomeric ring section includes a cover for providing a watertight seal over the end of the caliper bore in use.
3. A sliding caliper disc brake arrangement as claimed in claim 2, in which the rigid removable insert incorporates a cover for protecting the cover of the elastomeric ring section from mechanical damage.
4. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, in which the substantially rigid insert section includes a ring, the ring extending into the caliper bore in use, and a surface of the ring contacting an inner surface of the elastomeric ring section.
5. A sliding caliper disc brake arrangement as claimed in claim 4, in which the ring has axial breaks around the ring and extending at least part of the way along the axial length of the ring, to form a plurality of fingers.
6. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, in which the elastomeric ring section has a ridge extending around its outer sealing surface.
7. A sliding caliper disc brake arrangement as claimed in claim 6, in which an annular recess is provided around the inside surface of the caliper bore, for receiving the ridge of the elastomeric ring.
8. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, in which sealing beads are provided around the outer surface of the elastomeric ring.
9. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, in which the elastomeric ring section has an outer ring section and an inner ring section, the outer ring being in contact with the inner surface of the caliper bore when fitted.
10. A sliding caliper disc brake arrangement as claimed in claim 9, in which the outer and inner ring sections are joined together and define a U-shaped pocket, facing out of the caliper bore when the elastomeric ring section is inserted into the caliper bore.
11. A sliding caliper disc brake arrangement as claimed in claim 9 or claim 10, in which a watertight cover is provided as part of the elastomeric ring section, the cover extending between an outer axial extent of the inner ring.
12. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, in which the rigid insert is made from plastic.
13. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, in which the rigid insert is formed substantially as a cap, having a cover section
14. A sliding caliper disc brake arrangement as claimed in claim 13, in which an aperture is provided through the cover section.
15. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, the rigid insert including a flange or lip for covering the axial outer extent of the elastomeric ring section in use.
16. A sliding caliper disc brake arrangement as claimed in claim 4 or claim 5, in which the ring of the rigid insert has a ridge running around its outer surface.
17. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, in which a counterbore is provided in the caliper bore, at the end of the bore facing away from the carrier
18. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, in which a bush is provided within the caliper bore, the guide pin sliding within the bush in use.
19. A sliding caliper disc brake arrangement as claimed in any of the preceding claims, further including: a second guide pin fixed to the brake carrier; a second through bore in the brake caliper for receiving the second guide pin, the second guide pin being slidable within the second bore; and a second two-part sealing cap for sealing the end of the second caliper bore which faces away from the carrier, the second two-part sealing cap comprising: an elastomeric ring section including a sealing outer surface for sealing against the inner surface of the second caliper bore; and a substantially rigid removable insert section for inserting into the elastomeric ring section, for bearing against an inner surface of the elastomeric ring section and for holding the elastomeric ring section in position between the substantially rigid insert section and the inner surface of the second caliper bore.