GB1570215A

GB1570215A - Floating caliper disc brakes

Info

Publication number: GB1570215A
Application number: GB4535776A
Authority: GB
Original assignee: Akebono Brake Industry Co Ltd
Current assignee: Akebono Brake Industry Co Ltd
Priority date: 1975-10-31
Filing date: 1976-11-01
Publication date: 1980-06-25
Also published as: FR2329900A1; DE2649843A1; DE2649843C2; FR2329900B1

Description

(54) FLOATING CALIPER DISC BRAKES (71) We, AKEBONO BRAKE INDUSTRY Co. LTD., a Japanese Company, of No. 2-3, l-chome, Koami-cho, Nihonbashi, Chuoku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a disc brake assembly of the floating caliper type.

Floating caliper disc brakes are known in which a caliper is mounted for sliding movement parallel to the disc axis and is arranged to urge two friction pads on to opposed faces of the disc. The pads are slidably mounted on a support which usually is in the form of a U-shaped bracket with the disc passing between the arms thereof. Because the distance between the pads themselves and a fixed mounting for the bracket is of necessity somewhat long, high forces are involved and the bracket has to be of considerable size and weight in order to have sufficient strength.

According to this invention, there is provided a disc brake assembly of the floating caliper type, comprising a support member for a pair of friction pads to be positioned one adjacent each face of a brake disc, a caliper for urging the friction pads into engagement with the faces of the disc, the caliper being mounted on the support member by means allowing sliding movement of the caliper parallel to the axis of the disc, and the support member including two portions the first of which extends parallel to one face of the disc on one side thereof to carry a first friction pad and the second of which extends at right-angles to the first portion and passes across the other face of the disc substantially parallel to a chord thereof to carry a second friction pad, the first portion being adapted for mounting on a fixed support, whereby the reaction torques on braking are transferred from the first and second pads directly to the first and second portions of the support member respectively.

The first and second portion of the support member may respectively be made from two independent flat plates, -attached to each other, for instanceby bolting or welding, at right angles to provide the support member.

Alternatively, the support member may be formed by suitable bending and working of a flat plate having an opening in its central region.

The means allowing sliding movement of the caliper preferably includes a main guide pin attached to one of the support member and the caliper and slidable in the other of the support member and the caliper, the main guide pin extending parallel to the axis of the disc. A sub-guide pin may also be provided which is attached to one of the support member and the caliper and slidable within the other of the caliper and support member. One of the guide pins conveniently extends through an elastomeric bush having axially-extending, circumferentially-spaced grooves, so as to reduce the drag between the pin and the push.

Conveniently, the main guide pin is associated withither slidably or in a fixed manner spaced arm forming part of the first portion or of the second portion of the support member. For the case in which the support member comprises two separate plates bolted together, a further plate may be provided between the first portion and the second portion, which further plate is also held in position by the bolts attaching together the two portions, the further plate forming an arm associated with the main guide pin.

In a preferred embodiment, the first portion defines a pair of grooves in which projections on the first friction pad can be located slidably to mount the pad for movement towards and away from the brake disc, and the second portion defines a pair of rails on which grooves on the second friction pad can be located slidably to mount the pad for movement towards and away from the brake disc. Preferably, the pair of grooves for the first friction pad is positioned nearer the axis of the disc than the pair of rails for the second friction pad. In this embodiment the two friction pad may be similar, if each pad has a pair of projections engageable with the pair of grooves on the first portion and has a pair of grooves engageable with the pair of rails of the second portion, the two pads being interchangeable.

This invention extends to the combination of a disc brake assembly as described above, a pair of friction pads slidably mounted on the support member and a rotatable brake disc arranged with the friction pads one to each face respectively of the disc.

In the arrangement of this invention the distance between the support member subjected to braking forces and the fixed mounting-for instance, a suspension part in the case of a vehicle-may be made relatively short, whereby the deformation of the support member at the time of braking may be decreased. Also, the support member may be made smaller in shape and of a simple construction.

By way of example only, seven specific embodiments of this invention will now be described, reference being made to the accompanying drawings, in which: Figure 1 is a plan view of a first embodiment of a disc brake assembly according to this invention; Figure 2 is an elevational view of the assembly of Figure 1; Figure 3 is a sectional view taken along line A-A of Figure 1; Figure 4 is a view of the clips used for fixing the friction pads in the assembly of Figure 1; Figure 5 is a plan view of a second embodiment of a disc brake assembly according to this invention; Figure 6 is an elevational view of the assembly of Figure 5; Figure 7 is a plan view of a third embodiment of a disc brake assembly according to this invention Figure 8 is an elevation view of the assembly of Figure 7; Figure 9 is an end view of the assembly of Figure 8; Figure 10 is a plan view of a support member used in a fourth embodiment of this invention; Figure 11 is an elevational view of the member of Figure 10; Figure 12 is an end view of the member of Figure 10; Figure 13 is a plan view of a fifth embodiment of a disc brake assembly according to this invention; Figure 14 is an elevational view of the assembly of Figure 13; Figure 15 is a central sectional view of the assembly of Figure 13; Figure 16 is a plan view of the support member used in the assembly of the fifth embodiment; Figure 17 is an elevational view of the support member of Figure 16; Figure 18 is a plan view of the support member and the friction pads used in a sixth embodiment of this invention; Figure 19 is an elevational view of the arrangement of Figure 18, showing a part only thereof; Figures 20 and 21 each show modified arrangements of the sixth embodiment of this invention.

Figure 22 is a plan view of a seventh embodiment of a disc brake assembly according to this invention; and Figure 23 is a sectional view taken along line B-B drawn on Figure 22.

In the following description, referring to the drawings, like parts to different embodiments, or parts taking essentially the same function, will be given the same reference characters.

Referring now to Figures 1 to 4, showing the first embodiment of disc brake assembly, there is shown a brake disc 1 which is suitably rotatably mounted but fixed axially and which for example may be attached to a road wheel of a vehicle. A fixed mounting 2-for example, a part of the suspension of a vehicle--carries a support member 3 which, when viewed end-on, is generally Tshaped. The support member 3 comprises a first flat plate 4 which is secured and a second flat plate 5 fixed to the first plate 4.

The first flat plate 4 has a recess 4a and is arranged so that it lies parallel to braked faces of the disc 1, on one side thereof, with the opening into the recess 4a being outside the periphery of the disc. The second flat plate 5 is generally C-shaped and is arranged so that the tips of its left and right arms 5b and Sc are respectively fixed to the left and right arms 4b and 4c of the first flat plate 4, the general planes of the two plates being at right angles. The central part 5d of the second plate lies on the other side of the disc 1 to the flat plate 4. Friction pads 6 and 7 are provided to engage the two faces of the disc, pad 6 being regarded as the "inner" pad when the assembly is mounted on a vehicle and pad 7 as the "outer" pad.

The inner pad 6 is supported for sliding movement parallel to the axis of the disc 1 by means of a projection 6b formed in a back-plate 6a of the pad, which projection engages a groove 4d provided in the first flat plate 4. The outer pad 7 is also supported for sliding movement parallel to the disc axis, by means of a groove 7b formed in a back-plate 7a of the pad, which groove engages a guide rail 5a provided in the second flat plate 5. A caliper 8 is arranged to exert pressure on the friction pads 6 and 7, the caliper having a hydraulicallyoperated piston 9 on one side of the disc 1 and a reacting portion 8a on the other side thereof, piston 9 and portion 8a respectively engaging pads 6 and 7. The caliper 8 is mounted on the first flat plate 4 such that it may move axially of the disc 1 by means of a main guide pin 10 and a sub-guide pin 11. One end of the main guide pin 10 is permanently pressed into a bore in the caliper 8, the end of the pin being serrated as shown, the other end of the pin 10 being a sliding fit in a bearing member 12 which is mounted on the first flat plate 4, adjacent the tip of the arm 4b. The subguide pin 11 has a threaded portion and is fixed by a nut 13 engaged thereon to the first flat plate 4 adjacent the tip of the arm 4c, the pin 11 also being slidably received in a resilient bush 14 carried by the caliper 8. The bush 14 has a portion 16 serving as a protective boot for the pin 11, whereas pin 10 is provided with a separate boot 15 to protect the other end of the pin. Pad clips 17 and 18 (Figure 4) are provided to prevent rattling of the friction pads 6 and 7 in a tangential direction with respect to the disc 1.

The operation of the above-described first embodiment of disc-brake assembly will now be described.

The friction pads 6 and 7 are respectively supported by the first and second flat plates 4 and 5 of the support member 3, and upon operation of the brake the reaction torque generated by the pads 6 and 7 is absorbed by the support member 3. Thus, the reaction torque is not transferred to the caliper 8 and so the pins 10 and 11 will not be subjected to shearing forces. The pins however support the caliper 8 such that it may move in a direction axially of the disc 1 allowing the caliper 8 to move as the brake is operated to apply equal forces to the pads 6 and 7. As will be appreciated, the guide pins 10 and 11 are respectively cantilevered from the caliper and the support member and slidably movable respectively in the bearing member 12 and the bush 14, whereby movement of the caliper relative to the support member and parallel to the disc axis is possible. The freedom of this movement reliably can be maintained, because the sliding faces of the guide pins 10 and 11 are isolated from the external atmosphere by the associated simple boot 15 or 16, thereby preventing rusting and the ingress of foreign matter.

Furthermore, in this embodiment the part of the plate 4 in which the pin 11 is located is slotted outwardly at 19 (see Figure 2), whereby when nut 13 has been loosened sufficiently, the caliper may be pivotted about the main guide pin 10, the sub-guide pin moving clear of the support member 3.

In this way the caliper 8 may be moved out of the way to allow access to the friction pads 6 and 7, for instance for replacing them. This clearly is a simple operation.

As will be appreciated the support member 3 is formed from two flat plates which is both simple to make and reliable in operation since it provides a rigid structure.

The number of parts needed in the disc brake assembly with the floating caliper is small and assembly as well as replacement of the friction pads is particularly easy.

Figures 5 and 6 show the second embodiment of disc brake assembly of this invention. A disc 101 is rotatably mounted in a suitable manner with a support member 102 mounted on a fixed part-such as a suspension part-so as to lie adjacent the braking faces of the disc 101. The support member is substantially T-shaped in end view, and comprises a generally C-shaped supporting plate 103 the arms 103a and 103b extending beyond the periphery of the disc 101. A second supporting plate 104, also generally C-shaped, is connected at right angles to plate 103 by means of bolts 105 extending through arms 103a and 103b into threaded holes 104c and 104d provided in arms 104a and 104b of plate 104, such that the central portion of plate 104 lies on the opposed side of the disc to plate 103. To accommodate the threaded holes 104c and 104d, the arms 1Q4 and 104b of plate 104 are of increased cross-sectional thickness.

Friction pads 106 and 107 are slidably supported respectively on plates 103 and 104.

Plate 104 has cranked arms (as shown in Figure 6) to provide a pair of guide rails 104e and 104f for pad 107, such that the pad wholly overlies the disc face, whereas pad 106 slides directly on the arms 103a and 103b of plate 103. A caliper 110 is mounted on plate 103 for sliding movement parallel to the disc axis, by means of a pair of guide pins 108 and 109, pressed into holes provided in arms 103a and 103b of plate 103.

The above-described construction provides a reliable disc brake assembly. The strength of the combination of the two supporting plates 103 and 104 is high, and by cranking the guide rails 104e and 104f for the friction pad 107, the two supported pads are aligned and opposed, allowing a floating caliper to be used with a single operating piston. The whole assembly protrudes only slightly beyond the periphery of the disc, allowing the arrangement to be used simply in automotive applications.

Figures 7 to 9 show a third embodiment of this invention which is generally similar to that described with reference to Figures 5 and 6. In this third embodiment, how ever, the mounting of the caliper 110 is modified, the guide pins 108 and 109 being mounted on supporting plate 104t. Plate 1041 has thickened arms 1041a and 1041-b in which the bolts 105 are received, and support lugs 1041g and 1041h extending over the periphery of the disc 101, in which pins 108 and 109 are mounted. As before, the bolts 105 fasten together plates 1041 and 1031.

In this embodiment, some considerable space is obtained between the fixed portions of the slide pins 108 and 109 and boss portions 110a and 110b of the caliper 110, in which the pins slide. Protective boots (not shown) may be provided on pins in this space to facilitate the protection of sliding portions against foreign matter. When the caliper is designed, the positions of the boss portions 1 10a and 110b may be selected more conveniently, as the pins 108 and 109 are mounted further from the piston side of the caliper.

Figures 10 to 12 show the fourth embodiment of this invention generally similar to the second and third embodiments, but the guide pins 108 and 109 are mounted on independent plates 111 disposed between supporting plates 10311 and 10411 for the friction pads. As before, bolts 105 pass through plate 10311 and are threaded in holes in plate 10411, but the independent plates 111 are sandwiched between plates 10311 and 10411 with the bolts passing through holes provided therein. Rotation of each plate 111 about its associated bolt 105 is prevented by suitable means (not shown) such as interengaging concave and convex portions on the plates 111 and 10311 and 10411.

This embodiment has further advantages over those of the third embodiment. In particular, the manufacture of the plates 10311 and 10411 becomes simpler and there is greater freedom in the positioning of pins 108 and 109, by appropriate design and selection of the independent plates 111.

Figures 13 to 17 show the fifth embodiment of this invention, again somewhat similar to the preceding embodiment. Supporting member 203 is mounted on a fixed support 202 to hold friction pads 207 and 208, one to each side of a disc 201. A caliper 204 is mounted by guide pins 205 and 206 on the supporting member 203 for movement parallel to the disc axis, and includes a cylinder 209 in which a piston 210 is mounted. Guide pins 205 and 206 for slidably mounting the caliper 204 are mounted in a first plane portion 203a of the support member 203, guide pin 205 being detachably mounted so as to assist the changing of the friction pads 207 and 208, by allowing the caliper to be pivotted about pin 206. The friction pads 207 and 208 are carried by the- support member in such a manner that the reaction torque when braking is taken by the first plane portion 203a and the second plane portion 203b, which respectively lie parallel to and at right angles to the surface af the disc 201.

In this embodiment, the support member 203 having the two plane portions 203a and 203b is formed from a single flat plate having an opening in its central region. The flat plate is suitably bent and worked to form the portions 203a and 203b at right angles, interconnected by bridge portions 203e which overlie the periphery of the disc 201 when the support member is mounted as shown in Figure 13.

As shown in Figure 17, the support 203 defines a pair of guide rails 203c for carrying friction pad 207 and another pair of guide rails 203d for the other friction pad 208. These two pairs of guide rails do not lie on the same plane, there being a difference I in their levels with rail 203c being nearer the centre of the disc. This is done for manufacturing reasons, so that the forming tool for rails 203c will not interfere with rails 203d.

The support member 203 described above may be shaped so that the bridge portion 203e may closely lie over the periphery of the disc 201, as shown in the drawings. No part of the disc brake assembly thus protrudes greatly beyond the disc 20, lending the assembly to automotive applications.

Because the support is formed from a flat plate having an opening therein, it posseses various advantages such as high strength with great reliability, and low cost and weight as compared with a support member made from two or more separate pieces.

Figures 18 to 21 show the sixth embodiment of this invention, in which the support member is made from a first flat plate 301 disposed parallel to the disc face (not shown) on one side thereof and a second flat plate 302 secured to the first flat plate by means of arms 302a and 302b extending over the disc such that the remainder of plate 302 lies at right angles to the first flat plate but on the other side of the disc. Arms 301a and 301b of the first flat plate 301 are shaped to define grooves 301c extending parallel to the disc axis and in which is supported a friction pad 303. Arms 302a and 302b of the second flat plate are shaped to form rails 302c also extending parallel to the disc axis and on which is supported a friction pad 304. The friction pads 303 and 304 are respectively provided with metal back plates 303a and 304a carrying the friction linings 303b and 304b. Each side of the back plates 303a and 304a are formed with projections 303c and 304c and in the central portion of these projections are formed grooves 303d and 304d. Thus one pad is engageable with the grooves 301c of the first flat plate 301 and the other pad is engageable with the rails 302c of the second flat plate 302.

It will be appreciated that the projections 303c of pad 303 fits within the grooves 301c of the first flat plate 301, whereas the grooves 304d of the friction pad 304 fit over the rails 302c of the second flat plate. Because both pads have projections and grooves, they are interchangeable. The reaction torque on braking is transferred from the pads to the flat plates, and the areas for transferring this torque are as follows. In the case of pad 304, and if the back plate thickness is a, the areas as shown in Figure 19-is Si 12.a and in the case of pad 303, S2 = lt + 13).a. If (ll + Ia) is twice as long as 12, although the back of back plate 303a protrudes beyond the flat plate 301 by about half the thickness of the back plate 303a the torque receiving area for both pads is approximately equal, so high surface pressures may be avoided.

To mount the caliper (not shown) for sliding movement parallel to the disc axis, holes 305 are provided in which guide pins for the caliper can be located.

Figures 20 and 21 show other modifica- tions of the arrangement of Figures 18 and 19. In these, a projection 306c or 307c and grooves 306d or 307d are provided for engagement with the flat plates 301 and 302 quite independently of each other.

In these modifications, either friction pad may be used on either side of the disc. The engagement area for transferring torque to the first flat plate 301 is related to the contacting length 14 or 15 shown in the drawings, provided this is sufficiently larger than l2 for the pad on plate 302 (which is the same as in Figures 18 and 19 and equal to the plate thickness) the area will be sufficient to ensure a satisfactory braking operation.

By having interchangeable pads the manufacturing costs and replacement pad costs may be maintained low. Figures 22 and 23 show the seventh embodiment of this invention, in which a support member 402 extends from the fixed mounting towards the rim of the disc 401 parallel to the face of the disc to define a first portion 402a, there being a second portion 402b extending at right angles to the first portion 402a and passes across the other face of the disc 401 substantially parallel to a chord thereof.

The first portion 402a of the support member 402 has a pair of guide pins 403 and 404 fixed therein, to support a caliper 405 in such a manner that it may slide freely parallel to the disc axis. The caliper 405 has boss portions 405a and 405b, through which the guide pins 403 and 404 respectively extend, boss portion 405a being provided with an elastomeric bush 406 defining a bore for pin 403. Friction pads 407 and 408 are also mounted on the support member 402.

The above structure is similar to those of the preceding embodiments, but this embodiment differs in that the elastomeric bush 406 is provided. This bush 406 is located in the boss portion 405a to define a bore 406a for pin 403, but a number of axially extending, circumferentially-spaced grooves 406b are provided around the bore 406z This arrangement is effective to decrease the sliding resistance as compared with the case in which the guide pin 403 mutually contacts the elastomer bush 406 over the whole of the internal face of the bore 406z For a case in which no grooves 406b are provided, the elastomer is apt to provide high drag on movement of the pin, especially when the pin bears heavily radially on the elastomer, in which case the drag is considered to be proportional to the contacting areas. This disadvantage is avoided by providing the grooves 406b to decrease the contacting areas, and any deformation of the bush caused by radial pressure can be absorbed by the grooves 406b, thereby reducing further the drag under radial loads.

Furthermore, in the case of the outer surface of the guide pin 403 getting rusty and thus increasing the diameter of the pin, the increase may be accommodated by deformation of the contacting parts of the bush into the grooves 406b thereby giving no significant increase in sliding friction.

WHAT W;E CLAIM is:- 1. A disc brake assembly of the floating caliper type, comprising a support member for a pair of friction pads to be positioned one adjacent each face of a brake disc, a caliper for urging the friction pads into engagement with the faces of the disc, the caliper being mounted on the support member by means allowing sliding movement of the caliper parallel to the axis of the disc, and the support member including two portions the first of which extends parallel to one face of the disc on one side thereof to carry a first friction pad and the second of which extends at right-angles to the first portion and passes across the other face of the disc substantially parallel to a chord thereof to carry a second friction pad, the first portion being adapted for mounting on a fixed support, whereby the reaction torques on braking are transferred from the first and second pads directly to the first and second portions of the support member respectively.

2. A disc brake assembly according to claim 1, wherein the first portion and the second portion of the support member are respectively made from two independent flat plates, attached to each other at right angles to provide the support member.

3. A disc brake assembly according to claim 2, wherein the two portions of the support member are bolted together.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. and the other pad is engageable with the rails 302c of the second flat plate 302. It will be appreciated that the projections 303c of pad 303 fits within the grooves 301c of the first flat plate 301, whereas the grooves 304d of the friction pad 304 fit over the rails 302c of the second flat plate. Because both pads have projections and grooves, they are interchangeable. The reaction torque on braking is transferred from the pads to the flat plates, and the areas for transferring this torque are as follows. In the case of pad 304, and if the back plate thickness is a, the areas as shown in Figure 19-is Si 12.a and in the case of pad 303, S2 = lt + 13).a. If (ll + Ia) is twice as long as 12, although the back of back plate 303a protrudes beyond the flat plate 301 by about half the thickness of the back plate 303a the torque receiving area for both pads is approximately equal, so high surface pressures may be avoided. To mount the caliper (not shown) for sliding movement parallel to the disc axis, holes 305 are provided in which guide pins for the caliper can be located. Figures 20 and 21 show other modifica- tions of the arrangement of Figures 18 and 19. In these, a projection 306c or 307c and grooves 306d or 307d are provided for engagement with the flat plates 301 and 302 quite independently of each other. In these modifications, either friction pad may be used on either side of the disc. The engagement area for transferring torque to the first flat plate 301 is related to the contacting length 14 or 15 shown in the drawings, provided this is sufficiently larger than l2 for the pad on plate 302 (which is the same as in Figures 18 and 19 and equal to the plate thickness) the area will be sufficient to ensure a satisfactory braking operation. By having interchangeable pads the manufacturing costs and replacement pad costs may be maintained low. Figures 22 and 23 show the seventh embodiment of this invention, in which a support member 402 extends from the fixed mounting towards the rim of the disc 401 parallel to the face of the disc to define a first portion 402a, there being a second portion 402b extending at right angles to the first portion 402a and passes across the other face of the disc 401 substantially parallel to a chord thereof. The first portion 402a of the support member 402 has a pair of guide pins 403 and 404 fixed therein, to support a caliper 405 in such a manner that it may slide freely parallel to the disc axis. The caliper 405 has boss portions 405a and 405b, through which the guide pins 403 and 404 respectively extend, boss portion 405a being provided with an elastomeric bush 406 defining a bore for pin 403. Friction pads 407 and 408 are also mounted on the support member 402. The above structure is similar to those of the preceding embodiments, but this embodiment differs in that the elastomeric bush 406 is provided. This bush 406 is located in the boss portion 405a to define a bore 406a for pin 403, but a number of axially extending, circumferentially-spaced grooves 406b are provided around the bore 406z This arrangement is effective to decrease the sliding resistance as compared with the case in which the guide pin 403 mutually contacts the elastomer bush 406 over the whole of the internal face of the bore 406z For a case in which no grooves 406b are provided, the elastomer is apt to provide high drag on movement of the pin, especially when the pin bears heavily radially on the elastomer, in which case the drag is considered to be proportional to the contacting areas. This disadvantage is avoided by providing the grooves 406b to decrease the contacting areas, and any deformation of the bush caused by radial pressure can be absorbed by the grooves 406b, thereby reducing further the drag under radial loads. Furthermore, in the case of the outer surface of the guide pin 403 getting rusty and thus increasing the diameter of the pin, the increase may be accommodated by deformation of the contacting parts of the bush into the grooves 406b thereby giving no significant increase in sliding friction. WHAT W;E CLAIM is:-

1. A disc brake assembly of the floating caliper type, comprising a support member for a pair of friction pads to be positioned one adjacent each face of a brake disc, a caliper for urging the friction pads into engagement with the faces of the disc, the caliper being mounted on the support member by means allowing sliding movement of the caliper parallel to the axis of the disc, and the support member including two portions the first of which extends parallel to one face of the disc on one side thereof to carry a first friction pad and the second of which extends at right-angles to the first portion and passes across the other face of the disc substantially parallel to a chord thereof to carry a second friction pad, the first portion being adapted for mounting on a fixed support, whereby the reaction torques on braking are transferred from the first and second pads directly to the first and second portions of the support member respectively.

4. A disc brake assembly according to

claim 1, wherein the first and second porticks of the support member are formed from a single flat plate having an opening in its central region, by suitable bending of the plate to provide the two portions at right-angles.

5. A disc brake assembly according to claim 4, wherein the support member defines two bridge portions connecting the first and second portions, which bridge portions extend arcuately over the rim of the brake disc.

6. A disc brake assembly according to any of the preceding claims, wherein the means allowing sliding movement of the caliper includes a main guide pin attached to one of the support member and the caliper and slidable in the other of the support member and the caliper, the main guide pin extending parallel to the axis of the disc.

7. A disc brake assembly according to claim 6, wherein the main guide pin is associated with an arm which forms a part of the second portion of the support member.

8. A disc brake assembly according to claim 6, wherein the main guide pin is associated with an arm which forms part of the second portion of the support member.

9. A disc brake assembly according to claim 3 and claim 6, wherein a further plate is provided between the first portion and the second portion, which further plate is also held in position by the bolts attaching together the two portions, the further plate forming an arm associated with the main guide pin.

10. A disc brake assembly according to any of claims 7 to 9, wherein the main guide pin is attached to the arm and is cantilevered therefrom.

11. A disc brake assembly according to any of the preceding claims, wherein the first portion defines a pair of grooves in which projections on the first friction pad can be located slidably to mount the pad for movement towards and away from the brake disc.

12. A disc brake assembly according to any of the preceding claims, wherein the second portion defines a pair of rails on which grooves on the second friction pad can be located slidably to mount the pad for movement towards and away from the brake disc.

13. A disc brake assembly according to claim 12, wherein the pair of grooves for the first friction pad is positioned nearer the axis of the disc than the pair of rails for the second friction pad.

14. A disc brake assembly according to claim 12 or claim 13, wherein a pair of similar friction pads are provided, each pad having a pair of projections engageable with the pair of grooves on the first portion and having a pair of grooves engageable with the pair of rails of the second portion, the two pads being interchangeable.

15. A disc brake assembly according to claim 14, wherein each groove of the pair thereof on each pad is provided within a face of the projections on the pads.

16. A disc brake assembly according to claim 14, wherein each groove of the pair thereof on each pad is provided remote from the projections on the pad.

17. A disc brake assembly according to claim 6, or any claim appendant thereto, wherein the means allowing sliding movement of the caliper further includes a subguide pin attached to one of the support member and the caliper and slidable in the other of the support member and caliper, the sub-guide pin extending Iparallel to the axis of the disc.

18. A disc brake assembly according to claim 17, wherein one of the guide pins is received slidably within a bore of an elasto- meric bush, the bush having a plurality of axially-extending, circumferentially-spaced grooves around the bore.

19. A disc brake assembly substantially as hereinbefore described, with reference to and as illustrated in Figures 1 to 4 or in Figures 5 and 6 or in Figures 7 to 9 or in Figures 10 to 12 or in Figures 13 to 17 or in Figures 18 and 19 or in Figure 20 or in Figure 21 or in Figures 22 and 23 of the accompanying drawings.

20. A disc brake comprising the combination of an assembly according to any of the preceding claims, a pair of friction pads slidably mounted on the support member and a rotatable brake disc arranged with the friction pads one to each face respectively of the disc.