GB2164458A - Tracking adjustment apparatus - Google Patents

Abstract

Apparatus for enabling toe-in and track adjustments on a road vehicle comprises a frame (16) which is placed around the vehicle, the frame including bars (18) extending longitudinally of the vehicle on opposite sides thereof, and gauging devices (24), one for each road wheel (12), which cooperate between the said bars and the vehicle wheels to enable movement of the frame into a position, defined by the readings of the respective gauging devices (24), in which the median line between the bars corresponds to the true longitudinal centre line of the vehicle. The bars (18) can then be used as a reference for toe-in and track adjustments. <IMAGE>

Description

SPECIFICATION Vehicle track and toe-in adjustment This invention relates generally to the field of vehicle track and toe-in adjustment, and in particular to apparatus which provides a reference enabling these adjustments to be made.

Motor vehicles having front and rear road axles are usually provided with means for adjusting the toe-in of at least the front wheels.

Increasingly, cars are also provided with means for adjusting the toe-in of the rear wheels, whilst competitive racing cars are also provided with means for track adjustment.

Toe-in adjustment per se is readily carried out by means of a sighting test using various known devices, but even if the toe-in is correctly set as between the wheel pair, it is not necessarily the case that the toe-in of each of the wheels is individually correct with respect to the longitudinal centre line of the vehicle.

This is not important as far as the steerable front wheels are concerned, because symmetry is an automatic consequence of steering the vehicle. However, this is not the case where the rear wheels are concerned.

Nevertheless, correct tracking of the rear wheels is important for good road behaviour, especially in high performance cars, and is an essential adjustment for racing cars.

In the last-mentioned case, wheel tracking adjustments are currently very time-consuming and problematical, and often an approximately correct setting is only obtained by trial and error.

The major problem lying behind wheel toe-in and track adjustments is that of establishing the true longitudinal centre line of the vehicle, as defined by the four road wheels. If this true centre line can be accurately defined, toein and track adjustments can be relatively simply made with high accuracy.

It is an object of this invention, therefore, to provide apparatus which enables precise toe-in and track adjustments to be carried out in a simple manner by providing a reference which in effect defines the true longitudinal centre line of the vehicle.

According to the invention, there is provided apparatus for enabling toe-in and track adjustments on a road vehicle, comprising a frame for surrounding the vehicle, which frame includes two bars held in fixed parallel relationship and extending longitudinally of the vehicle on opposite sides thereof, and four similar gauging devices for cooperating between the said bars and the vehicle wheels, each gauging device including a graduated scale and a reference point cooperating with the scale for reading of the latter, at least one of said scale and said reference point being movable relative to the other responsively to lateral movement of the bars and alteration of the degree of parallelism between the bars relative to the longitudinal centre line of the vehicle.

In use, the frame is shifted to alter the lateral position and orientation of the parallel bars so that the graduated scales read equally at the two front wheels (when nominally straight) and likewise at the two rear wheels.

It is then known that the two parallel bars lie parallel to and equidistant from the true longitudinal centre line of the vehicle, whereby accurate toe-in and track adjustments, both front and rear, can be made in a simple manner on the basis of measurements taken relative to the parallel bars.

In a preferred embodiment, the road axles are extended by means of spindles fitted to the wheel-centres. A rectangular frame is laid on the spindles to surround the vehicle. The parallel bars carry wedge shaped plates bearing graduated scales along their inclined inner edges and the spindles carry stops at positions inboard of the graduated plates, for cooperation with the inclined inner edges of said plates. The scales are read at reference points defined by the stops, and when the two front readings are equal and the two rear readings are equal, the bars at opposite sides of the frame lie parallel to and equidistant from the true longitudinal centre line of the vehicle. The frame is preferably lockable in the longitudinal direction to either the front or the rear spindles, preferably the latter, to enable the lateral and angular adjustment of the frame to be made easier.

One possible alternative arrangement has gauging devices each in the form of a graduated rod slidable through a support on the relevant parallel bar in a direction perpendicular to the latter, the rod having an abutment at its inner end for cooperation with the wheel rim (not the tyre), the wheel nuts or the wheel hub. In this case the rod supports constitute the reference points for reading of the graduated rods. Other possible arrangements can include a movable scale or reference point which is attached to the wheel, preferably at the wheel centre.

One practical embodiment of apparatus in accordance with the invention is diagrammatically illustrated in the accompanying drawings, in which: Figure 1 shows the complete apparatus in position at a vehicle; and Figure 2 shows a pair of gauging devices in enlargement.

In Figure 1, the reference 10 denotes a vehicle, more especially a racing car. It has front and rear road wheels 12.

The apparatus of this embodiment of the invention includes spindles 14 which are attached to the road wheel hubs as extensions of the road wheel axles. A rectangular frame 16 is laid on the spindles; this frame includes side bars 18 held in parallelism by crossmembers 20. Pinhole adjusters 22 enable the width of the frame to be altered to suit the vehicle width.

Four gauging devices, generally referenced 24, are carried by the parallel bars 18, one device for each wheel. These devices 24 are adjustable along the bars 18 to suit the spacing between the front and rear wheel axles, the means of adjustment being such that it can readily be ensured that the gauging devices of each of the front and rear pairs thereof are always correspondingly positioned in the longitudinal direction.

Each device 24 includes a wedge-shaped plate 26, with an inclined inner edge 28. A stop 30 is axially keyed to the end of each wheel spindle 14, but is rotatable thereon to enable exposure of a reference mark 32 thereon regardless of the angular position of fixing of the spindle to the wheel hub.

The reference mark 32 cooperates with a graduated scale marked on the inclined edge 28 of the plate 26. Thus, referring to Figure 2, the gauging devices 24 for one pair of road wheels (front or rear) are illustrated. The graduated scale on each plate 26 is referenced 34, and the stops 30 with reference marks 32 thereon, mounted on the wheels or wheel hubs as by the spindles referred to above, are also shown.

As illustrated, the frame 16 has been adjusted, by movement on the wheel spindles 14 which support it, so that the parallel bars 18 lie parallel to and equidistant from the vehicle centre line, at least as far as the illustrated pair of road wheels is concerned. Thus, both graduated scales give an equal reading at the reference marks of the stops. Lack of such parallelism and equidistance would be seen as unequal readings between the two scales, and it can readily be appreciated that it is advantageous to mark the scales numeri caliy, because if initiaily unequal readings of, for example, 13 and 17 are initially obtained, then it is known that strict parallelism will be achieved with readings of 15, as illustrated.

The frame 16 is adjusted so that equal readings are obtained both at the front and rear wheel axes, and it is then known that the sides 18 of the frame are accurately aligned parallel to and equidistant from the vehicle centre line 40. The scale readings will, of course, not necessarily be numerically the same at the rear as at the front, since the respective wheel spacings will commonly be different.

In order to facilitate the accurate setting of the frame 16, it is preferably locked to the rear spindles 14 against longitudinal movement, as by means of locking pins or clips, while the frame is being laterally and angularly adjusted.

Subsequent wheel tracking and toe-in adjustments are effected on the basis of measurements between each wheel and the adjacent parallel bar.

It will be appreciated that the above-described and illustrated arrangement is by way of example only and that various modifications, especially in respect of the nature of the gauging devices, are possible within the scope of the invention hereinbefore defined.

Claims (11)

1. Apparatus for enabling toe-in and track adjustments on a road vehicle, comprising a frame for surrounding the vehicle, which frame includes two bars held in fixed parallel relationship and extending longiiudinally of the vehicle on opposite sides thereof, and four similar gauging devices for cooperating between the said bars and the vehicle wheels, each gauging device including a graduated scale and a reference point cooperating with the scale for reading of the latter, at least one of said scale and said reference point being movable relative to the other responsively to lateral movement of the bars and alteration of the degree of parallelism between the bars relative to the longitudinal centre line of the vehicle.

2. Apparatus according to claim 1, including spindles for attaching to the wheel centres to extend the road axles and provide a support for the frame.

3. Apparatus according to claim 2, wherein the parallel bars carry the parts bearing the scales of the respective gauging devices and the spindles carry parts bearing the reference points of said respective gauging devices.

4. Apparatus according to claim 3, wherein the said parts carrying the gauging devices are wedge shaped plates each bearing its scale along its inboard edge inclined to the longitudinal axis of the vehicle.

5. Apparatus according to claim 4, wherein the said parts carrying the reference points comprise stops carried, preferably rotatably carried, by the spindles, inboard of the wedge shaped plates.

6. Apparatus according to claim 4 or claim 5, wherein the wedge shaped plates are adjustable as a rear pair and/or front pair thereof for longitudinal spacing of said pairs.

7. Apparatus according to claim 2 or any claim appendant thereto, including means for locking the frame against longitudinal movement to either the front or preferably the rear pair of spindles whilst enabling lateral movement of the bars and/or alteration of the degree of parallelism thereof.

8. A method of establishing the true longitudinal centre line of a road vehicle to enable toe-in and track adjustments, according to which a frame including two bars extending longitudinally of the vehicle is placed around the vehicle generally at the level of the road wheels, and by means of respective gauging devices cooperating between said bars and the vehicle wheels the frame is adjusted for respective readings at each gauging device which define a frame position in which the median line between the longitudinally extending bars corresponds to the true longitudinal centre line of the vehicle.

9. A method of effecting toe-in and track adjustments on a road vehicle, comprising the method of claim 8 and the further step of effecting toe-in and track adjustments relative to the longitudinal bars of the frame in the said defined position thereof.

10. Apparatus for enabling toe-in and track adjustments on a road vehicle substantially as hereinbefore described with reference to the accompanying drawings.

11. A method of enabling toe-in and track adjustments on a road vehicle substantially as hereinbefore described.