The long threaded rod (in this case with one ³/₄” nut welded to the end) is slid into the chassis from the rear (Figure 1). Copper anti-seize (Permatex^®) is wiped into the holes in the chassis to prevent corrosion and seizing. Once the rod is through (Figure 2), the rear half of the upper wishbone is positioned and the rod pushed through the bushing (Figure 3).

Figure 1: Long threaded rod inserted via the inside of the chassis.

Figure 2: View of long threaded rod pushed through the chassis showing the copper anti-seize.

Figure 3: Rear upper wishbone in place.

Once the rear upper wishbone positioned, the spring/damper (shock absorber) is squeezed between the chassis and the rear upper wishbone. This may be very difficult since it is a very tight fit and will often require hitting the damper unit with a rubber mallet in order to obtain the correct position. In the present case a completely new spring/damper unit was sourced from Redline Components (Caterham, UK), see Figure 4. This includes a SPX PSX (G866) shock with an adjustable spring height and single adjustable damper setting. Once the damper is attached (Figure 5), the threaded rod is then pushed through the damper and out of the front of the chassis and the upper front wishbone is attached (Figure 6).

Figure 4: The new Spax damper/spring unit

Figure 5: New Spax damper/spring unit in place.

Figure 6: Upper front wishbone in place.

During powder coating of the chassis, the pins onto which the lower wishbone halves were to be slid onto were powder coated. In order to get the lower wishbones in place, this powder coat must be removed. This is most readily accomplished by carefully scrapping the majority of the material of with a razor blade and finally sanding to the bare metal. Once the excess powder coat is removed the lower wishbone halves may be slid onto the threaded pins on the chassis (Figure 7), and secured with a nyloc nut using a ³/₄” wrench. The damper is then bolted to the lower wishbones (Figure 8).

Figure 7: Attachment of rear lower wishbone, prior to putting on the retaining nyloc nut.

Figure 8: Attachment of the damper (shock) to the lower wishbones.

The ball joints are sources from a Triumph Spitfire MkIV (Moss Motors, Goleta, CA) and it is positioned between the two upper wishbones (Figure 9). The bolts were lubricated with copper anti-seize and left finger tight until the rest of the suspension was assembled.

Figure 9: View of the front left upper ball joint in place.

Once the ball joint is secure, the vertical link is bolted in place (Figure 10). The final torque will be set once the car is on the ground and the alignment is done. It is also important to ensure that the correct hand of vertical link is used. The thread on the lower of the upright is handed (left or right) depending on the trunnion used.

Figure 10: View of the vertical link attached to the ball joint.

The trunnion (from the old French “trognon” meaning trunk) allows the front hubs to rotate with the steering. The ones used on the Seven S4 are sourced from the Triumph Spitfire and Herald. They are machined from brass and are prone to failure of not greased properly. Figure 11 shows a parts diagram for the Triumph trunnion, while the various components are shown in Figure 12.

Figure 11: Schematic of the trunnion assembly showing the trunnion (A), inner water shield (B), nylon bushing (C), rectangular cross-section rubber seal (D), outer water shield (E), and distance tube (F). Adapted from Moss Motors (www.mossmotors.com).

Figure 12: The various components of the trunnion set (A – E) along with one of the original trunnions: (A) trunnion, (B) inner water shield, (C) nylon bushing, (D) rubber seal, (E), outer water shield, and (F) distance tube.

It is easiest to assemble the trunnion in stages:

The assembled trunnion is shown in Figure 13.

Figure 13: The assembled trunnion.

Prior to screwing the assembled trunnion onto the vertical link, it is necessary to slip the rubber oil seal into place (Figure 14). The trunnion is then screwed onto the vertical link (Figure 15) and once in position it is worth lubricating it at this time. It should be noted that in the present case the bleed nipple ordinarily used has been replaced with a simple bolt (Figure 14); however, this will still enable the trunnion to be lubricated. The recommended lubricant is gear oil (such as Castrol EP 80). The trunnion is then bolted to the lower wishbones (Figure 16) with a liberal application of copper anti-seize.

Figure 14: The rubber oil seal located on the bottom of the vertical link prior to screwing on the trunnion.

Figure 15: The trunnion in place on the upright and aligned correctly for attachment to the lower wishbones.

Figure 16: The front upright attached to the upper wishbones via the ball joint and the lower wishbones via the trunnion.

It is important to note that the brake caliper bracket, steering arm, and the dust shield are all “handed”. The ones for this car do not have any markings, but it is easy to work out which set is for which side by initially looking at the sizes of the holes in the bracket and the dust shield. Figure 17 shows the dust shield and caliper bracket after mounting and the difference in bolts can be clearly seen. The brake caliper and dust shield are positioned so the caliper is trailing (i.e., it is behind the axle, see Figure 17). The upper (smaller) bolts, pass through the dust shield and the caliper bracket and screw into the threads in the vertical link (Figure 18). The rear of the lower bolts passes through the dust shield, caliper bracket, and vertical link and screws into the rear of the steering arm. The front of the lower bolts passes through the dust shield, caliper bracket, vertical link, and the steering arm and is retained by a nyloc nut (Figure 19). The handed nature of the steering arm results in its being curved “up” towards the front.

Figure 17: Teflon coated dust shield in place showing the handed nature of the upright and dust shield by the difference between upper and lower pairs of bolts.

Figure 18: Front upright components: vertical links (A), left hand brake caliper bracket (B), and right hand steering arm (C).

Figure 19: View of the front suspension showing the steering arm (A) and the brake caliper bracket (B). Notice that the bolts for the brake caliper are in place.

Once the brake caliper bracket, steering arm, and the dust shield are fitted the entire front suspension can be tightened and vertical and rotation of the upright tested (Figure 20).

Figure 20: A view of the front suspension after fitting and tightening.