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Installation of Rear Axle and Suspension

Module by: Andrew R. Barron. E-mail the author

For the Series 4 Lotus Seven the ends of the Ford Escort live axle were located by leading (lower) and trailing (upper) radius arms of the Watts linkage type, while the location of axle was achieved with an axle-locating link attached to the left hand side lower radius arm. The lower radius arms were mounted on big rubber bushes to compensate for the conflicted geometry as a result of bumps that is inherent on this geometry. TABLE lists a summary of the nut and bolts used in the rear suspension of the Seven S4.

Table 1: List of nut and bolts used for the rear suspension of the Lotus Seven S4.
Application Size (thread x length)
Lower radius arm to bushing 7/16” x 3”
Lower radius arm to axle 1/2” x 5”
Axle locating link to bushing 7/16” x 3”
Axle locating link to axle 1/2” x 5”
Axle locating link to center chassis mounting 1/2” x 5”
Upper radius arm to chassis 1/2” x 4” (per side)
Upper radius arm to axle 1/2” x 23/4” (per side)
Shock (damper) to axle 1/2” x 23/4” (per side)
Shock (damper) to chassis 1/2” x 3” with rounded nose (per side)

Upper radius arms

Two rubber type Y9 bushes are inserted into the axle end of each the upper radius arms (i.e., two for each side). The axle end of the upper radius arm is then pushed into locating ears on the upper side of the rear axle (Figure 1). With fresh bushings this is a tight fit, and silicone or Teflon grease is helpful in positioning the radius arms to allow the bolt to be inserted through the ears and the bushings (Figure 2). A nyloc nut is used to hold the upper trailing arm to the rear axle.

Figure 1: The upper radius links.
Figure 1 (Picture 1.jpg)
Figure 2: Right hand upper radius arm bolted to the axle.
Figure 2 (Picture 2.jpg)

The rear axle is carefully jacked up to position so that the upper radius arms can be bolted to the rear chassis using a 4” long ½” bolt (Figure 3 and Figure 4). It is worth noting that the bolt for attaching the upper trailing arm to the rear chassis is also used as a chassis-to-body mount.

Figure 3: Right hand upper radius arm bolted to the axle bolted to the rear chassis attachment point.
Figure 3 (Picture 3.jpg)
Figure 4: Axle raised into place to allow the attachment to the rear chassis.
Figure 4 (Picture 4.jpg)

Lower radius arm

The right hand lower radius arm (Figure 5B) is attached to the chassis via a type 6000 bush (Figure 6). The bushing is bolted to the chassis from the outside with the larger rubber portion facing towards the center of the chassis ((Reference)). The axle end of the lower radius arm requires two type Y9 rubber bushings. The lower radius arm is bolted to the lower fixtures in the axle using a bolt and associated nyloc nut (Figure 8). Washings are used either side of the bushings. The axle will need to be jacked up to an appropriate level in order for the radius arm to be attached to the axle.

Figure 5: The axle locating link (A) and lower radius arm (B).
Figure 5 (Picture 5.jpg)
Figure 6: An example of the type 6000 bushing used for the outer chassis mounts to the lower radius arm and the axle locating link on the Seven S4.
Figure 6 (Picture 6.jpg)
Figure 7: The right hand side type 6000 bushing in place in the chassis.
Figure 7 (bigrubberon.jpg)
Figure 8: Lower radius arm bolted to the lower attachment point on the axle.
Figure 8 (Picture 7.jpg)

Axle locating link

The axle locating link (Figure 5A) is bolted to the central chassis mount using a 5” long ½” bolt with associated nyloc nut (Figure 9). Two Y9 bushes are located into the chassis mount with appropriate washers. The left hand outer chassis attachment and the axle location for the axle locating link are bolted to the chassis in the same manner as the right hand side lower radius arm (Figure 10).

Figure 9: The axle locating link bolted to the chassis mounting.
Figure 9 (Picture 8.jpg)
Figure 10: View of the axle after attachment via the axle locating link, lower radius arm, and the upper radius arm.
Figure 10 (Picture 9.jpg)

Spring/damper unit

The upper of the rear spring/damper units are attached to the chassis using a bolt that also holds the roll bar in. The tapered end of each bolt (Figure 11) fits in a hole in the sidewall of the roll bar (Figure 12 and Figure 13).

Figure 11: The bolts used for the rear shocks that also hold the roll bar in place showing the rounded ends.
Figure 11 (Picture 10.jpg)
Figure 12: Schematic showing the location of the rear upper spring/shock unit mounting combination with the roll bar retention bolt (Figure 11).
Figure 12 (Picture 11.jpg)
Figure 13: Bolts used for the rear shocks located in position showing the position into which the damper (shock) is attached.
Figure 13 (Picture 37.jpg)

New Spax dampers (Model G655) were purchased from Redline Components, Ltd. As purchased the dampers (shocks) appear to have excess rubber around the hole associated for the bolt. In order to fit them into both the chassis and the axle it is necessary to remove the excess rubber with a scalpel. Using the tapered bolt the spring/damper units are bolted to the chassis first (Figure 14). After the axle is jacked into position it is relatively easy to push the lower end of the spring/damper unit into the locating ears on the front side of the axle (Figure 15). Once the axle is fully attached the jack can be removed (Figure 16).

Figure 14: View of spring/damper unit after bolting to chassis.
Figure 14 (Picture 42.jpg)
Figure 15: View of the left hand rear suspension showing the attachment of the upper radius arm and spring/damper unit.
Figure 15 (Picture 15.jpg)
Figure 16: View of installed spring/damper unit and lower and upper radius arms.
Figure 16 (Picture 16.jpg)

The Spax dampers (shocks) have an adjustment knob at the axle end (Figure 17). This allows for the adjustment of bump and rebound. It is a choice of whether this is positioned towards the front or rear. If it is positioned towards the front of the car, it is easier to reach. However, from experience with a Series 3 Seven, it is often easier to reach when located at the rear if adjustment is needed while the wheels are on: this is personal bias.

Figure 17: View of the rear spring/damper in place showing the bump/rebound adjustment.
Figure 17 (Picture 17.jpg)

Drums and final installation

Additional views of the installed rear axle are shown in Figure 18 and Figure 19.

Figure 18: Installed axle after removal of the supporting jack.
Figure 18 (Picture 18.jpg)
Figure 19: Installed axle.
Figure 19 (Picture 57.jpg)

Ordinarily, at this point it is appropriate to install the rear brake shoes and the associated hardware. In the present case given the timetable for the restoration the drums were bolted back into location (Figure 20 and Figure 21). This will allow the wheels to be attached.

Figure 20: Right hand rear suspension after installation of the drum, showing the attachment of the upper radius arm, lower radius arm, and spring/damper unit.
Figure 20 (Picture 20.jpg)
Figure 21: The right hub bolted in place with two lug nuts for reference.
Figure 21 (Picture 21.jpg)

Resources

  • Redline Components, Ltd. Timber Hall, 19 Timber Lane, Caterham, Surrey, CR3 6LZ, UK. Tel: +44 (0)1883 346515. www.redlinecomponents.co.uk.
  • Spax Performance, Ltd. Spax House, Murdock Road, Bicester, Oxfordshire, OX26 4PL, UK. Te: +44 (0)1869 244771. www.spax.co.uk.

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