Mk III-T Suspension

Front Suspension

The principle of the suspension system was to maximize link lengths, minimize unsprung weight and camber change due to suspension travel. It was decided to adopt a monoshock approach, to eliminate the weight of one coilover unit. Thought was initially given to including some form of lateral chassis roll compliance, but it was concluded that since early Van Diemen FF cars and F Atlantic cars had been successful without it, the car would be completed in the simplest form, with option to re-address the central rocker for possible lateral compliance at a later date.

Closeup of Front Suspension

Upper arms are 6061-T6 alloy tubing, swaged and tapped for 3/8” rod ends. Lower arms are 4130 Chrome-Moly tubing, welded with 4130 heat-treatable rod and then heat treated to RC30 condition, then Zinc Chromated. Lower ball joint is ½” high strength rod end.

All assembly bolts are in double shear, and are rolled-thread, alloy steel tubular racing bolts.

Steering Rack with Titanium Extensions

Steering rack is a lightweight aluminum unit from Midget racing; it was too short as shipped, so extensions were fabricated from Mil Spec CP Titanium bar, moving the pivots outboard to be colinear with inboard suspension pickups to eliminate bump steer.

Milling Front Uprights from Billet

Front uprights were milled from 7075-T6 billet, an aircraft alloy chosen for its extreme strength and ease of machining. Bearing bores were machined to shrink-fit wheel bearings from Fiat X 1/9, to center wheel loads within the upright rather than on a cantilevered spindle.

Finished Upright with Stub Axle Installed

Front Brakes

Front brake rotors are drilled Speedway units, floating on aluminum hats using shoulder bolts to allow .060” of lateral float. This significantly reduces brake pedal travel and allows a firmer pedal. Calipers are Wilwood Dynalite two-piston units, using either Hawk or Performance Friction pads.

Front Suspension and Monoshock installation

With the front suspension links in place, the central pivot and suspension pushrods are seen, with an assembly strut in place of the Koni coilover to be installed later. Note suspension loads are taken directly into main structure of the chassis.

Rear Suspension

Rear Suspension Upright and Links

The rear hub carrier is fabricated from 1025 mild steel (actually sections of rectangular tubing), MIG welded. The bearing bore is the original factory steel bore, machined from the hub carrier of a Subaru Justy AWD rear drive. Justy stub axle and half shafts were also used, shortened and/or lengthened as required. The LeGrand cast magnesium sprocket carrier is also visible.

Rear Stub Axle and Half Shaft

Completed stub axle and half shaft in place, and suspension links installed. Note upper links are Aluminum tubing, lower lateral link is 4130 steel as in front suspension, with Aluminum toe link. All standard Subaru bearings and CV joints are used, allowing easy replacement with available parts.

Rear Suspension and Drive Carrier Complete

The finished rear suspension and drive carrier. The drive unit uses a VW Microbus stub axle and bearings, therefore no differential. Final drive sprocket is drilled from a blank aluminum sprocket, and the rear brake is a drilled Speedway 10.5” drilled steel rotor. The rear caliper is identical with the front calipers, a Wilwood Dynalite two-piston aluminum unit.

At this point, the suspension is complete, and can be removed from the chassis so that chassis assembly and sidepod fabrication can be completed.