Theme : Suspension – When Independence Goes Wrong

Defying convention and chiselling away at costs can be a recipe for disaster, as one manufacturer who ought to have known better found out.

Cast your eyes over this ‘platform’. If you’re keen on guessing games, you would take in the V-engine perched over the front wheel centreline, front struts, complex looking independent rear suspension, and all round disc brakes, and conclude that it was probably ‘80s or ‘90s, most likely from the upper end of a European or Japanese manufacturer’s range.
In which case you could scarcely be more wrong. The chassis belongs to a British Ford, introduced in 1966, and costing less than £1000 in its basic form. The Zephyr/Zodiac Mk.IV was the first mass-produced British Ford car to feature independent rear suspension. The trouble is, it wasn’t much good.

Superficially, there is a lot of ingenuity in the rear suspension design. It is also surprisingly extravagant, for a company so notoriously dedicated to cost-cutting. The suspension arms are alloy castings, and the coil springs and telescopic shock absorbers are mounted separately, even though concentric mounting would have saved a few shillings.

The semi-trailing arms are large and wide-based, and the twin cross-members picking up the nose of the torque-tube and the back of the differential are well thought out, allowing the whole assembly to function as a virtual sub-frame, with the concomitant benefits to the assembly process and suppression of noise, vibration, and harshness.

However, penny-pinching was the downfall of the Mk.IV’s rear IRS. The illustration below shows an oddly familiar component where the inner semi-trailing arm bushes are fixed either side of the differential housing.

It is, no more, and no less, than a swinging shackle, of the type invariably found at one end of a longitudinal leaf-spring set-up. It is there because parsimonious Ford thought that they could save money by doing without fitting drive shafts with sliding splines, or plunging CV joints, instead going for fixed length shafts and simple universal joints. The cockamamy shackle arrangement was there to take up the movement as the wheels bumped and rebounded.

Ford seem to have made a virtue of their unusual solution. Autocar 22 April 1966 reported: “It is designed to give controlled camber and toe-in angle changes to the wheels to compensate for the weight distribution differences between the driver-only and fully-laden conditions.”

Except that it didn’t. The geometric conflicts of the driveshaft and hub resulted in unwelcome and sudden changes in camber, exacerbated by generous suspension travel. In extremis the system could “jack-up” in the best VW Beetle and Triumph Herald manner. According to the same Autocar article, the Zephyr didn’t even ride well: “Another aspect where the car disappoints is in the comfort of the suspension. The ride is harsh and decidedly noisy, every dip and ridge seeming to thump through the body, first at the front and then the back.”

There’s a possibility that Ford had tried to alleviate the system’s failings by stiffening the suspension and damping.  It is also suggested that the cars’ nose-heavy weight distribution and a high rear roll centre worsened the problem.

The last all-British big Fords’ chassis remained fundamentally unaltered throughout its six year product cycle.  The only acknowledged improvement was the adoption of radial-ply tyres across the range not long after introduction. These increased steering effort considerably, so gearing was lowered from 5.5 turns lock to lock to 6.4 turns. The ship-like steering gearing may also have served to discourage the sort of heroics at the helm which brought out the worst in the car’s rear suspension.

Lessons were learnt, largely at the BMW, and possibly Triumph and Peugeot fountainheads. I conclude with a couple of pictures of how it was done for the Consul / Granada. Plunging CV joints both ends, and not a swinging shackle in sight.