Jaguar Suspension Development

Before I get round to adjusting the wheel cambers on the car, it is time for a history lesson with some of the background behnd the Jaguar's development of its suspension systems:

From the early 1960s to the present day virtually all serious racing cars have used the classic double wishbone suspension arrangement, or a close variation on the theme. There are many alternatives that have seen widespread use: beam axle, de Dion, swinging arm, trailing arm (even semi-trailing arm), sliding pillar (Morgan, unbelievably in this day and age), McPherson strut (front) and Chapman strut (same thing at rear), but for precise control of wheel movement and low unsprung weight, double wishbones remain the favourite. The beauty of the arrangement is that by careful design of the pivot points and arm lengths the camber of the wheel can be maintained close to the optimum even while the body rolls during cornering. Not only that but the roll centre - a term for the abstract point around which the car rolls when cornering - can be held consistent thereby helping to confer the vehicle with stable handling characteristics. Then there are ways of further refining the handling characteristics by angling the axes of the wishbones in various ways. For instance wheel toe-in and castor angle can be made to vary with body roll to enhance steering feel, or upward suspension deflection can be made to act against the forward weight transfer under braking to oppose front end dip. This is known as anti-dive and a similar arrangement in reverse, known as anti-squat, can be applied at the rear.

Jaguar's legendary Technical Director, William Heynes, knew that independent front suspension was essential for any car that claimed to be advanced and refined, so had adopted double wishbones at the front on the Mk V saloon just after WW2. However the case for independent rear suspension was not so clear cut and even the outstanding D Type had a live axle at the rear, which helps to explain why its greatest successes were nearly always at race tracks with the smoothest surfaces. Obviously this handicap would only become worse so Bob Knight and his team, with one eye on production applications, devised an independent rear suspension for an experimental successor to the D Type known as E2A. Within a year the E Type was launched (1961) with a productionised version of this same independent rear end, incorporating the now familiar rubber mountings as a vibration barrier and trailing arms to provide fore and aft control. It continued with only minor alterations until the last XJ-S left Browns Lane in 1996.

A notable but less well-known member of Bob Knight's team was Derrick White, highly regarded in club racing circles for creating his effective Impala racing car, later moving from Jaguar to be Chief Designer for the Cooper F1 team and then being credited for the Honda/Lola that enabled John Surtees to snatch a lucky win at the 1967 Italian GP. Talent was not a rare commodity at Jaguar in those days. The point of all this, of course, is to show that Jaguar were near the forefront of vehicle design with suspension systems technically superior to those of most other manufacturers of the time. It may not be obvious but Jaguar's well-known independent rear suspension assembly is geometrically very similar to the double wishbone system preferred by race car designers, in the way wheel camber is controlled. This becomes clearer when the pivot points are highlighted as in the accompanying diagram. Particularly notable is that the driveshaft doubles as the top link so that the under-floor space requirement is kept to the minimum.