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XJ Suspension Set-up

FebQAsuspension]Q Hello from Denmark! Out here Jaguars are not so common, even rarer are those wishing to modify them! I am doing just that to my XJ6 4.2 Series 1. Whilst fitting such improvements as six throttle bodies (on a Weber manifold) with an Emerald engine management system, my main concern is to ensure the brakes and suspension are up to the job. Two questions: what is involved in fitting the later four-pot calipers and ventilated discs and what suspension settings should I employ for fast road and mild track day use? I am fitting 16in wheels, Toyo T1-R tyres, HBE anti-roll bars, Aston DB7 springs, Gaz adjustable dampers and SuperFlex polyurethane bushes.

Christian Christiansen, via email

A Source a set of complete 1976-on XJ series uprights; ensure they are the later ‘fat’ stub-axle variant – recognisable by the plain nut/castle cap wheel bearing adjustment (as opposed to castle nut); also acquire the ‘handed’ lower wishbones. This will provide a simple bolt on conversion, but remember – unlike the imperial Series 1 – the later calipers have metric threads. Add braided flexible hoses, Mintex M1144 pads and Castrol React Performance brake fluid and you will achieve confident pedal feel with a high degree of fade resistance – obviously other makes are available!

Suspension set-up is a matter of personal preference (just ask Jenson and Lewis!) but for the purposes you mention, we would recommend ¾ degree negative camber (that is, the wheel ‘leaning in’ at the top), the maximum achievable positive castor and 1/8in toe in – obviously both sides must be equal. Go for ½ degree negative camber at the rear and ‘click 8’ on all six Gaz dampers. This should give you a good baseline to meet your needs. When refining further, avoid excessive front end negative camber – on a road car it will manifest itself in straight line instability and poor braking performance caused by wheel locking due to the minimised tyre contact patch. You will notice we implied retaining the S1 top wishbones – these have rearward ‘stagger’ and allow greater positive castor settings to be achieved – a trick initially employed by Jaguar themselves on the V12 fuel injected cars. 


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