Cars and TWR to produce high performance sports cars) England from 1990 to 1992 and had no official involvement from Jaguar itself. Design and reception The XJR-15 is powered by a , naturally aspirated 24-valve Jaguar V12 engine. The engine features an advanced electronically managed fuel injection system with a very advanced (for its time) 'fly by wire' throttle. The standard transmission is a TWR unsynchronised six-speed manual transmission while a five-speed, synchromesh transmission was also available as an optional extra. The XJR-15's chassis and bodywork are composed of carbon fibre and Kevlar (it was the first road-going car built entirely of carbon and Kevlar composites, before the McLaren F1 used similar construction techniques in 1992). The overall proportions differed from the XJR-9, with the XJR-15 being 480 cm long, 190 cm wide and 110 cm tall. The final weight amounted to be . A fully independent suspension was used, with non-adjustable Bilstein shock absorbers all round. Front suspension consists of wide-based wishbones and working push-rods to spring damper units mounted horizontally across the centre of the car. The car retains the rear suspension unit from the XJR-9 with vertical coil-springs mounted in units with uprights within the rear wheels, allowing for the maximum possible venturi tunnels. The engine forms a stressed member for the rear-frame. The bottom of the car is completely flat, in line with Group C practice. The brakes are steel disc units with AP four-piston callipers. The XJR-15 has a 0–60 mph time of 3.9 seconds and a (gearing limited) top speed of . The ride height was somewhat higher than required to take full advantage of under-body aerodynamics due to the road going nature of the car. Additionally, the suspension was softer than would be found on the XJR-9 racer and - in a last-minute deal - Tom Walkinshaw switched tyre suppliers from Goodyear to Bridgestone just before the race series started. When interviewed by Autosport in 2011, Ian Flux recalled: "The worst thing was that Tom had done a deal with Bridgestone. At first, it was going to be on road tyres, but then they changed to slicks and wets. The fronts weren't a problem, but they didn't have moulds for the rears, so used F40 moulds instead. They went off very quickly and it was hard to judge how hard to push." As Tiff Needell, who road-tested a development car at Silverstone early