its a simple matter to check wheels you suspect are bent or not running true. this problem can be detected quite easily on a tyre balancing machine. although jaguar had addressed the problems of quality and reliability on later models xjs jag s still had problems. when you start to look closely at these cars you begin to wonder what the hell did jaguar have in mind. some examples being poor air ventilation under the bonnet and engine area., and also very poor air intake, for such a large motor. some of the vacuum hoses actually sit just above the exhaust manifolds. all the fuel injection electrical loom and wiring for the motor sits on top of the motor , which over the years is destroyed by the severe under bonnet temperatures. i do think that maybe if jaguar had used bosch electrical systems on earlier cars we would not have the problems we have today. when you actually look into a xjs engine bay it certainly looks like they threw the big lump v12 into position and the electrical wiring and components were a after thought. a lot of people that own these cars are probably not aware that originally jaguar planned to mid mount the motor