A grand tourer like the XKR errs on the side of ride comfort more than a sports car like the Porsche 911. So the ride is firm without being harsh, but a stiffer chassis would eliminate shudders over really rough stuff. At its handling limits the Jag understeers uncomfortably, and the too-light steering is devoid of feedback. But keep it at about 8/10 and the steering’s quick ratio, the big tires and the car’s roll resistance and sharp responses combine for an enjoyable mountain road run. The traction control comes on subtly but early; shutting it off increases understeer, but with so much power you can kick the tail out with a little creative effort.