To keep the chassis of the XJR calm it is recommended to refer to the well-known bearing and mounting specialist Emil Schwarz. He offers high precise bearings for the XJR swing arm and the headset. The stock clearance is eliminated and it keeps the chassis calm. You will be surprised how huge the difference is during driving. Most XJR have a huge stock clearance of the bearings. That leads to a jittery drive in fast driven turns. That is not only annoying but also reduces the fun of driving and the safety.