Original sizes for XJ6 and XJ12 were 205/70VR15 (6s) and 215/70/VR15 (V12s). I had an XJ6 Series 3 for 14 years 1988-2002.

 

Yes, the V12 is very heavy. Many find that changing the front springs to XJ6 springs brings the nose down to an acceptable level.

Mine was a tad nose down with the 4.2. The lighter LT1 allowed it to raise up just a tad. Too bad, in away as it looked neat with a slight forward rake. The hnot rod blood in me, I suppose!!

Tire diameters between makers is quite variable. Mine is now shod with B.F. Goodrich 215 x 70- x 15 on &' XJS lattice wheels. Just right as to stance and the wheel tire combo fills the wheel wells with no suspension or tin interference. The only drawback is that the spare is a Kent as the others are too tall for the spare well. As it is, it takes just a tad of adjustment to fit the lid.

Again, a very nice car. A well done lump makes a fine combination. Mine goes to SMOG today or the next day. Ugh.

Carl

Carl