Sean,

To sum up my understanding of the general compromises involved in selecting a wheel/tire ratio:

The larger the wheel and lower the tire aspect ratio/sidewall height, the better the steering and handling, but the harsher the ride; also, the greater unsprung weight, because most aluminum wheels weigh more than the equivalent diameter of air-filled tire, resulting in reduced suspension damping efficiency and some additional loss of nimbleness and ride comfort.

The smaller the wheel and the larger the tire aspect ratio/sidewall height, the worse the steering and handling due to increased tire roll when cornering, but the greater the comfort due to increased air compliance in the tire.

Just to add another brand of tire to consider, I have had great success with Yokohamas on our Jaguars for their combination of ride quality, great handling and precise steering, low noise, decent treadlife, and lower cost compared to Michelin and Pirelli. Their current model is called the AVID ENVigor, which isn't rated well for snow and ice but otherwise is rated competitively with, and even superior to, some of the Michelin Pilot models and Pirelli P Zeros, yet at a significantly lower cost. When the Pirellis on our X350 wear out, I will definitely be considering Yokos for the next set.

My two cents!

Cheers,

Don

 

Well my Tucana wheels arrived this week. I did a quick check for clearance fitment and having the Michelin Pilot MXM4 V rated tires (235x50Rx18) installed today. Here in Minnesota, the tires run $946 after tax and rebate of $70. Includes mount valve stems, balance and lifetime rotation. I still can't see the grass (snow cover), but we've had enough rain that all the salt is off the roads. Almost cruising time!!!
I will keep the 19" OEM with Blizzaks on them in the garage in case I ever decide to drive in snow, though not bloody likely.
Thank you to everyone for your help!

 

Just to add that early on (2003/4 ish) there was a 17"x7½ wheel option (named 'Elegant'), supposedly for winter tyres. That took a 235/55 17 tyre.

 

I run 18 inch Coventry wheels on my 2004 XJR for the winter. The car came with the extra set of winter wheels, so I do not know the offset or diameter. Also have an 18 inch spare which appears to fit just fine when fitted on the front with Brembo brakes
RyeJag

 

The offset of the 17" OEM Jaguar wheels is exactly the same than the one of the OEM 18". I also have a 17" set for winter in addition to my set of 18" Coventry. Btw, the 17" are forged and much lighter, very nice wheels!