I previously asked what were the largest tires to fit on the XJ8. I really wanted to know what was the widest tires to fit. I wanted as much footprint as possible.

 

Are you speaking straight out, what is the widest that will fit or what will fit for the rims you have? It depends on the rim width amigo, that tells everything. Once you have that, along with diameter, then go to any tire dealers site and see what they have that fits.
If your changing rims to 3rd party ones, then you best take into consideration the turning radius if wanting 20's+ ....then think of the width. The larger round your rim, the deeper it turns into the well while cornering and there's only so much room there. Add the width and it is deeper yet and your fender lip soon becomes a victim. You can make a 30' turning radius into a 40' one with improper fitted shoes.
I'm sure there will be some more specific statements forthcoming for what they've experienced.

 

 

Ok, then go here... https://www.wheel-size.com/size/jagu...m-40i-xjr-eudm ...find your standard wheel for your Jag and determine the size tire. I have an R model with 18x8's standard. Depending on the model and suspension option, you need to find it on that site and go from there. They even give you the tire size specced for it. Mind you tires have come a long way since then, so take your rim size to other sites and see what options are available. I would stay away from low profile, you'll find they tend to ride like a truck and rim damage is easier.