It would be tempting to put the 17 inch S model wheels on the XJ40 with more sporty tires than the 205/70/15 ones.

I haven't done it, but it sounds nice. I assume the offset is the same or appropriate. Maybe try the general technical forum.

I did use 15" XJ40 wheels with 215/70-15 Michelin Arctic Alpines on my 1995 X300 no problem (stock 225/60-16). That was a very sticky, quiet and comfortable combination for (gasp!) winter driving.

I used to . I switched to 16" X300 Turbine Wheels with Michelin Primacy . Results ? I hit my head a few times to the headliner when going over the bumps . I got back tofactory 15" Roulettes since then no hitting my head lol
Seriously riding is smoother with 15"s than 16"s
I also posted my review on the wheels forum , you are welcome to look at it

With 15 inch wheels do you have to use 205/70/15 tires? Or can you use 225/60/15? I saw some cool 15 inch Jag wheels that would fit my car but they were 15X6 1/2 instead of 15X7. If the 15X6 1/2 could still fit 215/50/15 tires that would be cool. Would that be too low to the ground?

I use 225 / 60 / 15 , correct size . I think you mean pre '91 earlier XJ40's wheels because those quirk numbers suggest that wheels to me lol
With those wheels (if I get it correctly in my statement above ) only size you could use is 220 / 65 VR 390 . Dunlop made them don't know still makes them

Why do you try a different size , I didn't get

When you say "S Model" are you referring to a modern S-Type? If so, better check the bolt pattern. I'm 99% sure they won't fit your XJ40.

Cheers
DD

The 225/60x15 tires should be be OK for the car and the 6.5" rim.

A 215/50x15 tire probably would be too "short" or low to the ground, yes.

Cheers
DD

I don't think any of the USA market XJ40s used the 390mm wheels.


Cheers
DD

I found a website where you can get Jag wheels. It lists which years they will fit. My current wheels are 15X7. The ones I am thinking of getting are 15X 6 1/2 like you said.

88-94 Jaguar XJ Factory Wheels from Capital Wheels at Andy's Auto Sport

I am about to switch to the 16" Dimple Alloys with 225/60 16" tires. Havn't seen them yet. Gonna go this morning. Is the ride THAT much rougher? I was thinking about changing, because it seems that they are phasing out the 15" high speed sport tires. There seems to be a better selection in the 16" range. (the new 15") lol Also, was wondering about all of the cheap import tires out there. Lots of S and T ratings, not many H, V, and Z's . Sorry, not trying to hijack the thread.

It's the tires, not the wheels.

Broadly speaking, the lower the profile, the firmer the ride will be. So, a 60-series will be firmer than a 70-series and a 50-series will be firmer than a 60-series, etc. As the tire sidewall gets smaller there's less ability to soak up the bumps.

But, again, that's broadly speaking. There are differences in tire construction that come into play.

Those V/Z/W speed rating tires generally have a very stiff casing. The S/T rated tires, not so much.

Cheers
DD

Would I have to worry about bottoming out with the 225/60/15 tires with the 15X7 wheel?

I switched to the 17's off of a XK8 fit perfect and very little mileage change.

I think it looks much better to.

would any xk8 wheels fit on a xj40 or do certain wheels fit especially over the hub .

I have 225/60r16 wheels on mine off of an xjs and they look great and don't rub

I bought mine with 16s on it and it is a pig. Go around round abouts just a little too fast and it will rub. Actually make that any corner.
I am looking at taking it back down to 15s.

Mine came with 16's on it. Stock size for the 94 I thought. I've never had any type of rubbing issues.