On an 05 XK8 what is the stock wheel offset? I'm looking at stock chrome wheels and aftermarket as well. Is the offset different front vs. rear?

 

I checked Google and it says +33 in front and rear. A +40 would move the wheel out not in , correct?

 

Depends if you have staggered wheels or not, larger width on rear. With staggered rims the front is 35 and the rear 33. You can vary the offset quite a bit but what you can't change is the overall tire/rim rolling diameter more than about 3% from stock otherwise you will get traction control errors.

There are quite a few tire/rim comparison programs to help you figure this out, just google tire/rim calculator.

See here for my adventure with new wheels..
https://www.jaguarforums.com/forum/x...-shoes-144124/

 

+40 moves the wheel in (the wheel hub face is offset out 40mm from centerline)

XK8 Fenders will fit an 8" wide wheel with 0 offset (about 1.3" out from stock). There will likely be additional bearing loading and ride height reduction from the longer lever arm, but they will physically fit without tire rub.

The wider the wheel, the closer you need to get to 33mm, so you could not get away with a zero offset wheel with a 9.5" rim as you could with an 8" rim.