I have a 1998 jaguar xj8 right now i have 18 inch rims on the car i want to go up 2 inches to 20's my question is will 20 inch rims with 245 35 20 tires fit on with no rub or problems at all. i would also like to know if i would need to change anything like the brakes bearings or anything else.

 

Are you sure you want to do this? The stance of the car will get strange IMO and the ride will be trashed with minimal improvement except at the outer limits.
We have seen members trying to go back to stock size wheels after bad experiences and you will not be able to get your money out of the 20" wheels. These big wheels are prone to curb rash and inside rim bending
over bumps that usually get leveled. You can not sell a curb rashed wheel
except for snow tires and 20 inchers are not suitable for that.
THink it over.

 

I just bought used 19" rims for my 97 xj6 they came off a 95 xj6. The guy has been running 245 35 19 tires and he didn't mention any problems not sure if the xj8s differ.
In my opinion 18s are too small for a xj6 or xj8 thats why I was stoked to find 19s that actually came off the same type of car so I know they work.
They should be mounted on my car tomorrow or the next day. I will let you know if I notice any problems.
IMO 20s will really set off your Jag & look 50x more than your 18s although you will be losing some benefits of course to me its worth driving a little more cautious than to run small rims but thats just me.
& in regards to your question about whether you need to replace brakes, etc.. You may not "need" to right away but it would be wise to upgrade to drill&slot rotors as bigger rims are usually heavier which will put a lot more strain on your brakes, etc.
I plan on replacing my OEM rotors with drill&slot rotors & replacing the tie rods as soon as I am able to afford to do so. It will be a lot safer to drive & you will have better stopping distance as well as peace of mind