I am refering to the OP's wheels. I believe he said they where 8.5x20 and 9.5x20. Just looking fir the correct size tires to keep every thing as the stock overall diameter front and back.

 

To stay at the 27" diameter then you need 255/35-20 all
The way around.

 

Factory size should be - 235/50-18 - Diameter: 27.3"

XKR Wheels - 275/35-19 - Diameter: 26.6"
Front - 245/40-19 - Diameter: 26.7"

Very slight difference. It isn't noticeable.

 

Accuracy cannot be that important. Consider this: Tire diameter varies from manufacturer to manufacturer just look at the specs from Pirelli, Michelin, Dunlop, Bridgestone, etc., 18" tires are going to vary from 27.1"-27.3", 19" & 20" tires 27"-27.1" but as they wear, they are going to get smaller anyway. The new XJ tire diameter is 27.5"-27.7" @ 19" & 20" .

 

Agreed. As long as you stay close in size within .2-.4" of stock. And make sure you have clearance at full compression and lock to lock.

 

04XJ8 the sizes you gave where for the XKR's 19 inch wheels. I am looking for the correct tire sizes for an 04xj8 with the opening posters 20 in wheels. Any idea? Every post that comes up everyone says a different size. I just want to make sure that I order the right size tires front and back so I am as close to stock rolling diameter as possible.

 

I replied to your post above with the correct size.

 

Jahummer. I appreciate your help. Those sizes you are talking about are for the 19" xkr setna wheel correct? The OP has the 20" version so the sizes you listed would be incorrect no?

 

In post # 62 I said you needed 255/35-20 which is the correct tire for the OP's rims.

 

Ahh I see what your saying lol sorry! Last question I promise lol. Since the wheels are staggered at 8.5 and 9.5 the 8.5 is 255 but shouldn't the 9.5 be wider?

 

Oh, thought they were 8.5 all around. You can still use the 255/35 as they will fit up to a 10" rim.

If you want staggered tires too, then you will have to chose a smaller or larger diameter as discussed previously, 245/35-20 & 275/30-20 @ 26.5" or 245/40-20 & 275/35-20 @ 27.5". My recommendation is to go with the larger diameter for comfort and speedo accuracy (as the tires wear they will become the correct diameter whereas if you start off smaller, they are only going to get smaller further reducing speedo accuracy).

 

Now we are on the same page! Thank you so much for your help, your post really cleared things up! Only problem with the 245/40-20 & 275/35-20 is those tires are $$$. Cannot seem to find a good deal on that set up.

The seller Jaguar Wheels SKU 010 20 Inch Silver Rims With Tires Free Shipping
has a package deal with Falken FK-452 255/35R20 & 285/30r20.

Is there a reason you chose 245's and 275's instead of the sellers 255/285?

 

I really need some help because I want to do this right. I want to get new rims for my 2004 XJ8, but I'm not sure if I should get the 18" or 20" rims. If I go with the 20" rims, will the ride comfort decrease significantly? Will the air suspension undergo problems adjusting to the new wheel size?

 

I just mounted my 20" summer wheels a few days ago. The car is still pretty comfortable, I mean it is a Jag, but the ride comfort has definitely dropped compared to the stock 18s.

Stick to good roads and you'll be fine. I definitely am going to avoid certain routes when driving. The looks are worth the cost to ride comfort in my opinion. (I will upload pictures of my set-up in a couple days )

The wheels are 255/35/20 for reference.

 

How would you describe the difference between driving with the 18s and the 20s? Since I'm from LA the roads are a nightmare with potholes. However, my brother has 20s on his XK8 and the car still seems fine. I would love to see your pics as well. Thanks!

 

Well, I think the best way to put it is you feel more connected to the road. W/ the stock tires on it always felt like you were just floating when driving, but now you feel the road more, hear it more, and the steering holds more meaning. It's still a comfortable ride, but on really rough terrain its a bit jarring. No worse than my old Acura TL Type-S but that was meant to be a sportier car.

I like it, I don't think the difference in ride quality or road noise is anything to worry about. Plus the looks are well worth it, and the improved steering feel, (which might all be in my head lol), makes dodging potholes and puddles that much easier.

 

Thank you for your input! I'm going tomorrow morning to see what 20" rims I can place on my XJ8. I'm thinking about getting some that have a decent amount of spokes so it has that classic high-quality look. I also want to make sure the tires are flush inside the wheel wells and don't stick-out.

 

Very useful posts folks. Pictures speak a thousand words. I have similar car and think I'm going to go with the 20's.
I was going to order some 19" rims today (more expensive than 20's), primarily because I wasn't sure if the 20"s would diminish the conservative look I love about my car and wasn't sure if the ride would change for the worse.

That doesn't seem to be an issue it would seem?

I'm a newbie, any comments/feedback/opinion on going with the 20's would be greatly appreciated.

 

Well, for some reason, I can't fit anything wider than 8.5 on mine without it rubbing and tearing up the wheel well.

 

OK, I'm having the hardest time finding 20" rims for my XJ8! I've been researching and going to wheel shops and they cant find what I want. Many of the styles I want are not able to fit on my vehicle. All they have are these ugly ghetto-gangster rims. Then, most of the vendors say that the wheels available for my car all have caps instead of exposed lug-nuts. I hate caps!! All I want is a rim that looks like the 10 spoke XJR rims or the 5 spoke Super V8. I would buy these original rims, but they are too expensive, even without the tires. I just want similar rims with exposed lugs and to come with a tire package. Can anyone recommend some rims???