Hi,

I have 285 30 20" rears
Is this the standard size?
What pressure should they be?

Id like to increase the profile to get a softer ride but how far can i go?

Regards,
Ross

 

Ross, not standard at all. Yours would have been the 17 inch 245/45 I think. That is really wide for the rear. Do you know which ream you have? Apollo?


Wayne

 

Another case of a prior owner going to 20's for the "look". If you can find a set of 18's you will be able to run 45 sections and be much more comfortable. It shouldn't be hard to sell the 20's.

 

On later years 20" rims were standard on some XKR configurations (it was standard on my 2004 Portfolio). Yours should have had: 1999 Jaguar XKR Convertible tire sizes (since mid-year 1999 for Europe )



245/45 ZR 18 (F); 255/45 ZR 18


Here is the Car and Driver review from your year: http://www.caranddriver.com/reviews/...-xkr-road-test

 

Thanks guys. I appreciate the quick response.

Any idea what id expect to pay for a set of 18" wheels?

Going back to my origonal question, what pressure should they be?

 

As others have said, 20 inch rims were never specified fro the 4.0 litre models. However, they were an option on the later 4.2 litre models.

The recommended pressures are on a label under the Centre Console Lid on the 4.2 litre cars. Although I don't have the car any longer, I do have a photo of the label.



Recommended pressure on 285 30R rears is 30 psi. As you can see from the label, there is no lower 'comfort' pressure recommended for this size.

With that kind of profile, dropping the pressure is not a good plan. It may be less harsh a ride but would increase the risk of sidewall damage.

Graham

 

Thanks GGG
much appreciated.

 

Which of the 20" styles do you have? I'm sure you could find someone to trade for a set of 18" wheels.

I would trade my 18" Hydra's for a set of Perseus any day of the week.

 

Search on 18" XKR wheel images and pick the look you like. Then search for them on eBay (XKR wheels). They show up from time to time because folks often want to go to 20s and don't know what to do with their old wheels. Or you can get them when someone is parting out a car. Personally I think the 20s look a ton better but its your car.

 

Everyone chants tire pressure like a religious mantra. No $2 tire gauge is going to measure pressure within 10% of actual. No $20 gauge is going to either. Start with the recommended pressure on your own, personal car specific tire gauge. Drive the car and observe the dust on the thread. Add/reduce pressure to the point that all tread is in contact with the road. That is the best pressure setting.

Tie a ribbon on that gauge and put it in the glove box.

Mine, on my marked gauge reads 28psi with the full width of the tire in contact with the ground. After lots of miles there is not any abnormal wear patterns on the tread.

 

FYI, Amazon sells a highly accurate/precise guage 5% or better as I recall for around $30. I've used it exclusively once I saw the huge difference only 1 or 2 lbs makes and calculated the error margin on other guages.

 

are you sure about that? My 2000 XKR had detroits fitted from the factory and tyre pressure for 285/30s are listed under the armrest

 

My 04 XKR came with 20" Detroits from the factory with Perelli Tires. It was not a comfortable ride. Tire pressure wasn't the issue. The tires had lots of tread life left but were old. I changed over ot Continental Extreme Contacts last spring. Same tire size, huge difference in the way they ride.

 

Here is a picture of the wheels that came on my car and what I changed them to.