I'm sure that somebody has done this before but I can't for the life of me find this information online. I would like to put some larger diameter tires on my 2005 XJR. I believe the stock diameter when converted from metric comes out to about 27 in. I was thinking of running 29s in the back, or at least a 28. I like that raked look that the 2003 and 2004 Mercury Marauders were able to achieve in a sedan, and would like a little more meat on the tires to absorb shock. Has anybody done this or does anybody know if it's possible without rubbing? Is it possible to increase the fronts to 28?

 

Use this website and enter in what you've got now and what you're proposing to fit instead. I have downsized my wheels from 19" to 17", as I want comfort ! The difference in tyre diameter was only 3mm.

https://tiresize.com/tyre-size-calculator/

Old was 255/40 R19, and new is 235/55 R17. Be careful when upsizing as the tyre width is the deciding factor. Jaguar are fitting some really crazy sizes now with 22" available on the F-Pace. What is the point of it all ? Does nobody want a comfortable ride anymore ?

 

I don't mind the comfort level of the 20" wheels I currently have, and I like the look. I am more concerned with the number of times I had to get these wheels straightened (and even welded once) due to the crazy terrain of NJ highways. I have spent more on repairing rims and new tires than I spent on the wheels and tires to begin with at this point. I was using Coventry Hornet 20s (which is part of the problem, as TSW wheels are garbage and I would not be having these issues if I had factory Jaguar wheels that would actually hold up to small potholes and such).

Anyway, the smallest wheel I can put on is an 18" due to the large brembo brakes of the XJR. I bought a set of Hornet 18x8.5s to run up front and plan on keeping the 20x8.5s in the back, but want to run a larger tire for both rim protection and to give it the "raked" stance. I like the way it looks on my Mercury Marauder (although the wheels are the same and they achieve the look with tire size alone,) and I think it would look pretty sick on the XJR. I believe the ABS tolerance would not be effected, but I am concerned with the tire rubbing. I just took the 20x10s off the back because they rubbed, but that was due to width, not diameter.

 

If you put larger tires diameter on the rear, it will messed up your speed, your real speed will be faster your speedometer indicated. I know you knew that.

 

It all depends on the diameter of the tyre/wheel combination. For me there was only a 3mm difference in changing wheel size from 19" to 17". The website I gave in my first reply also tells you what the speedo reading difference will be.

 

Thanks for bringing that up, but yes I am aware and it doesn't really bother me. I have been lifting trucks for years (like changing 31" tires to 44" and such) and I have become quite apt to calculating speedo variances without thought as I drive.

 

So does anyone have an actual answer to this? What is the largest tire diameter that can fit in the rear of an x350 XJR? I don't mean to sound pushy or rude here, but I really can't find this info anywhere and I'm currently riding on 3 spare wheels and need to get some new treads asap.

 

Almost everyone avoids fitting such large wheels. Of the rest maybe no-one happens to have read your question.

Maybe measure the space available then deduct a bit and hope...