I was wondering if anyone has put wider tires on the rear of these cars. I have read almost all the article from the XF, XK and XJ. They all pretty much have the same engine, trans and weight. The only major difference is the tire size on the Xk is wider. The XJR is about .5 second slower than the XKR. Is it possible to get a 285/35/19 on a 19x8.5 rim? I think the 0-60 could drop a .5 second and keep with the XKR. The only factor I can think of that would keep the XKR faster is shorter wheel base that transfers weight better and if the rear end has a larger gear or LSD. I know my 04 with 255/40/19 can spin the wheels at 30 MPH.

 

If you put wider wheels on back, sure traction will be better but 0-60 times will be slower, the XKR weights 3,690 lbs where XJR weights 3,946 lb and ofcourse XKR has a shorter and lighter drive shaft, the LSD and gears remain same though.

 

The 0-60 would be slower than the stock XJR or still slower than the XKR?

 

It will be slower than the stock XJR

How do i know this?

I actually tried this on my S500 back in time , i had better grip on high speed corners tho so it was worth it

 

I've read several articles that suggest wider (therefore larger) tires increase unsprung weight and can reduce acceleration. However one would think that a wider tire would have better traction at launch.

 

I agree with the additional unsprung weight, If you don't have enought power to offset it. My 04 XJR has power to spair and I have spun the tires at 30. If your car couldn't spin the tires off the line and you put a wider tire on...it would definately slow the car down because of weight.