Hello All. I haven’t sat down to do my intro yet, but I’m already in need of more advice… Clueless!
So right to it… I achieved my #1 goal of acquiring a set of Apollo wheels that bring my car back to factory stock… well, almost stock👺

The recommended REAR tire size on the stock 2003 XK8 19” Apollo Alloy is…. 255/40r19. (Front is 245/40r19)

With Purely cosmetic motives…I’d like to get a Meaty-er Stance in the back. To me, the 255/40 tire does not look wide enough for the Apollo 9” wide rim…for my taste.
Even if I used wheel spacers (Which I do NOT want to do) to widen the car’s stance, the tires will still look thin/wimpy for the wheel width to me.

I’d like to put these instead…. Continental Exremecontact DWS06 Plus… 265/40zr19 just a tad wider(0.40”) and a niblet taller(0.30) total diameter.

( I excluded size 265/35r19 - which has a shorter sidewall than the stock 255/40r19, as 1/2 my Meatyness-goal is a slightly taller tire too fill the well-gap.)

Big Question #1 = Am I messing with the Car’s brain or spec-precise suspension adjustments, or ANY significant systems by using a slightly off sized tires?
If so, can these new parameters be adjusted by Jaguar tech programmer to avoid any problems.?

Question #2 = With independent suspension on rears, don’t the top of the wheels fold inwardly when shocks compress, avoiding the Body panel above the wheel well?

I’m hoping so! That should easily eliminate issues with this slight tire width, as it concerns the body. On my old Camaro, with a straight rear axle, the wheels went straight up into the inner-fold of the rear fender body panel. Sliced up the sidewalls efficiently when the air shocks blew! Ahhh, Memories!

As often lately, I truly appreciate all your help and comments. I intend to give back when I get my tires warmed up here in this awesome place.
If there is a thread about this already, please direct me to it. I couldn’t find one. Thanks again guys, especially you “OLD FAITHFUL “ advisors!
Priceless!
So please stop me now if I need to stay STRICTLY STOCK.

Below are the measurements of the recommended stock size and my larger preference.

(Stock)
255/40-19 265/40-19 Difference
————- ————- —————
Diameter - inches (mm) 27.03 (686.6). 27.35 (694.6). 0.31 (8) 1.2%

Width - inches (mm) 10.04 (255). 10.43 (265) 0.39 (10) 3.9%

Circum. - inches (mm) 84.92 (2157.02) 85.91 (2182.15). 0.99 (25.13) 1.2%

Sidewall Height - in. (mm) 4.02 (102) 4.17 (106). 0.16 (4) 3.9%

Revolutions per - mile (km) 746.1 (463.6). 737.5 (458.26). -8.59 (-5.34) -1.2%

 

Question #2. I have never taken a good look at the travel of the rear suspension but the lower control arm slopes slightly down in normal stance so l would expect the arc of wheel travel to move it only slightly outward before it moves inward. The camber would remain more or less the same throughout it's range.
I don't know if the abs would throw a hissy over the tyre mismatch, l doubt it would but you could avoid it for sure by going with your 265 at the rear and upping the front to 255.
For certain there is no programmable solution.

 

Hey baxtor. I see what you are saying with the suspension folding up and possibly outwards.
It sounds reasonable, but hopefully a specialist will chime in with more details.

I guess I don’t understand why the front tires being larger allow the rears to work better.
I’m good with getting 255’s for the fronts if that works better with 265’s in rear.
I guess I need to research tire size matches for the future…
for now I’ll take all the good advice I can get. Thanks Baxtor!

 

it's not so much that they are wider but that with the same sidewall ratio wider also means taller. By running 265/40 on the rear and 255/40 on the front it more or less keeps the difference front to rear at about the same as the original stagger.
We know the systems have no problem with the original stagger, but not sure at what point stretching the difference between front to rear circumference does become a problem.

 

Gotcha! Makes perfect sense! Thanks again for stepping up. Not the most important question for this high-knowledge base… I just want this to be righteous the first try.

 

since January 2021, I am running 245/35r20 in front and 265/35r20 in rear; car handles and rides great also loves its stance.
no bottom out or rubbing.

 

The speedometer will be off by a fraction, due to the taller rear tire. Clearance should not be an issue, as the new spec width will not be greater than 3/4". The back spacing to the rear will accommodate an 11 inch wide wheel, provided proper offset. FYI, stock 20" BBS wheels are 20x9 front and 20x10 rear. Just realize you are adding additional weight to the driveline = reduced performance, mileage, increased bushing wear and more body roll when cornering.
Speaking from experience.

 

Nice wheel choice.