I was looking to install a set of Senta 20 rims, the beauty for us S-Type is if we buy a XJR/XKR/XFR in the future, we already have rims that will fit on them...While I was shopping, I had a tire go flat and I decided to scrap the idea and get 4 new OEM-size tires...But man are Sentas cheap, on ebay 4 staggered sliver clones are $699 shipped and used authentics went as low as $800 shipped and there is a set for $950 shipped, as of today...Thought I'd share my findings...

The fronts: While an half inch wider at 8.5" will bolt up to the S-Type fine. A close size to keeping your speedo close would be p245 30 R 20, this is also the safe bet for keeping the fronts from rubbing. 255s will fit on the rim, just am not 100% if they'd rub or not...

The rears: The XJR/XKR/XFR rims have a 26mm offset and will not fit the S-Types 60mm offset as is, you're off by 34mm...They make wheel adapters, they usually go by american units, so 4.25" x 5 to 4.25" x 5, if you want to go cheap, for about $70 shipped, you can get a pair that are 1.25" deep which still puts you 11mm shy of the 60mm S-Type offset, but they make cheap 11mm spacers that will put you where you need to be. You could also ask a company to custom make a 34mm/1.34" deep adapter but I assume that'll be very pricey.
For the rear tires a 285 25 R 20 is pretty close in overall diameter to OEM...

 

Those Sentas look good and the price is very tempting, but based on what I've read in multiple previous posts it seems there are a lot of good reasons not to run 20s on our cars.

 

https://www.jaguarforums.com/forum/s...oes-tint-2524/

Unlike others, I have actually had direct experience, I had 20s for nearly four years...Lots of good reasons to have 20s, in fact, all current models of Jaguar offer them from the factory in some trim level...

 

I don't have any direct experience with 20s on a Jag. Part of my reason for being here is to soak up knowledge from all of you good folks. I've read a lot of comments concerning added weight, decreased handling performance, decreased braking performance, harsher ride and one member called them downright unsafe. I'm certainly up for being talked into 20s. I'd be very interested in hearing the positive side if you're willing to share. I'm guessing they must have been on your '03 that you parted with. I understand that the '08 STR came with 19s. Kind of like to find a factory set of those.

 

Spacers would in effect make the offset of the wheel even lower. A wheel with a 26mm offset paired with an 11mm spacer would be more the equivalent of having a wheel with a 15mm offset, not 37mm.

 

I did have them on my '07, non-STR...A lot of what you've read about decreased performance with upsizing is wrong, in most categories you increase performance...Here's a fun article:
Effects of Upsized Wheels and Tires Tested - Tech Dept. - Car and Driver

Thanks for pointing that out, I've never used spacers so I stand corrected, I was given bad information...So, that means adapters would also subtract and therefore this thread is entirely pointless as there's no way to get 26mm offset wheel to fit cost effectively...lol

 

From that article, upsizing past some point reduced grip and performance. Also, they didn't try any tires narrower than the OE tires, which is what one member here has.

I suppose ignore its comments on understeer as that was FWD car and ours are RWD. For that matter, they're such different cars maybe any conclusions are moot.

 

Time to put some 15s on the STR!!

 

Go for it, but not on a public road please.

They won't clear the brakes, of course.

 

Downgrade to 3.0 rotors...15x6s w/185 wide tires...The car will feel like it's on nitrous since you're shredding around 200lb in unsprung weight...Good luck launching, though...Since just about every thread goes off topic...Has anyone noticed if going from stock suspension to H&R/bilsteins if their 60's have increased?