What are the weakest points of XKR-S?
 

How can one improve XKR-S? I can think of

1. Better rubber
2. Better suspension setup?
3. etc?

Increasing power is easy, just do a pulley, good exhaust, and a tune. Power is nothing though w/o handling. Still, I wonder if anyone has tried swapping the cat for the hi-flow version?

I also wonder if XKR-S GT parts (e.g. suspension) would fit regular XKR-S. From what I understand, the main focus of GT was suspension and aero.

Thanks

I can't comment on the suspension of the XKR-S as I own an XKR but I would say 305s in the back, I've even heard of 335s but didn't see them in person. High flow cats as well if you want a little more power. From what I've read the GT has quite a few different suspension components and wider track so I'm not sure of the parts are swappable unless you do a wholesale change of components. Plus the parts are insanely expensive, I was quoted 2800 by my dealer for the rear sway bar. I would also believe, at least in my conversations with Spires that an Adaptive suspension compliant Coilover setup with properly tuned dampers and proper corner weighting would be an advantage.

Spires? Is it one the vendors here? I plan on doing 305 in the back when I need to buy new rubber.

From my own research of the past few months, as far as Jaguars go they seem to one of the better at understanding chassis dynamics for these cars. With most other makes Porsche, Corvette, Ferrari etc there are dozens of shops and loads of knowledge available. Heres a link to a few articles written about their cars. Reviews

They also modified a previous gen 2008 XKR-S and have been doing lot of XFRs lately. I'm in the process of specing out coilovers with the proper spring rates and dampers now. I should have my car back with the 305s today :) Can't wait its been in the shop for 2 weeks!

I also meant to add, although they do not list the XKR-S they are capable of custom set ups that meet any of the current XK series cars.

Thank you for the link. let us know how you like your new setup. Any rubbing issues with 305 in the back?

BTW, are you changing tires upfront too, or rear only? In the back, can you list the maker and the size 305/??/??

Blue, are you thinking of improving the car for track use? or street?


Rich

Mostly street. I just feel a need to change something to get better straight line performance .... :) I like messing with my cars even though XKR-S is not the right car to mess with. It's great GT cruiser as is

The tires I'm running are
265/35ZR-20 Michelin Pilot Super Sport
305/30ZR-20 Michelin Pilot Super Sport

I just got back for the shop and unfortunately ADV got the rear offset off by 1/2", so now I am going to have to wait on new rear wheels.

Why did you go with new wheels? Do you know if 305 fits on stock XKR-S 20" wheels?

Quite. I'm thinking it would be very easy to spend a lot of money to end up making it drive and handle significantly worse, and be worth a lot less.

Avos's twin-screw SC kit might be an option if he ever makes one to fit 5.0 engines. His (old-shape) 4.0 XKR is now making about 630 hp with it (from stock of about 390).

I just wanted a different set of wheels. They came out perfect except for the rear offset. Now I'm hoping I don't have to wait another 2 months for them to make another set of rears.

Both of these fit with no rubbing or clearance issues on the stock 20" wheels:
265/35ZR-20 Michelin Pilot Super Sport
305/30ZR-20 Michelin Pilot Super Sport

Stiffer springs will help and get the widest - stickiest tires you can.

Also, understand that the tires need to be heated up to really work well.

Pobst told me regarding the XKR-S.... "Get the GT springs that will help a lot"

Main thing is for most of the aero the benefits occur at high speeds... Not as big a deal at slower speeds... Now.... Anybody know how we can get springs they only made 30 sets of????!? :(

Suspension setup takes a lot of trial-error type testing, unless someone else had already done the tuning. When I set-up my high performance street and track race cars I tried a very large number of springs with different rates, different ride heights, different damper rates and different size swaybars and bushings. So, what I am trying to say is that you can spend an awful lot of time and money changing things and NOT improving anything but, actually making it worse.

So, my recommendation, is to wait until a well proven setup shows up on the aftermarket (may never) and go that way. Otherwise, you may just throw money to the wind and mess up the car. Remember, there is ALWAYS a negative trade off for increased performance. The question is what it will be and can you live with it?

If you only want straight line improvement, get the widest and softest compound tires. I feel that anything with a SC 550 HP engine need more tires than what the Jags have.

Albert

I'm going to leave my car stock. If I was going to track my car, it would be a different story. The Xkr-s actually has good grip and cornering ability for the street. There is just a tendency to oversteer if u apply the throttle too early, but it actually makes the car fun to drive!
My only mod will be to go with michelin PSS at 10mm larger size front and rear like another Xkr-s owner on the board has done

^--- I agree...Upgrading to the slightly wider and much stickier PSS tires is a great start to help with grip.

I am surprised no review (or maybe I missed it) has mentioned the XKR-S GT has the PZero "Corsa" tires, which is an R comp tire and they are softer/stickier than the regular PZeros on the XKR-S.

I don't think the GT springs are the answer as it has a different suspension geometry there for spring and damper settings will be different. If you want true race suspension and adjustability go with Coilovers, get the ride height correct, then start having fun with damper settings and sway bars. I'm going through this now but am not going nuts like I have in the past with cars I tracked on a regular basis. I'm actually pretty happy with the current set up other then the rebound of the rear dampers.

Tires, tires, tires. Yes.

I'd save the money one might spend altering the suspension and use it for track time and instruction


Rich