Hi Chaps

Sorry if this has been asked a million times, I have read quite a lot of posts but can't find the exact answer.

I'm looking at taking a 2012 XKR Cab at the moment. I'm coming from having a few of performance cars (GTR (32/33/34/35, Audi RS5, RS6, S5, R8, Jag XFR, Merc C63 AMG, Supra etc etc). I based in the north of England where it is wet a lot of the time.

Now the question I have is around the wet handling, I've tested 3 XKR's and they all seem very twitchy when getting above 35-50% throttle. I'm not a hooligan (honest!) and tend to only really drive fast on track but sometimes it is important to have the confidence that the car is going to be stable when you have to get on the power. So I'm wondering if the cars were unstable due to tires, all the cars were running Dunlop tires 285 rear 255 front on 20" wheels or is it the characteristics of the car? Would different tires help? are there any other ways to improve traction? stability?

Even on a straight with the salesman driving he started to accelerate from 35-40 mph it kicked down and the back end went out.

The thing is I don't remember my XFR being like that don't get me wrong it would step out into over steer but you had to be really pushing on.

PS could anyone point me in the right direction regards to tuning i.e
After market ecu's? Engine tuning? Suspension?

PPS What sort of power has the drive train been tuned to my XFR was running 580hp and had no issues. Would the drive train/engine take more than that and how much? Just thinking about when I do the odd vmax event.

Sorry for all the questions!

Smokey

 

Maybe I'm misunderstanding you here, but the rear-end is stepping out on you, and you want more than the 510hp it already has?
In wet conditions, there's probably no tire that will contain that power. Others will probably chime in with their preferences for a dry traction tire.

 

Yeah, you'd probably just need new/different tires (NEVER MICHELIN!!!). That won't help much though, when the skinny is mashed.

 

Firstly welcome to the forum.
Tyres are the big issue here, when I got my XKR it had Falkens on it which I'd previously had on an Audi S4 and thought they were a great tyre, on the XKR they were junk! I've since put on a set of Pirellis and it's made a world of difference, don't get me wrong, this car is definitely still traction limited but a good set of tyres is a must!
Regarding tuning in the UK Spires is really your best bet (although I've no experience with them) there is also Paramount but they've had issues over the years. Sounds like you're no stranger to powerful cars so I won't lecture you but I'm not sure if you're after tuning that this car is the one for you due to the traction issue. The XKR-S has slightly wider rear wheels and came with 295 rear tyres rather than 285 to help this, but ultimately I think running more power than the XKR-S would be pointless, saying that if you were running 580hp in you XFR then you may be happy.
Either way happy hunting, it is a great car!

 

I have a plain old 2011 XK with Continental DWS 06 Tires on the 20" Kalimnos wheels. When driving normally in the rain I have no issues, and the Traction Control is quick to prevent wheel spin. There is also "snow mode" which will tone down the throttle response to give better control in bad weather. The 385hp of the regular XK is no slouch if you are more of a cruiser, and less of a racer

 

The rear end is too stiff in these cars. Softer rear springs and/or a stiffer front sway bar or softer rear sway bar is needed. There is almost no understeer engineered in. I've been meaning to do some research to see if someone makes an adjustable set of sway bars.

 

Adjustable sway bars or softer rear springs might be a way forward! Or dynamic adjustable suspension.

Thanks for tip on the snow mode! I bet your NA (which I'm sure is no slouch) means the cars got a better balance and usable power for everyday.


I agree on reflection I'm thinking more and more that those dunlops are just simply either too hard or have a poor tread pattern to offer good traction. Interestingly many moons ago I ran a 650+ MKIV Supra which obviously being RWD could be a handful but was much more planted. However it did have programmable suspension, smaller wheels with a larger tyre depth, adjustable aftermarket traction control and honestly it was very easy to control. I'm wondering if it possible with the Jag hmm

Just out of interest why not Michelin? Ran CUP2 on my track car and they helped me towards dropping over a second off my lap time compared to R888's at one of my local circuits. What would you recommend?

Yeah sorry, I meant more adjustable mapping i.e. Road mode circa 500 and track mode circa 600+ just for the track or runway. Agree 500 is plenty (more than enough) in the wet. It was just interesting how it started to snake sideways under load in a straight line. In comparison my old XKR would start to spin up, the TC would kick in but the car would remain planted.

 

 

Well there's a few things that are possible...

You can get a stiffer front sway bar https://www.jaguarforums.com/forum/x...ll-bar-167767/ the sway bars on the XK are the same as the XF, XJ, S-Type, F-Type.

You can get adjustable sway bar links SuperPro Sway Bar Links Heavy Duty Adjustable TRC1085 fits Jaguar XK 5.0 XKR-S | eBay

There's lots of options for coil-overs and lowering springs...

Funny enough when Jaguar made it's "hotrod" models like the 2008 XKR-S, they put a stiffer rear bar on, and left the front one the same. The XKR-S GT also got a different rear bar, no changes on the front...

There was also a camber kit for the rear to make adjustments (rear camber not adjustable from the factory) but damned if I can find the link now (it was a shim kit).

As for tunes, there's so many options out there now from many different tuners... we have several as sponsors/vendors here on the forum...

It's also possible to simply flash the XKR-S tune into an XKR (I've done a few of them now) but what you really need to do first is put the XKR-S center exhaust section in, it has an x-pipe instead of the resonator, it makes quite a difference on it's own.

 

Great info there thanks, do you know if the XKR uses Bilstein Damptronic shockabsorbers?

Thanks

 

The absolutely horrible experience with Michelin Pilot Super Sport. Not only did they have VERY poor performance unless the ambient temperature was 60F or above, but they literally came apart in pieces big as your thumb. Large chunks of tread fell off down to the cord. The tires didn't even have 3000 miles, and hadn't been driven hard. I talked to the Discount Tire I bought them from and the guys told me they warned me, which they did I guess. Softly. "Are you sure?" kind of deal. Anyway, evidently Michelin took a crap a few years ago and now this Discount Tire hates to sell them.
The only GOOD thing Michelin did was return most of my $$$, almost enough to get the Hankook Ventus V12 EVO2 tires that I have now, and which are MUCH better than the MPSS that I had.
It was funny; a fellow in this forum.... Queen and Country..... ragged me for MONTHS about my hate of Michelin. One day he apologized because the Michelin PSS tires he had.......... Fell Apart.
Another funny thing... I left an HONEST review of the Michelin Pilot Super Sport tires on their website, but it was denied as "Doesn't fit our needs at this time." I guess the reason they are rated so high is that most the BAD reviews are discarded. Good Business Practice!

 

[QUOTE=Cambo;1579449]...
There was also a camber kit for the rear to make adjustments (rear camber not adjustable from the factory) but damned if I can find the link now (it was a shim kit)...

Really? I feel a parts-search quest beginning

 

Shims are something like this http://www.aligncraft.com/parts.pdf there was someone on here with an X150 XK who got some shims from another vehicle to fit (a Ford or Lincoln from memory), but damned if I can remember who it was... you also need to shim the brake calipers the same angle as the main shim to get it properly aligned.

EDIT

Or was it from a Volvo? Something from the Ford family I'm sure...

 

[QUOTE=Cambo;1579449]Well there's a few things that are possible...

You can get a stiffer front sway bar https://www.jaguarforums.com/forum/x...ll-bar-167767/ the sway bars on the XK are the same as the XF, XJ, S-Type, F-Type.
/QUOTE]

I'm going to look into that front one!