Being that this is a new feature to me and I have a basic understanding how it works can someone tell me if it being on or off would affect normal driving. Does it function during what I would consider normal highway/city driving where you would be taking some spirited turns but not getting deep into the go peddle. Does it also affect mpg if turned off or left on. Do I assume that those who take a once in a while track day turn it off or do you leave it on. Just trying to learn a little more on the function from a practical viewpoint. Thanks

 

It "probably" won't activate even in spirited driving but I suppose it could do (hit a patch of diesel or whatever). Shouldn't affect MPG. It may well activate if you try to pull away fast on (say) gravel. I test it that way when no other cars are about.

I've only turned mine off when desperate, in snow, at very low speed.

 

I see traction control activate most times when I drive in the wet - unless I'm gentle on the gas pedal from a standing start, the rear wheels will break traction and DSC will cut in. Mind you, I do like to play "traffic light Grand Prix", so I may be a little more enthusiastic than some other XKR drivers. But the 5.0 XKR has more torque than it has traction, so it is pretty easy to spin the wheels. I don't tend to experience it when cornering, because I'm fairly progressive feeding in the power.

I leave DSC on for road driving - the last thing I want is for the back end to step out when there are other cars, crash barriers, etc. to whack into. For track driving, I switch to TracDSC; that gives me more leeway, but will still save me if there is oil or water on the track that I haven't seen. Perhaps if I become more confident with my ability to control the car in high-speed oversteer, I might switch DSC off completely, but I'm not brave enough for that yet.

 

Hmmm, how do you switch to "track DSC" ?

For spirited driving in the 5.0 it definitely kicks in on the street. Turns, loose gravel, water, etc. with the tourque monster all give the car's electronics a good workout. The 4.2 is probably not far behind since it is far from lacking in the torque arena even if not at the level of the 5.0.

 

Press the DSC button for less than 10 sec and you will see the instrument display trac DSC. If you hold it for longer you will see DSC off.

 

Mine had hard tyres when I got it, so the wheels would spin virtually every time it kicked into second, especially in the wet. New tyres on the back and it is much improved. But on the track, even with track DSC the light was on more than it was off, but that was a small track with lots of corners and an ordinary driver.

 

When I first got my 2011 XKR 175 in December, 2012. I'll never forget the day--my first Jaguar. With the stock Dunlop tires in the cold Canadian weather the rear end would break loss constantly. I, also, was not familiar to driving high performance cars with so much torque. I find the Pirelli tires on my 2013 grip a bit better. I also have gained much more respect for the performance of the car. If I have my car long enough I will replace my tires with Michelin PSS's and go to bit wider.


In cold weather you will find the DSC engaging more often.

 

Yeah, my next rear boots will be MPSS 305/30, an increase of 10mm over the 295s which are standard on the 75 and R-S - I presume (with the Dynamic Pack) you also have 10.5" Vulcans?

 

The DSC kicks in anytime the tires break traction, this includes trying to pass someone under heavy acceleration, or accelerating and running over a slick spot on the pavement. It also helps in controlling the direction of the vehicle in extreme conditions via the E-Diff and torque vectoring.

Mine kicks in a lot on the street and as DGL mentioned the stock Dunlops would kick in DSC pulling out of a parking space.

TRAC DSC makes it a little harder to engage the DSC as it allows slightly more wheel spin but not to much. What I've noticed on the track is it kicks in hard when slip angles are exceeded, which shouldn't happen on a street unless you hydroplane or are about to have an accident. If I go into a turn a bit too hot or am trying to balance the car around a long corner you can hear the rear brakes kick in and slow the car as its exceeded the slip angle. It gets very annoying when exiting a turn aggressively as the slightest wheel spin will kill the power way too much.

For the non racing guys the slip angle is the angle of the wheel vs the angle the wheel/tire is actually going. I doubt they are measuring actual slip angle but the amount the steering wheel is turned vs direction/speed the car is turning.

On a track you try to shoot for a theoretical(depends on a few factors) angle of 6-7 degrees to be efficient. If this is passed you are either in a pushing the car hard or in a understeer situation so the car slows itself via DSC braking so the front tires can regain traction and an optimum(according to Jag) slip angle. So basically you don't drive into whatever your steering away from.

The E-Diff which is part of our DCS system as well, that features torque vectoring via the brakes which is what is tries to help you stay on course.

On the street I leave it on full mode all the time as its saved my butt a few times. Not that I was doing anything dangerous but with all the distractions we have driving, throw in ~500HP-600HP, traffic, and a slick spot (which may just be patching) and it will save you from facing the wrong way on a road or at least get your attention.

 

My Traction Control light would come on all the time, especially in the wet, even more so when the tires were pretty worn. Works well I must say and I see no reason to turn it off. I wanted to get squirrely in my VDP and shut it off; big mistake. I wasn't use to driving an automatic and thought I could spin the back out around a corner; not so much and $700 at the body shop later.

Lesson learned; leave it on. I can see on a track, turning it off, but for regular driving, just leave it on. It doesn't impede much in IMO.

 

On the road its always on, there is no benefit to turning it off. Unless you feel like being a hooligan

 

Yes. It has the Vulcan wheels with the wider Pirelli tires, included with the dynamic pack option.

 

I hope they are still available!!

Loth

 

The MPSS 305s seem to be available over here; at least, they're listed on some of the online dealers.

 

Yeah tirerack.com has them.. do you guys have the 255 fronts? They are listed as backorder over there. Anyone switched to 265 fronts???

 

Yup, £234 for MPSS 255/35/20 from blackcircles.com.

One of the R-S owners put 265 fronts as well as 305 rears on his, and reported no clearance issues at either end. I may do the same, but both of my fronts have a fair bit of life in them, so that's not likely to happen soon.

 

Are the 265 fronts the 265/35/20 or 265/30/20?

 

You need to keep the 35 profile of the stock 255s; going to 265/35 only increases the rolling diameter by 1%, whereas going to 265/30 reduces it by 2.8% (and probably makes the ride a bit harder). There's a very handy calculator here:

Visual Tyre Size Calculator | Kouki Tech

Since the 305/30 rears are 0.9% larger than the 295/30s, 265/35 fronts give a balanced increase front & rear.