I have a 2008 XJR. Admittedly I have terrible snow tires (Bridgestone Potenza RE 970 AS Pole Position, the all-season tire for the tropics). Since 1961 I have had several cars with limited-slip differentials. And innumerable makes and models of tires ranging from summer dry pavement only to M&S.

Last night I was out in a snow squall with .5 - 1" of snow in 20 minutes and drove back streets for about 90 minutes afterward. I turned off stability control so I could actually drive up and down hills using the throttle and light spin when needed to cut through the fresh snow to the under laying surface. I have been out on many occasions where I switched SC on and off for the best results in the circumstances of the moment. Which is usually OFF.

I recently looked at some material for Jaguars new AWD models. No mention of slip limiting other than references to their stability control.

To Jaguar: Your Stability Control is very inferior to a decent limited-slip differential in Michigan snow and ice. Since you think you are serious about cars meant to be driven do it right.

 

Thx for this experience sharing.
I'm puzzled. I thought SC was there exactly to keep track when one wheel may lose grip...but I understand from you that SC actually may instead block the remaining wheel, correct?

 

The problem is with SC shutting down the throttle and not allowing any wheel to spin and bite through the snow.

SC can be dangerous. On more than one occasion I was accelerating briskly and hit a short slippery space and the throttle was shut down and slow to be restored after I was on good traction again.

One example was going down a freeway ramp in moderate weather where there probably was an oil patch and I end up entering the freeway at about 40 mph with 70 mph traffic very close behind me. Not good. If throttle recovery with the throttle floored had not happened at that instance very bad things might have happened.

I have had many occasions where SC did just the right thing. But also many occasions when it did the wrong thing. The first year or two I had the car I used it almost all the time. But for the last year or two I usually drive without it.

I always drive in Sport mode. It might be my imagination but it seems to me that throttle response in normal driving is just a bit quicker and sharper with SC disabled.

A final note: SC is based on the idea that something has traction. Wet ice or black ice can make any tire, ABS, or DSC useless. I hate those, fortunately very rare for me, moments.

 

I agree.

My (oldie) XJR has both traction control and a limited slip diff (thank you, Jaguar) . I generally like the traction control but I almost always have to turn it off when driving in snow.

The limited slip is a help in snow. The traction control is a hinderance.

Cheers
DD

 

Been tooling around here in snow several times in the last few weeks and understand that getting around is more a matter of technique than brute force.


My tires - Yokohama YK580 from Discount Tire - are fair at best in the snow, but do very well under most other conditions. As a result, I do get a lot of wheel spin and SC intervention. Being respectful of tire life, I haven't even considered turning SC off.


What I have noticed that you might confirm is that there appears to be many variables under observation with the CATS. I have noticed, for example, that steering wheel position profoundly affects what the back wheels are trying to do. Crank the wheel in the direction of the skid and oversteer is served. Crank back to center and everything settles almost immediately back down, even if you're still going sideways. So, what I have learned to do is let the backend swing a little wide and when I'm ready to knock off the acrobatics, a quick jab back toward center and the car drops back in line.


None of this, however, gets you launched more quickly. Wheel slipping will still crank back the throttle and have the rear brakes chattering to reel in the low-traction side. Launch then with these wide Yokohama sneakers remains an exercise in looking for grip.

 

hear! hear!

A '73 Firebird 455SD on belted summer Firestone F60-15 could make it through a foot of snow with confidence. It had a 10 bolt rear with LSD.

 

So what do you think is going to happen to these autonomous vehicles when they encounter snow for the first time? I suspect that, just like modern trains, they will say it's the "wrong kind of snow" and shut down.

Chris

 

No 'all season' tire is worth squat on snow. Don't blame the car.

 

Wrong. Over a half-century I have used Pirelli and Michelin winter tires, and many kinds of tires classified as all-season. Some of the all-season tires were quite decent in winter but not nearly as good as M+S tires.

Being retired I seldom have to drive on snow and ice. From my house to and from anywhere is down one small curving hill and up another of the same, and yet another steeper small hill. If I were still working I would definitely get something AWD (probably MB E or S series). And look for much better all-season tires than what I now have.

 

OK, so blame the particular shi**y four seasons tires you've got. Still not the car's fault.

 

Actually the traction and stability control kicks in too early in an 2003+ jags. even with decent winter tyres sometimes it's hard to drive in a snow w/o turning off a SC. On an previous XJ (i mean x308) TC and SC worked like a charm and there were no problems in a winter driving even with all-season tyres.

 

If so, does anybody know whether that can be tuned via the IDS/SDD?

 

There's no way to tune it.

 

I noticed that the latest XJ or XF has an Ice/Snow button on the centre console ...

 

When a winter mode is active car always starts from a 2nd gear and the throttle body response is some kind slower, so there's less risk of tire spin. Anyway, it is not helpful sometimes.

 

I'm not familiar with the idea that wheelspin on snow and ice is "good" because it cuts through the snow.

I have however seen people spinning their wheels until they sink into deep ruts they've created.

What depth of snow does your spinning technique work on?

 

When driving on an ice - sometimes it is impossible to launch the car at all, while a TC is active.
During a snow driving a controlled wheelspin helps a tyre to clean a running threads from snow, while an engaged TC prevents it.

 

This winter's must be very difficult on those in the south not prepared for such weather. Up here in the Great White North where snow and ice are a weekly occurrence, we are expecting 50cm (1.5 feet) of mixed snow and freezing rain over the next 48 hours. I average 50,000km per year on my company car and another 30,000 on my personal vehicle so I have an abundance of winter driving experience. Well here is my list.
1. The XK8 stays in the garage November 1st through May 1st.
2. All season tires are useless in all seasons. if you experience snow and ice on a regular basis, purchase dedicated winter tires, they are made of a softer compound and give greater traction not only on snow and ice but in the cold also. I use Bridgestone Blizzacks and have great luck with them. I can't stand the noise of studs but my wife swears by them. and to be honest after the last ice storm she got up the driveway and I didn't.
3. Traction Control off if the snow is more than 10 cm (4 inches) deep. The wheel spin is necessary to maintain speed. The TC slows the vehicle to a crawl on all 3 vehicles allowing snow to build up and eventually getting stuck.
4. Carry a small bag of sand in the trunk, not for weight but to spread on the ice when stuck.
5. Remember if you can't walk on it you shouldn't be driving on it either!
6. If the local constabulary advises against driving, heed the warning. Pour yourself 2 fingers of Single Malt, and watch reruns of Top Gear on Netflix.

that's my nickels worth, Canada eliminated the penny so 2 cents isn't possible.

 

1. The road is gravel or paved but not covered with ice.
2. Powder or medium density new snow. Less than 3" with my current car.

These conditions usually happen when it is very cold and the snow does not pack very well. If it is near freezing the snow packs down and I am screwed.

Previously I had a 4500 lb. Infinity Q45. While that cars specs do not mention a limited-slip differential it unmistakably drove like one. It had ABS but not DSC. With Michelin Pilot Alpine Sport (or something like that) winter tires it was much, much better in snow than my Jag. Unfortunately that model tires are, or were when I last checked, not available in my Jag's size.

 

Ah, I see. Round here the snow temperature usually hovers around freezing, so it will be soft slushy snow in daytime, or refrozen to hard and glassy overnight.