Winter drivinng: FWD and RWD with snow tires vs. AWD with all-season tires - what people who have done the tests say

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It seems like every year someone posts a message asking about how to make their 2WD car make it through the snows of winter, how much snow tires help,
and the discussion veers to the supposed benefits of AWD vs. 2WD (front or rear) in such conditions. (Somebody trying to justify their purchase of an SUV, maybe.)
Anyway, so here comes the March 2006 issue of Road & Track, page 71. R&T has done testing of summer tire, all-season tire, and snow tire equipped cars in summer/winter conditions. There opinion is credible. Here is what they say as part of a comparison test of mid-size all-wheel drive sedans:
"Which is better, one of our AWD competitors on all-season tires, or its front- or rear-drive counterparts on dedicated summer or winter rubber? Summer is a close call; but winter isn't. All-wheel drive has its benefits, but not the 28-30 percent offered by dedicated snow tires. And AWD won't help at all when it comes to stopping in snow. Of course, the best choice for winter conditions is all-wheel drive and snow tires."
The 28-30% figure comes from comparison testing of all-season and winter tires on snow - snows are 28-30% better.
I come away pleased from this as it confirms my experience in driving a 2000 Yukon XL AWD with all-seasons and now a '92 LS400 on winter rubber through Michigan winters. I felt the LS was doing every bit as well and even thought it might be doing a wee bit better in all but very deep (say, 10") snow, but the latter seemed counter-intuitive.
Just wanted to make sure this gets into the Google memory banks in time for next winter.
- GRL
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All things being equal 4WD will be better than FWD will be better than RWD and snow tyres will do better than regular road tyres. IMHO essential for any winter driving is ABS, and if you do have a RWD BMW get one with snow mode on the gearbox.
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IME ABS doesn't help when driving on snow or in very slippery conditions.
and if you do have a RWD BMW

My BMW has a snow setting, but I haven't had a chance to try it out yet, but theoretically it should be better with it than without. Mike.
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Mike G wrote:

My experience is contrary to your. In emergency stopping situations the ABS works well in snow or slippery conditions. It can be disconcerting until you get used to how it works, but it does allow the maximum available braking while still maintaining steerage.

Yeah mine does too. It's called 3rd gear (it's a manual trans) ;-)
--
-Fred W

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The problem with ABS in snow or icy conditions, with varying levels of grip, is that it does not allow different braking techniques to be used in line with how much grip there is at any particular moment. At times it may be better to lock the wheels to slow down or stop At other times, it might be better to cadence brake. Varying the rate to give the best result. IMO and experience, basic ABS is not sensitive enough in very slippery conditions. It doesn't give any feel to the brakes. They're either on or off, with virtually nothing in between. I'm not against ABS per se. It's made a good contribution to road safety. I just wish sometimes that I was able to switch it on and off as required in the winter months, without pulling the fuse. Mike.
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Mike G wrote:

It seems to me, and from my experience, the ABS is actually able to react to the varying traction conditions much faster under these conditions than even the most adept human driver. In dry road conditions I think that your analysis may be correct...
--
-Fred W

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My experience tell me the opposite. If there is any grip, ABS is fine, and does react very quickly. It doesn't cope very well if grip is very low, or almost non existant. In such conditions IME, driver controlled braking can be more effective. Mike.
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http://www.edmunds.com/ownership/driving/articles/43810/article.html
It is never better to lock up your brakes on any surface except, maybe, loose gravel where a plow effect can come into play. Lock 'em up on any hard surface and you will increase your braking distance and also loose steering control. A very good driver on the right surface may be able to beat an ABS car's stopping distance by constantly holding the tires on the verge of lock up. But there are few such talented people around.
- grl

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That also can apply when driving on virgin snow.
Lock 'em up on any hard

Agreed. Mike.
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Possibly, but only in deep snow that you are unlikely to be going at any speed in anyway and even then I'll bet you are better off with abs .

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Mike G wrote:

You should try it with good tires sometime. I used to think ABS was a joke, until I ditched the all-seasons...
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dizzy wrote:

Exactly. In that case the ABS was just highlighting the (poor) amount of traction.
--
-Fred W

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The only conditions where ABS iis counter-indicative is deep fresh snow (rare) or pebbles.

From first hand practical experience it is, although an experienced driver with a a manual box wuold do quite well by comparison. OTOH even a top rank rally driver would be likely to better anything but a novice with ABS on wet / icy roads.

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What is "snow mode"? Some kind of automatic tranny thing where the car starts in 2nd gear? I just have traction control on our LS400 and never have any trouble (with snow tires mounted).
I find that the combination of snow tires and traction control on a RWD car (unless it is ridiculously nose heavy, like say an original Hemi-Cuda) results in no worries in any amount of snow that your car can go over and not turn into a plow.
- GRL
R. Mark Clayton wrote:

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Yep.
Yep.
Use the right tool for the job.
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nopcbs wrote:

3rd gear actually.

I prefer to turn traction control off sometimes and use the gas pedal to steer the car at times. Much more fun...
--
-Fred W

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R. Mark Clayton wrote:

Mark, Mark, Mark... we've been through this before.
All things are *never* equal, and that is the real point here.
For one thing, when was the last time you saw a 4WD or AWD vehicle equipped with *real* winter tires? Where I live (Northern New England) people with 4WD or AWD just fit them with all-season tires year round. Why? beats me... but that is exactly what they do. Maybe they figure (like you) that because the AWD provides superior acceleration in the snow they will not need them. Well, as GRL's evidence supports, they are just wrong. Dead wrong. Stupidly dead wrong.
Case in point: It happens to be snowing like gangbusters here today. 10"+ of fresh. The plows (being a Sunday) are not making too much effort to get things cleared up and not too many people are heading out. Probably mostly due to the news reports, stirring up paranoia, etc. Well I needed to get to the pharmacy, so passing up the AWD SUV (It is my boat hauling machine) equipped with all-season tires and I jumped into my E36 325i with the Michelin Arctic Alpins mounted. Needless to say it went through the snow with NO problem whatsoever and I got the required meds. And yes, I feel much better now ;-)
Of course, on the way I passed some fool in the ditch on the side of the road being assisted by the local cops and winched out by a tow truck. Oh yeah... it was one of those cute 4WD mini-SUVs. Want to guess what kind of tires it had on it?
So that is the point that GRL is making, and the same one I have made numerous times before. A RWD BMW with Snow tires is better than ANY other vehicle (FWD, AWD, 4WD, or obviously RWD) with "all-season" tires on it.
--
-Fred W

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I live in England UK, and fortuitously it snows not a lot.

1963 when I lived in Scotland we had maybe -25C & 15cm snow ... worst winter in my lifetime (in UK), but OTOH no 4WD BMW's then.
Maybe us Brits should duck out of discussions of winter driving in the colonies...
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R. Mark Clayton wrote:

perhaps so... less than 6 inches is a "dusting" by our standards in the Northeast. OTOH, it's enough to cripple some of our more southern cities (where incidentally they do not believe in winter tires)
--
-Fred W

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