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Date:         Sun, 26 Dec 1999 10:02:51 -0500
Reply-To:     Alan Pickersgill <pickersgill@HOME.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Alan Pickersgill <pickersgill@HOME.COM>
Subject:      Re: More counter-intuition re traction (some token VW content)
Comments: To: Dominique Cormann <kozmik@home.com>
In-Reply-To:  <3865CF902B3.5BD3KOZMIK@mail.glph1.on.wave.home.com>
Content-Type: text/plain; charset="us-ascii"

I think the unnamed racing driver was probably making the point that front wheel drive cars, although they often have superior traction for getting going, can be much trickier to drive when they reach the limit of adhesion. This gets still trickier if the front has much better grip than the rear. As Judith/Leo say it is essentially a question of understeer and oversteer, but I would argue that it isn't strictly a question of preference, because often you'll get both, one after the other within the same incident. Even the best balanced of the front drive cars, when they get on a slippery surface such as ice, tend first to understeer (refuse to turn in and plow). Then, sometimes, comes the oversteer.

Imagine approaching a turn and begin to turn, but the car doesn't respond, refuses to turn in. You turn the wheel more, it still refuses to turn. Sometimes it'll just go straight on and if you're lucky no one is coming the other way and if you're luckier there is a nice soft snowbank and you go straight in. A little shovelling and off you go.

An alternative scenario - starts the same way refusing to turn in. The average driver will now get scared and lift off the throttle, this will make things worse breaking any little grip there may be. Worse still they may apply the brake causing loss of adhesion at all four corners. Then suddenly the front tires find grip (bare pavement or salted/sanded surface) and the front wheels do turn in; the wheels are usually turned in an exaggerated way by now. Rear end, still on the slippier surface comes around very suddenly (violent oversteer) now you're sliding sideways to the road. If you're very very quick and you know what you're doing you may have a choice - let it spin or try to catch it by counter steering (turning the wheel the other way). But even talented race drivers, who know what to expect, often don't catch it. And if they do it probably isn't over because the same thing will now happen in the opposite direction, and if they don't spin this time it may happen a third time (a tank slapper). Providing the rear wheels with as much grip as possible on front drive cars reduces this tendency to sudden oversteer.

Although I haven't heard of anyone actually suggesting snows on the rear only, it is common and well founded advice to put on 4 snows or nothing or put the best two of four on the rear. In my view front wheel drive is a blessing and a curse. It's much easier to get unstuck and is more forgiving of "minor" driver error than many rear drive cars, although not than the best. However once you've truly gone beyond the limit of adhesion, it is hard to get it back, things happen suddenly and violently. I'm with Judith and Leo, I'd rather have the predictability of progressive oversteer any time. I think it's one of the reasons that many true enthusiasts love BMW cars, and although Porsche's are famous for the oversteer being sudden and unpredictable too, it isn't like a front drive car. MHO.

Now the Vanagon can be fun with gobs of oversteer on a really slippery surface like ice, but you want to make sure you don't encounter sudden grip or you could get onto the roof.

Alan Pickersgill Ottawa Ontario Canada

At 03:19 AM 26/12/99 -0500, Dominique Cormann wrote: >On Sun, 26 Dec 1999 01:40:08 -0500 >Judith Barr/Leo Girard <lgirard@BMTS.COM> wrote: > >> Hi all, >> I have been interested in the discussion re tire width & traction. It >> reminded me of another counter-intuitive statement I read about two years >> ago re snow tires on front wheel drive vehicles. >> This was attributed to a race car driver of some repute (I forget the name >> at the moment). He said if you were to put TWO snows on a front wheel drive >> vehicle they should go on the BACK. Make sense to anyone? > >I've heard this. If you put them on the front, the front gets to much >traction and the rear end flys around oversteering easily. > >People who would rather understeer then oversteer tend to want to put >them on the rear. > >Personally I would rather be able to steer, and I'll deal with the >oversteer, so I'd put them on the front. > >IMHO there isn't a right way to do this, it just depends on which you >dislike more. over or understeer. > >-- >============================================================--------- >Dominique Cormann Email: kozmik@home.com >Homepage: http://kozmik.guelph.on.ca >Diesel page: http://kozmik.guelph.on.ca/gtdproject >84 Rabbit D - daily driver 84 Rabbit GTD - work'in on it > Alan Pickersgill Ottawa, ON Canada


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