With all 4 wheels locked together with either limited slip or locking=20 differentials and a hard gear/chain transfer case (drives the other axle=20 wheels), there is a significant improvement in steering and braking. On=20 our Ford Bronco (and most other true 4wd) the front axle drives several=20 percent faster than the rear axle. Even though the front and rear=20 differentials have exactly the same ratios, the transfer case has a=20 chain with slightly different number of teeth. This is standard=20 industrial practice so the chain and sprocket teeth always "hunt" (same=20 teeth don't run on same chain link for many revolutions. With the front=20 pulling slightly faster, stability is significantly better, and can=20 easily drive 65 mph on ice with no stability issues. Yes you can't stop=20 fast like dry pavement, but it will go near straight without wanting to=20 swap ends. The disadvantage is at very low speeds, it wants to go=20 straight, even with the steering all the way one side. On 6/9/2011 7:49 PM, Peter Loron wrote: > On 06/09/2011 10:35 AM, Oli Glaser wrote: > =20 >> On 09/06/2011 18:13, Gordon Downie wrote: >> =20 >>> On Thu, Jun 9, 2011 at 3:20 PM, Michael Watterson = wrote: >>> >>> =20 >>>>> But SUVs have rubbish handling on slippy surfaces. >>>>> 4WD is designed for slowly on a very uneven surface. It needs turn= ed off >>>>> on ice/wet >>>>> =20 >>> Really? 4WD have excellent performance on slippy smooth surfaces. Im >>> not sure if you are just referring to SUV's or all 4WD. >>> Not quite perfectly smooth, but Audi showed how good and fast a 4WD >>> could be on loose gravel in WRC back in the 80's >>> >>> In the UK when is snows, the guys in the Audi quattros have most fun. >>> FWD slow and steady, but easy to get stuck. >>> RWD forget it (Unless you are a very very good driver) >>> =20 >> I wondered about the above too. I have a Mercades G-Wagon (a kind of >> jeep made for German military) >> http://en.wikipedia.org/wiki/Mercedes-Benz_G-Class >> I always use this when it snows or roads are bad (we live in a remote >> country area) as the other 2WD merc we have often hasn't got a chance >> (before we got the G-Wagon we had to just stay home if it snowed badly, >> so it certainly was not purchased to make a fashion statement :-) ) >> The G-Wagon in 4WD mode has never got stuck anywhere, the locking >> differentials help if it's really bad. >> So IME it seems to me as if 4WD works better on ice/snow (and does seem >> to make logical sense as the drive is transferred to the ground more >> evenly), although I'm no expert on this kind of stuff. >> >> =20 > 4WD isn't likely to help you stop or turn on ice, but it can help you > avoid getting stuck. Good winter tires help a lot as well. > > The best tool, of course, the the one between your ears. > > -Pete > =20 --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .