On 28/11/2010 13:56, Vernon wrote:


Most modern 4x4 have fat tyres, which are absolutely useless in
snowy/icy conditions, older landrovers had skinny tyres. Same with cars,
BMW etc have fat tyres, small supermini tend to have thin. You only need
to look at the news, BMW etc struggling to make progress, passed by a
fiat panda or such like.

I wouldn't have called the crossply remoulds I had on my 2A SWB LR
skinny. They did have a much better tread for mud and snow than the
radials I had on my later Ranger Rover.

BMWs struggle in snow for the very reasons that make them such nice cars
to drive for most of the year - rear wheel drive and near 50/50 weight
distribution. Front wheel drive gives a very significant advantage when
it is really slippy (pull not push) as does loading the driven wheels
with 70% or more of overall weight.

Skinny tyres allow the car to make better progress as there is more
weight per square inch on the road. Combined with knobbly tyres on a 4x4
or snow chains on a car, means you can make the most of what grip is
available, obviously a 4wd sends less power to each wheel so it is
easier to get traction and move off. That might explain why you could
not get up the hill, as you could not get enough traction. Snow chains
might have helped, as would winter tyres.

Fat tyres per se make next to no difference. With radials the tyre
footprint is very much determined by the tyre pressure, not the tyre
width, other things being equal.

Some time ago, top gear did a test of 4x4s to see how far they would go
across a grass field with a bit of a slope, they all got stuck, the
Range Rover got the furthest, but the farmers old series 3 land rover
with the right tyres drove past the lot of them.

Down to tyres. Modern road tyres clog with mud very easily and once that
happens you effectively have slick tyres.