How to be an idiot.

[Mej]

my bmw is sh*te in the snow, 18" 255 Pilots are rubbish, i cant get any grip at all, just slide everywhere, but then in the summer they are awesome!

this weather kind of makes me want a 4wd, audi or something but we just dont get it often enough down here!

[Mej]

Originally Posted by fizzwheel

Also IIRC the tyre is cut differently has bigger blocks that move around so that the snow / ice gets squeezed out of the tyre so it doesnt get clogged up / become a slick.

I think...

also a problem i have!

[fizzwheel]

Originally Posted by Mej

this weather kind of makes me want a 4wd, audi or something but we just dont get it often enough down here!

You'll have the same problem with a Quattro if its fitted with big ass sports tyres, its the tyres causing the problem not the lack of 4WD.

Originally Posted by fizzwheel

Thats how I understood it, the tyre has a higher silica / rubber content, which means it works better when the temperature is colder. Also IIRC the tyre is cut differently has bigger blocks that move around so that the snow / ice gets squeezed out of the tyre so it doesnt get clogged up / become a slick.

I think...

Mrs Owenskis folks live on the France/Swiss boarder where its a legal requirement to fit winter tyres after a certain time in the year (invalidates insurance to be found not using them). They're winter tyres look sort of knobbly by comparrison to their summer ones. IIRC they had 3 monsterous channels in then hoizontal groves of similar width at staggered intervals, sort of like a chain of "E" shaped grooves. We drove up into the alps without a problem, he drove pretty much as you would on any normal road in normal conditions but it did have the advantage of also been an Audi S6 estate.
They're actually making their way up for christmas, they were intending to fly but with weather been what is has they've decided to make a trip out of it and drive the whole way, so once they're over here they'll be putting most cars here to shame.

The other reason most 4WD are less effective nowadays, is that few of them have diff lock, so all the power gets sent to the tyre with the least grip, and many are part time 4WD only send power to the back when slip is detected at the front. Regardless of tyres, with four tyres rotating together at a constant speed, such as you can have in a Land Rover Defender, you would have 4 times the traction of a 2WD car with one spinning wheel.

[Luckypants]

Originally Posted by fizzwheel

Thats how I understood it, the tyre has a higher silica / rubber content, which means it works better when the temperature is colder. Also IIRC the tyre is cut differently has bigger blocks that move around so that the snow / ice gets squeezed out of the tyre so it doesnt get clogged up / become a slick.

I think...

You are confusing WINTER tyres and SNOW tyres fizz. Winter tyres like you say are softer / higher silica with lower operating temps to provide better grip in the cold when 'normal' (aka summer tyres) struggle due to going hard. The tread patterns tend to look 'normal' on these tyres as they are designed to shift mainly water. Snow tyres will often have the above low operating temp features but with the bigger blocks you refer to, with sharp edges and bigger channels to bite into the snow and some flex to help clear the snow from the tread.

My tyres are a certified snow tyre (in N. America) so count for insurance purposes in areas where snow tyres are required. However, I'd not consider them a winter tyre as the compound is not especially soft (in fact quite hard wearing) and seems to be designed for year round use. So I get good grip in snow but would be wary of ice.

[Luckypants]

Originally Posted by -Ralph-

The other reason most 4WD are less effective nowadays, is that few of them have diff lock, so all the power gets sent to the tyre with the least grip,

Rather depends on which diff you are talking about. Most basic 4WD systems don't have a centre diff, so that is 'locked' by default. So you need to spin a wheel on both axles to lose all traction. Then some cars will have a lockable centre diff like the Defender you refer to and my x-trail. Very few standard vehicles have come with lockable axle diffs, as they are rarely needed with a locked/no centre diff.

There are also cars with clever electronics that detect wheel slip and brake the spinning wheel (latest non-defender LR models), which makes the use of diff-locks unnecessary...

The latest 4WD systems are still very effective, but it helps that the drivers RTFM and understand what they read.

[Stu]

Originally Posted by Luckypants

You are confusing WINTER tyres and SNOW tyres fizz.

Not Bleedin' surprising! considering the rubbish information being bandied about in the media.
We've had the Transport Secretary say in the house that winter tyres would not be beneficial in this country.
http://www.tyresafe.org/news-and-eve...,2LSNO9,WM0G,1
Which outraged the tyre industry.

Also see
http://www.youtube.com/watch?v=FKEdK...,2LSNO9,WLWB,1

Actually I can't see Tyresafe diferentiate between Winter & snow tyres and the 1st link claims that winter tyres stop "11 metres sooner on ice and eight metres sooner on snow, from just 20mph. "

The other day the news had a report from Finland about studded tyres that they use in their -25 degree roads covered in snow with no grit. I thought that was completely irrelevant to our situation

[fizzwheel]

Originally Posted by Luckypants

You are confusing WINTER tyres and SNOW tyres fizz.

I thought I might have been

I have finally got our Audi home, I had to shovel off my mates drive, despite it being a very slight incline the damn thing wouldnt get up it. Got up it after some shovelling and removing the hard compacted snow. I got it up our road OK and its now sat in front of our house. Turning the traction control off on it helps alot, but its still bl**dy useless where the snow has become compacted.

I'm seriously thinking about getting a pair of these for it and leaving them in the boot

http://www.autosock.co.uk/

[Sid Squid]

Originally Posted by Luckypants

Most basic 4WD systems don't have a centre diff, so that is 'locked' by default.

Are you sure? This surprises me somewhat, all the 4WD vehicles I have worked on have a centre diff, I imagine a road car would be unusable without a centre diff, the steering would be extremely heavy and the wear on transmission and tyres would be very high. Also on all 4WDs I know of there are warnings not to lock the cntre diff when on the road or even in the rough if the grip is good.
Certainly the Landys etc have only a centre diff that's lockable, but unless the circumstance is extreme this will still mean that two of the four will be driven whatever's happening at the other end of the vehicle.