alexg
Part of things
Posts: 550
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Does it make any difference with tyre pressures for driving on ice covered roads. I had a big old hill to make it up yesterday and let half the air out my front tyres (as FWD) as I thought it would help traction. Or is this not the case?
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1979 'V' Austin Allegro Estate
1990 'G' Rover Metro GTI 1.8 VVC
1985 Sinclair C5
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On ice it makes very little difference. On snow lower pressures are theoretically better but most of it gets compacted to ice very quickly. You'd be better off grabbing some chains.
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1997 TVR Chimaera
2009 Westfield Megabusa
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MWF
Posted a lot
Posts: 2,945
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Very hard to say with snow and ice because of all the variables. With snow you ideally want to avoid any floatation and cut through to the hard surface below. With ice you want a large contact patch to try and get more purchase and smooth out ridges.
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As aid above, too many variables: drive format, weight distribution, tread pattern, type of snow/ice etc...
1" of snow is very different to 10" of snow. Ice is a different sport to snow, snow with ice under is different again.
Just drive very carefully and make sure you drive to the conditions.
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Very hard to say with snow and ice because of all the variables. With snow you ideally want to avoid any floatation and cut through to the hard surface below. With ice you want a large contact patch to try and get more purchase and smooth out ridges. Errr, no! With snow you want a wide contact patch to avoid compacting the snow into ice. (think snow shoes) With ice you want narrow tyres to maximise pressure on the road. (think ice skates). |
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1997 TVR Chimaera
2009 Westfield Megabusa
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Tyres on an ice racer:  Tyres on arctic expedition (snow) vehicle:  |
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1997 TVR Chimaera
2009 Westfield Megabusa
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Just do what i did - go out and buy a Delica  |
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1993 Fiat Panda Selecta
2003 Vauxhall Combo 1.7DI van
2006 Mercedes Kompressor Evolution-S AMG SportCoupé
"You think you hate it now, wait til you drive it"
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Just do what I did - go out and buy a Delica Although preferably not one with a dud engine... i cant imagine changing it in -6 to be that fun ;D |
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1997 TVR Chimaera
2009 Westfield Megabusa
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MWF
Posted a lot
Posts: 2,945
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Very hard to say with snow and ice because of all the variables. With snow you ideally want to avoid any floatation and cut through to the hard surface below. With ice you want a large contact patch to try and get more purchase and smooth out ridges. Errr, no! With snow you want a wide contact patch to avoid compacting the snow into ice. (think snow shoes) With ice you want narrow tyres to maximise pressure on the road. (think ice skates). Both wrong, you only want a wide contact patch on snow if you need floatation to stay on the surface. People ArticTrucks use huge floatation tyres because they drive on really deep snow. Ice skates cut into ice, normal road tyres don't. Think about it. |
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Errr, no! With snow you want a wide contact patch to avoid compacting the snow into ice. (think snow shoes) With ice you want narrow tyres to maximise pressure on the road. (think ice skates). Both wrong, you only want a wide contact patch on snow if you need floatation to stay on the surface. People ArticTrucks use huge floatation tyres because they drive on really deep snow. Ice skates cut into ice, normal road tyres don't. Think about it. I've thought about it, so have ice racers and arctic explorers.... Its water on top of the ice that makes it so slippery. Hence you want thin tyres that cut through and clear the water from the surface of the ice, providing more grip. If possible you want to avoid cutting through to ice and stay on top of whatever snow is there as it gives much more traction, hence you want wide tyres with a large contact patch. I'm afraid you have it mixed up |
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1997 TVR Chimaera
2009 Westfield Megabusa
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Whatever you do don't think that just because you can select 4WD it suddenly makes your brakes 1000% better!!! ;D
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If I had two brains I,d still be a halfwit
1969 Morris Minor Traveller
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Lowering tyre pressures makes a noticeable difference to traction in the ice and snow, I know, I've tried it several times.
Our reasonably steep driveway is a mixture of hard packed snow and icy ruts, my car simply doesn't make it to the top without a small reduction in tyre pressure.
Ice racing and arctic adventures are irrelevant - they have cars and tyres fit for purpose (eg. ice racing cars have studded tyres)
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MWF
Posted a lot
Posts: 2,945
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Both wrong, you only want a wide contact patch on snow if you need floatation to stay on the surface. People ArticTrucks use huge floatation tyres because they drive on really deep snow. Ice skates cut into ice, normal road tyres don't. Think about it. I've thought about it, so have ice racers and arctic explorers.... Its water on top of the ice that makes it so slippery. Hence you want thin tyres that cut through and clear the water from the surface of the ice, providing more grip. If possible you want to avoid cutting through to ice and stay on top of whatever snow is there as it gives much more traction, hence you want wide tyres with a large contact patch. I'm afraid you have it mixed up sigh *facepalm* So ice isn't slippery, it's the water on top which is - genuis, And snow adheres to ice - brilliant. This is going beyond stupid to just funny now. *goes off to advertise some wide low profile snow tyres on ebay* |
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Last Edit: Jan 7, 2010 13:19:59 GMT by MWF
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Those exploration vehicles have massive low pressure tyres because they need to sit on the snow and not cut into it,because the snow is that thick the chassis would bottom out.
One the 2-3 inches we get,thinner tyres would be better to push through it down to the road.....less contact patch = more weight per tyre to push through the snow. If there's ice underneath the snow,you need studs. ;D
That's how i see it anyway.
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I've thought about it, so have ice racers and arctic explorers.... Its water on top of the ice that makes it so slippery. Hence you want thin tyres that cut through and clear the water from the surface of the ice, providing more grip. If possible you want to avoid cutting through to ice and stay on top of whatever snow is there as it gives much more traction, hence you want wide tyres with a large contact patch. I'm afraid you have it mixed up sigh *facepalm* So ice isn't slippery, it's the water on top which is - genuis, And snow adheres to ice - brilliant. This is going beyond stupid to just funny now. *goes off to advertise some wide low profile snow tyres on ebay* Wow, i've never seen someone argue common knowledge with such commitment before! Water is a liquid and acts as a lubricant between ice and tyre. Thats something you learn in primary school. Water expands to form ice, when you compress it it returns to water therefore greater the surface are of ice you compress and the more water you have to clear. Surely thats simple physics? - EDIT much like on standing water, skinnier tyres are better than wide ones. Snow compresses into itself and therefore doesnt turn back into water as easily, therefore you maintain more grip by having a large surface area. 2-3 inches of snow compresses to ice as soon as you drive on it unless you have mile wide tyres as it cant compress into itself, therefore skinny tyres will be better. You aren't cutting through the snow though, merely combatting the effects of it having turned to ice. EDIT - it doesnt really turn back to 'ice' as when water freezez, but it compresses to a point where it starts to form a layer of water on top. And for our next debate, MWF will be arguing that snow is infact black... ;D |
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Last Edit: Jan 7, 2010 13:56:14 GMT by Adam
1997 TVR Chimaera
2009 Westfield Megabusa
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LowStandards
Club Retro Rides Member
Bigging Up The Sum Sum Man Since '99
Posts: 2,650 
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Thin tyres are best in snow, trust me, wide tyres skate about on top of it! I have both, all very much tested this last week!
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Thin tyres are best in snow Agreed, I have quite a bit of experience driving in snow, thin tyres are best. (At least in the type of snow we get in this country.) |
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Last Edit: Jan 7, 2010 14:04:39 GMT by skinley
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spacesavers ftw! knew they would come in handy for something oneday
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1984 gtm coupe
1979 mini clubman estate pickup
1990 mini racing green
1996 mini sprite
1992 maestro 500 van
1995 fiat cinquecento
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As I said, in practice the amount of snow we get here compacts to ice with a single passing of a car and is ice before you come to drive on it, hence thin tyres will be better. Very definitely not because of the reason given by MWF that is 'cuts through the snow' however....
And you very definitely do not want a large contact patch on ice as he also seems to claim...! Thats why you see all these Mercs and BMWs with wide tyres stuck on hills etc...
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1997 TVR Chimaera
2009 Westfield Megabusa
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And little old me with me 145s getting up hills when others cant.
The biggest variable that effects wether or not you crash in snow or ice is the one behind the wheel. Sharp stearing acceleration or braking will all induce a skid the best bet is to get in a high gear and just let the car pull itself through although low gears going down hills is a good idea. Always try and change gear on the level so as to either not lose momentum or have to brake. If all else fails buy a DAF hehehe.
The automatic clutch means it pulls away very smoothly from very low revs and the CVT transmission pulls you away in the highest possible ratio providing light throttle is used. Friction belt drive also provides effective engine braking as well as manifold pressure being used to assist in ratio selection. As a result of all these factors I have been using the DAF rather than the modern and its got me to places where some 4x4s would falter. If you want more proof that CVT is the way to go on ice then just look at the fact that all snowmobiles use a Variomatic style transmission.
Paul
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