durangotang wrote:
icarl wrote:
HoppedUpOnGoofballs wrote:
Actually, unless you are stuck the tire does not cut through the snow it compresses it. You have to think in terms of tire footprint and not just tire width. The footprint size depends on tire width, diameter, and tire pressure. A larger footprint will produce less compressive force and 'float' more on top of the snow. A smaller footprint will do the opposite. More compressive force is good in many loose snowy road conditions. On pure ice or hard pack it makes more sense to have a larger footprint since the base is already compressed. A larger foot print has more biting surfaces.
Sorry but this is wrong... a larger footprint does not provide a better "biting surface". The truth is quite the opposite actually. A narrower tire provides more pounds per square inch of pressure on the ice (which is the only way of creating friction on ice). Pounds per square inch is the reason an ice pick sticks better than a sledge hammer in the slick stuff. The reason why you get better traction on the snow than the underlying ice is quite simple: snow crystals are very abrasive and create a lot of friction when they are sandwiched between your tire and the ice. A narrower tire will also apply more pressure between the snow crystals and the road. This gives us traction that we can use. Things change when the snow begins to get deeper and creates drag. As it gets deeper you start to fight drag on the undercarriage and the efforts of the leading edge of the tire to "climb" through the snow in front of it. You will spin when the drag exceeds your traction. This is when you consider increasing flotation to decrease the drag as opposed to increasing traction. Driving through deep snow is treated the same as driving through sand... driving on ice is a different animal entirely.
Long story short: narrow tires on ice---> good
(so says the guy who has driven thousands of miles above the arctic circle)
I did not say a larger footprint has a better biting surface i said it has more biting surfaces spread over a larger area. Yes higher pressure will produce greater friction. However when you create higher pressure you also reduce frictional area so the amount you gain from pressure you lose from a loss of area. IMHO if the ice that you are driving on is uniform then it makes no difference if you use a skinny tire or a wider tire. The reason for this is friction is directly proportional to surface area, weight, and the coefficient of friction of the surface. If you increase the surface area this increases the friction. Likewise, if you increase the weight this also increases the friction. So if you vary tire width you lose/gain area and pressure, but the net friction is the same. It's 6 of 1 and half a dozen of the other. However, if the ice is not uniform having a larger footprint will give your tire more opportunity to find traction.
Also you need to consider why racing cars use fat tires because they provide more frictional surface area to the road. If pressure were the only factor then they would be using skinny tires on race cars.
The reason a blade works well on ice is because it cuts the surface and digs into the ice. tires can not do this because they are blunt and not sharp, unless they have studs of course.
In all honesty it is more complicated then what we have talked about here and we both have valid points to our arguments. For example, A tire's contact patch is always changing therefore the maximum coefficient of friction can occur anywhere within that contact patch. A wider tire has an advantage in that the greater the area, the greater the likelihood of maximum traction. Thus, under identical load and on the same surface, the wider tire has a greater contact area and develops higher traction, resulting in greater stopping ability.
here is an interesting read on narrow/wide tires
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