Why do snow tires have to be narower?
I know it makes sense when you compare two tires in snow and decide a narrower tire has to "plow" through less space than a wide tire. But I am wondering isn't it the grip that is more important rather then the force to push snow to each side of the tire?
1st example in medium snow: wouldn't a 225/50- snow tire that is brand new and has tons of crevices and little nooks for snow to grab onto be much better than a narrow 205/50- snow tire? That is 2 cm of extra space with room for a tire to grip to snow.
2nd example on very thin snow and ice: wouldn't a thin tire (i.e 195/50 - or bicycle tire) just slide extremely bad left and right on light snow and ice versus a thick tire? That is more room and more space on a tire for it to grab on to pavement, road, etc.
Remember I said medium (under 8-12 inches) and light snow ice (1 inch or less) not heavy (over 8-12 inches). Thank you.
Answers & Comments
Verified answer
A narrower tire exerts greater ground pressure than a wide one. Put another way, a wider tire will have a greater tendency to float on top of the slipper stuff rather than digging in to it where it can get the most traction.
They don't, but it does help.
It will meet less resistance in going through the snow and provide better directionality. The traction (tangential) force depends mostly on the rolling radius.
Consider that it is about the pressure force per unit of surface (lb/sq in) - the smaller the surface, the higher the vertical force, making it easier to cut through snow.
In your example #1 the extra 2 cm increase the contact surface and lower the pressure - the car will float rather than cut the snow. That is good and desirable in a track vehicle (a tank), not in a car.
Example #2 matches car and bicycle tires, a rather inappropriate comparison. Ice is a different story and in some conditions it may help to have sufficient contact surface, which most car tires have. As for bicycles, you'd have to provide proper car-like load and suspensions (impossible) to study their behavior.
It is hard to provide clear-cut solutions since many other factors influence the snow and ice traction - weight distribution, suspension, wheel torque, engine/drive layout.
As for the snow depth, 12 in will make most sports cars slide on their bellies and loose most of their snow maneuverability due to the effect, which is why they are better avoided in very snowy climates.
For best winter equipment and techniques check out what and Swedes and Finns do and try to follow.
A wider tire causes more resistance against the snow thus causing a decrease in traction. A narrower tire has less resistance and can literally slice through the snow.
Narrow tire cuts into the snow whereas wider tire will float on top of the snow. Opposite true if you are in the sand. Look at the Highway Patrol SUV, they have narrow tires.
So it looks like everyone says a narrower tire would dig down and do better. Well I beg to differ. You are riding on snow and ice the tire will never see the road surface will it? So for me the pushing through is a problem for the engine and the bigger the bite the better the traction and if you want to go on ice you will need every bit of tire you can get to do it. Does that clear things up for you?
It applies more lbs per square inch to the road surface as well. It cuts down through the snow easier. The wider the tire, the more likely it is to sit on the surface.