Originally Posted By: CapriRacer
I would add that I'm of the opinion that tread pattern plays a larger role than tread compound - but it is hardly a point worth arguing over as whatever the tire is made of and whatever tread pattern is on there is unchangeable and sorting out what is causing the improvement in snow traction is a job for the design engineers.
Until thirty years ago, what distinguished snow tires from other tires definitely was the tread pattern. The "M&S" industry standard and certification mark -- adopted in the 1950s and still in effect -- is defined entirely in terms of geometry: land to void ratio, depth of tread grooves, angle of lugs to the direction of rotation, etc. Incidentally, the rubber compounds for snow tires were generally formulated to stay supple at lower temperatures than the tread compounds of other tires.
The open tread, deep groove, design resulted in tires that were noisy and generally hard-riding, and the tread compounds that were optimized for low temperatures got quite soft and wore rapidly in the summer heat, sometimes even throwing off chunks of tread in hot weather. So people who needed snow tires in the winter usually took them off as soon as they could in the late winter or early spring, and did not put them back on again until around Thanksgiving.
The introduction of the "all-season" tire -- IIRC, the first widely sold model was the Pirelli P4 -- was based upon a reformulation of the tread compound, mainly with the addition of a high quantity of silica, so that, unlike the tires that preceded them, snow could stick to the tread. The mechanism by which this gave snow traction was that the snow that stuck to the tread on the first rotation of the tire, on the second and subsequent rotations of the tire compacted with the snow on the ground in the same manner that snow in your hands does when compacted in a snowball, and snow-to-snow adhesion gave snow traction. What was different about "all-season" tires was that, because they did not depend upon the tread pattern for traction, they could be made with tread patterns that are very similar to regular tires, which ran more quietly and had a more supple ride than snow tires.
But the tire engineers have only two ways to give a tire snow traction: mechanical (deep-lug tread pattern) or chemical (hydrophilic tread compounds). While they can use some of both, and twiddle with the balance between mechanical and chemical, as in most aspects of tire design, there is a trade-off. The more the design veers to the mechanical, the noisier and harsher riding is the tire; and the more the design veers toward the chemical, the more water will stay with the tread on wet roads, impairing braking under those conditions.
I would add that I'm of the opinion that tread pattern plays a larger role than tread compound - but it is hardly a point worth arguing over as whatever the tire is made of and whatever tread pattern is on there is unchangeable and sorting out what is causing the improvement in snow traction is a job for the design engineers.
Until thirty years ago, what distinguished snow tires from other tires definitely was the tread pattern. The "M&S" industry standard and certification mark -- adopted in the 1950s and still in effect -- is defined entirely in terms of geometry: land to void ratio, depth of tread grooves, angle of lugs to the direction of rotation, etc. Incidentally, the rubber compounds for snow tires were generally formulated to stay supple at lower temperatures than the tread compounds of other tires.
The open tread, deep groove, design resulted in tires that were noisy and generally hard-riding, and the tread compounds that were optimized for low temperatures got quite soft and wore rapidly in the summer heat, sometimes even throwing off chunks of tread in hot weather. So people who needed snow tires in the winter usually took them off as soon as they could in the late winter or early spring, and did not put them back on again until around Thanksgiving.
The introduction of the "all-season" tire -- IIRC, the first widely sold model was the Pirelli P4 -- was based upon a reformulation of the tread compound, mainly with the addition of a high quantity of silica, so that, unlike the tires that preceded them, snow could stick to the tread. The mechanism by which this gave snow traction was that the snow that stuck to the tread on the first rotation of the tire, on the second and subsequent rotations of the tire compacted with the snow on the ground in the same manner that snow in your hands does when compacted in a snowball, and snow-to-snow adhesion gave snow traction. What was different about "all-season" tires was that, because they did not depend upon the tread pattern for traction, they could be made with tread patterns that are very similar to regular tires, which ran more quietly and had a more supple ride than snow tires.
But the tire engineers have only two ways to give a tire snow traction: mechanical (deep-lug tread pattern) or chemical (hydrophilic tread compounds). While they can use some of both, and twiddle with the balance between mechanical and chemical, as in most aspects of tire design, there is a trade-off. The more the design veers to the mechanical, the noisier and harsher riding is the tire; and the more the design veers toward the chemical, the more water will stay with the tread on wet roads, impairing braking under those conditions.
