Now is the time to buy winter tires. Not tomorrow, not next week and certainly not next month.
The reason for this is that by mid-November, there will be nary a winter tire in the manufacturers’ warehouses. All of the 2010 winter tires will be at dealers and tire distributors. The racks will be empty waiting for next spring’s tires to start trickling in.
WHEELS SPECIAL SECTION: WINTER DRIVING
For the consumer, that means choices in brands and haggling ability over price diminish as the clock ticks. This is especially true if you have a size that is not common. By mid-November, the tire dealer will be telling you what brand you can have and what price you will pay.
When you start shopping for winter tires, arm yourself with some basic information. Start by knowing what your tire size, speed rating and load index numbers are.
This information can be found in a string of letters and numbers on the tire’s sidewall that look like this: P205/55R16 91H. These numbers are important so you get the same size tire and the correct weight-carrying ability that your car requires.
Next, have an idea of the kind of winter driving that concerns you: slush, snow or ice. Do you drive mostly on paved, ploughed roads or do you have to struggle through ankle-deep snow or worse?. There are as many classes of winter tires as there are types of winter boots.
If you can’t remember what boxes you ticked off on the option sheet when you bought your vehicle, take a look for any “sports” or “track” options on the vehicle. Did the sports package include bigger brakes? This may affect your ability to downsize tires for winter.
The classes of winter tires for cars and SUVs can be divided into normal (what the industry likes to call studless) and multi-cell tires. There is a small new category of tires emerging called All-Weather tires, and these may be a consideration for some drivers. Please note that these are not All-Season Tires.
GENERAL PURPOSE WINTER TIRES
For snow traction, a tire needs lots of edges. The sharp edges on the leading edge of the tread blocks cut into snow, so the more tread blocks the better, and irregular shapes of tread blocks are better that squares or rectangles.
Irregular shapes have more edges. Many blocks are good until we get too many of them and the tire becomes unstable at speeds on the highway. That is one of the things that was wrong with the old blocky-tread snow tires of yesteryear.
In addition to many blocks of tread, tires designed for snow will have wide channels between the blocks. This is where snow will be temporarily deposited while the wheel turns. Some will be ejected out the back as the tire rotates, and some may stay in the tread grooves to act as a bonding agent for the next layer of snow.
Some examples of general purpose winter tires that lean towards snow traction are the Firestone WinterForce, Altimax Arctic, BFGoodrich Winter Slalom, Goodyear’s UltraGrip series, Dunlop’s inter Sport series, Hankook Ice Bear, Pirelli Snow Control, and the list just goes on and on.
Tires that specialize in ice traction have an above average count of sipes. Sipes are the little cuts in the tread blocks. They look like superficial cuts that do nothing but when they are touching the road, the car’s weight makes them open up and grab the water off the ice to reduce the lubricating effect between tire rubber and ice. Again, lots of sipes are good, but too many sipes and the tire will squirm because the tread block is unstable.
Tires that lean toward giving extra ice traction are: Dunlop Graspic, Michelin X-Ice and Continental ExtremeWinter Contact.
MULTI-CELL COMPOUND WINTER TIRES
There are only three major players in this high tech, high cost category of specialty tires — Bridgestone, Michelin and Yokohama.
To illustrate the problems with ice traction, hold an ice cube in your bare hands. It will feel very slippery. Now hold an ice cube while wearing a woollen mitten. The ice cube is not slippery anymore, because the wool of the mitt is absorbing the water on its surface.
Since your car cannot wear wool mitts, there has to be some other way to get rid of the water, and it does not take a lot of water to create slip. A few microns of water are all it takes to make ice slick. A micron is one millionth of a metre. We are not taking a lot of water on the ice and, in case the ice is bone dry, the weight of your vehicle on it creates enough pressure to get an instant film of water.
Sipes worked well, but something better was needed. The revelation by tire manufacturers that water on ice was the main problem with winter traction, not the ice itself, led to a major breakthrough in tire design.
In 1988, Bridgestone revolutionized ice grip with the Blizzak winter tire.
The Blizzak was the first tire to use a multi-cell compound; it is essentially a rubber with air pockets in the tread rubber. These millions of “cells” within the rubber are too small to see with the naked eye, but they do a fabulous job of wicking away the water from under the tire’s tread. As the tire rotates, more new cells are exposed, creating an endless stream of little voids where rubber can hide. Well, almost endless. These bubbles are only in the first 60% of the tire’s tread.
Over the years, the Blizzak has evolved from tiny bubbles to irregular shaped tubes. The tire has grown more stable, less squirmy in ride quality. Bridgestone has also added “bite” particles, little microscopic grit particles for more traction.
Yokohama has joined this class of tire with its Ice Guard IG20. It goes the extra mile and encases the bubbles in resin, so the tire is very stable since the air pockets cannot change shape when stressed by cornering.
In addition, they have added absorbent carbon flakes to the rubber. They act like the wool of the mitts above. In the average Ice Guard tire, there are about 1 billion carbon flakes and 5 billion resin coated bubbles.
Michelin has joined this group with the X-Ice Xi2. It features little pockets at the base of the sipes that act like suction cups to get water. They compress, then fill with water before spitting it out after the tire’s rotation clears the ice.
Some other winter tires try to make their sipes do the job of air pockets, but for ultimate grip, it has to be this type of multi-cell compound.
SUV AND LIGHT TRUCK TIRES
Tires for these vehicles are all of the general winter tire type. There are no multi-cell compounds except in a few cases where tire sizes overlap between cars and small crossover SUVs. When you see a tire labeled Blizzak in this class, it carries the branding but does not have the multi-cell rubber. For SUVs look for tires with more siping for ice use and more irregular tread blocks for snow use.
In SUV tires it is very important that the load index be the same or greater than the original equipment tire. Ask about that when you discuss tires. If the salesperson fudges, go somewhere else. Speed ratings can drop for the winter, but load ratings – never.
In this category, you will find many choices; most are skewed toward icy roads. There are no speed-rated multi-cell compounds. If ultimate grip is your goal, you may have to move down several speed rating levels to get a Michelin, Bridgestone or Yokohama multi-cell if they have your size.
Tire companies have winter tires up to V-ratings, but to get that kind of stiffness in a tire you do give up some snow grip.
Often, people choose to downsize tires for winter. The rational is that a narrower tire can get down through snow better than a wider one. There is some merit to that idea, but it has less validity than it used to. There may be a little extra traction down deeper in the snow but, in reality, not much.
Modern winter tires actually use the snow. They compact it in the tread grooves and it then binds to the snow on the ground as the car’s weight creates water. The process is sort of like making a snowball. The tire uses this bond to push itself off the snow on the ground to create forward motion.
The digging down deep theory works best on soft fluffy snow. The downside is a changed shape of contact patch when you are driving on pavement. Downsizing a tire means a narrower tire: a wider tire stops better.
BUYING A PACKAGE
Some tire shops will offer winter tires mounted on new wheels and market them as the “winter package.”
Some offer steel wheels, others offer alloy wheels, depending on the glitz factor of the car. Remember, alloy wheels will corrode after a period of time while steel wheels are ugly. Steel wheels will cost between $65 and $85. Alloy wheels start at $100 and head up from there. Which way you choose to go is up to your personal tastes.
The bigger question is does a package make sense. Generally speaking, the break-even point on the costs of a package versus the twice yearly tire swap is between four and five years. If you plan to keep your car that long, it may be worth considering. If your tires are already mounted on wheels, you will be in and out of the shop in under an hour while you wait. Mounting and dismounting tires is generally a two-hour project.
In closing, let me leave you with a few words of wisdom. The worst winter tire is better than the best all-season tire when the weather gets ugly. The winter tire will stop shorter, turn better and give better gas mileage.
You must use four winter tires. End of story. Using two may get you into a crash far quicker than using four all-seasons.
You should not mix tread patterns. You cannot mix brands or tread patterns in the multi-cell class. These brands all work differently and will not play well together.
If you get a price that is too good to be true, chances are it is. Ask to see the tires and check the date codes to make sure they are fresh. You will have these tires for five years; do not start with tires already a year or more old. This year’s winter tires were manufactured last spring. That is, in 2010.
- Source: Wheels.ca
- Author: John Mahler
- Date Posted: November 3, 2010