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Snow Tire Tech - Traction For The Winter

Posted in How To: Wheels Tires on January 12, 2014
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Because much of the U.S. gets hit with snow and ice in winter, many Jeep owners have winter performance in mind when selecting tires. While traditional snow and ice treads work great on the street, they can leave you stuck in a ditch off-road. There are just as many opinions about what works in snow and ice as there are types of snow that are driven on. This is because what works in one winter situation can fail miserably in another.

On-road ice and snow tires like the Bridgestone Blizzak (bridgestone.com) have many features that you should look for when selecting a snow and ice tire that you plan to use on- and off-road. Dedicated winter-only, street-driven snow tires feature a very soft rubber compound and numerous sipes across the tread area. These tires wear out quick and are not recommended for summer or dry-road use. There will always be a compromise when selecting a snow tread for your Jeep. You have to decide what type of snow and ice you encounter the most.

Winter-specific tires like the Bridgestone Blizzak W965 feature sipes across the entire tread surface, as well as an ultra-soft rubber compound that helps the tires grip ice and packed snow. Tires like this should only be used in winter since the soft rubber compound will wear out quickly on warm, dry pavement.

Mud- Terrain vs. All-Terrain
Luggy mud tires generally perform the worst on ice because they lack many gripping edges and sipes. The large mud tire lugs are designed to move material. They grab the terrain (mud, dirt, sand, snow, and so on) and move it behind and to the sides of the vehicle as it pulls forward. This isn’t a problem in a few inches of snow, because eventually the mud tire will dig down to something solid that isn’t ice. In deep snow, a mud tire will typically dig four holes that will cause your Jeep to get stuck. An all-terrain tire generally has more biting edges and sipes, providing improved traction on ice and shallow snow. They are also less likely to dig in when driven over deep snow. You might think that this makes the all-terrain tire the right choice for snow. Unfortunately, it’s difficult to predict what is under the snow if you dig down to terra firma. It could be packed snow or worse, ice, where a mud-terrain would certainly be the wrong choice. Or, it could be deep mud, where an all-terrain will be virtually worthless. For deep, soft snow-drift bashing, we have had better luck with mud-terrain tires. Mud tires can move a lot of material quickly when attacking a snow drift, sometimes this helps pave a path for those behind you. Some people believe that snow-on-snow provides better traction than rubber on snow in some conditions. To achieve this, you need a tire that that doesn’t eject the snow from the tread like a mud tire is designed to do. For all of these reasons, you really need to consider the winter conditions you plan to encounter prior to choosing a mud-terrain or all-terrain tire for your Jeep’s winter feet.

The more sipes a tire has, the better it will work in the snow and ice. All-terrain tires will generally outperform mud-specific tires in the white stuff. However, there are exceptions. When bashing through deep drifts, the luggy mud tires can disperse a lot of material, sometimes clearing a path when the going gets tough.

Siping
Any tire you consider for snow or ice use should have lots of siping. Sipes are small cuts manufactured horizontally into the tire tread. These sipes open up and grip the snow and ice as the tires roll over the terrain. They provide many more gripping edges than a tire without sipes. Most snowy-area tire stores can add sipes to nearly any tire. This allows those that require the open-lug performance of a mud tire to still get decent performance in snow and ice. As an added benefit, the sipes make the tread surface, and ultimately the tire carcass, more compliant. So, it can envelop irregularities in the snow, ice, and other terrain. But if you’ve got sharp rocks under that snow, the tire might be more prone to chunking with deep siping.

Wide vs. Narrow
The wide versus narrow argument in snow is just as volatile as the wide versus narrow argument in mud. If the snow is shallow enough that the tires can dig down to a hard surface without the axles becoming hung up, then a narrow tire is the right choice. If the snow is deeper than your Jeep’s ground clearance, the last thing you want to do is dig to hard ground. A properly aired-down wider tire and wheel combo will more easily float on the surface of the snow. On ice, a narrow tire and wheel combo will provide greater traction because of increased tread-to-ground surface-contact pressure. However, even though a wide tire and wheel combo will generally offer less contact pressure at the tread, if it’s properly aired down, the wide tread can mold to the uneven surface and possibly provide better traction. Think of it as the difference between whacking a small, narrow, and hard hockey puck across an ice rink versus trying to smack a floppy sheet of rubber across the same rink.

The wide versus narrow tire debate is extremely dependent on the snow depth and the tire pressure. In bottomless snow you are far better off with a wide tire and wheel combo set to a low tire pressure. The narrow tires will work well in shallow snow with a firm or icy base.

Air Pressure
Just as it makes a significant difference off-road, lowering your tire air pressure in snow will increase traction and flotation. What pressure you choose will depend on the kind of winter terrain you encounter and the speeds you plan to reach. If you are dealing with deep snow, then you want to float on top. You want to increase the tread contact patch the same way you would want to in deep sand. Many hardcore deep snow wheelers will get down into the 1 to 5 psi range. If icy roads are what you expect, you might consider dropping the tire pressure a bit for improved traction.

The non-directional military tires on this M35A2 are miserable winter tires when inflated to the max 80 psi. They acted like hockey pucks sliding across an ice rink. Airing all 10 tires down into the single digits got us out of an icy area that would have otherwise sent the truck sliding sideways into a ravine. Airing down your tires will also create a larger footprint, which helps your Jeep remain on top of deeper snow.

Radial vs. Bias-Ply
The best snow and ice tire will generally be one that has a flexible carcass. You want the tread and sidewall to be able to envelop uneven surfaces. This takes advantage of the available tread surface and helps the siping in the tread open up and grip the ice. In most cases, a lightweight radial tire with fewer plies in the tread and sidewall will flex better than any other tire type. However, if you are driving off-road, you still need sidewall and tread protection from rocks, sticks, and logs hidden under the white stuff. Bias-ply tires typically do not flex and envelop obstacles as well as a radial tire, but bias-ply tires feature a lot of extra sidewall protection, which can be incredibly helpful if the trails you venture out on in winter are littered with sharp debris. Again, it is a compromise you have to think about when considering the type of terrain you encounter in winter.

Studs, Bolts, and Chains
The use of steel traction adders, like tire studs, bolts, and chains, are usually reserved for extremely icy conditions. In many areas, the use of studded tires on the highway is prohibited or limited to specific times of the year. The studs cause damage to the road surface. On-road studs consist of two primary parts. The ultra-hard tungsten carbide pin is the component that protrudes beyond the tire tread and contacts the pavement or ice surface. The outside part of the stud is a cylindrical metal jacket that is held in the tire tread by a flange at the base. Because studdable tires are manufactured with different tread depths, studs are available in several sizes ranging from a #12 (12⁄32-inch tall) to a #17 (17⁄32-inch tall). Only new tires that have never been driven on can be studded. Tires that have already been driven on cannot be studded nor re-studded. Unseen debris (sand, salt, or stones) trapped under the stud in the molded hole could result in tire damage. Studs designed for on-road use will do very little to improve traction in bottomless loamy snow—They are just too short. A wide range of longer screw-in studs is available from companies like Grip Studs (gripstuds.com) for off-road-only applications. They are available in lengths that will make a significant performance difference on ice and packed snow off-road. However, if bottomless powder is all you encounter, the longer studs will do little to help you get further down the trail. One advantage these screw-in studs have is that they can be added to any tire at any time during the tires life. They can also be removed when no longer needed.

Dedicated ice racers often install sharpened 3⁄8-inch bolts into their tires from the inside out. This is an extreme application that has little use outside of making traction on a frozen lake or river.

Frozen lake ice racing has a specific class, sometimes called the Cheater Class, which allows bolts to be added to the tires. The tires typically receive about 100 sharpened 3⁄8-inch bolts that are up to 3 inches long. Inner tubes keep the tires inflated. These bolted tires provide almost dry-pavement-like traction on ice; however, they are a bit extreme for anywhere outside of a frozen lake or river surface.

Tire chains offer great slow to medium speed traction on ice and in some snowy conditions. The biggest advantage chains have is that they can be added to nearly any tire and then removed quickly to make the tires more streetable when needed. Unfortunately, each pair of chains is designed for a specific size tire, so they can’t be moved from vehicle to vehicle unless the tires are very close in overall diameter. In deeper snow, a chained-up tire will act like an extreme mud tire. They will cause a Jeep to dig down and possibly get stuck. For this reason chains should only be used on ice, packed snow, or shallower snow depths. There are many different kinds of snow chains. Some vehicle applications that don’t have a lot of inner fender clearance will be better off with cables similar to the SCC (scc-chain.com) Super Z or Radial Chain LT instead of the common ladder-style link chain like the SCC Quick Grip. For extremely icy conditions, consider using something similar to the SCC or Quality Chain (qualitychaincorp.com) V-Bar style link chain.

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