Tis the season, so let’s talk winter driving and snow.

When turning, the path of the front wheels is longer than that of the rear wheels, and the path of the outside wheels of a turn is longer than that of the wheels on the inside of a turn. An easy visual to picture in your head is a semi-truck making a right-hand turn at an intersection. The truck will pull very wide into the intersection, almost crossing onto the oncoming side of the road with the cab, yet the back wheels of the trailer are barely able to make it around the corner without hopping up on the curb. The front wheels traveled a further distance than the rear wheels and the outside wheels traveled a further distance than the inside wheels. Every vehicle does the exact same thing, just on a more compact scale because of a shorter wheelbase. This is where differentials come in, front and rear differentials allow the wheels being driven by the same axle to spin at different speeds. A center differential allows the front and rear axles to spin at different speeds.

An All Wheel Drive system has a front, center, and rear differential. **That is a generalization about AWD for the sake of simplicity, there are a ton of variations out there but there is always something that allows the front and rear to spin at different speeds** This allows AWD vehicles to have each wheel rotating at different speeds while still being driven and applying power. A typical 4 Wheel Drive system operates as Rear Wheel Drive until the front and rear driveshafts are mechanically locked together in 4WD via the transfer case. When you lock a vehicle in 4WD the axles can’t spin at different speeds. The result is that there WILL be binding in the drivetrain while driving anything but straight ahead. When there is binding, there is tension building, and something has to release that tension – either a front tire drags or a rear tire spins to make the front and rear axle speeds match, or the inner workings of the transfer case explode out the side of the housing and into the road. The latter being the least likely, but it does happen, especially over time with repeated binding contributing to metal fatigue. If you try pulling into a parking space with a vehicle locked in 4WD, it’ll either get stuck making a tight turn because the drivetrain is binding up, or something, hopefully just a tire, will release the force. It’s a little counterintuitive, but when you drive around in the snow in 4WD to get more traction, you’re forcing tires to break traction and slip with every curve, bend, and corner, which isn’t doing you any favors.

Our 5th generation 4Runner Limited, equipt with a Full Time 4WD system, is the best of both worlds. With a torsion center differential in the transfer case, it operates very similarly to an AWD system in that it allows all 4 wheels to be driven while letting them move at different speeds. The difference is that with Full Time 4WD the center differential in the transfer case can still be locked in 2 different gear ratios. This gives it all the same functionality as a traditional 4WD with a 2-speed transfer case. AWD has all 4 wheels driven but independent all the time. **That is a generalization about AWD for the sake of simplicity, there are a ton of variations out there** 4WD has RWD, locked 4Hi, and locked 4Lo. Full Time 4WD has AWD, locked 4Hi, and locked 4Lo.

Now let’s look at all of the advantages that come with 4WD and AWD:

1. It will help you accelerate
2. There is no 2, that’s the end of the list

4WD and AWD will not help you stop, they will not help you turn, they will not help you hold the road around a bend or switch lanes over the snow and slush channels. They will not help with anything except applying power to the ground in order to gain speed. You are effectively doubling the surface area of the contact patch that power is being applied to, but there is no change to the contact patch in any other situation. Everything else is left to the one part of the vehicle that actually contacts the ground, the tires. 4WD and AWD will help improve acceleration, but proper tires are going to help improve acceleration, safety, braking, handling, and traction in every scenario you can think up. Getting up to speed is irrelevant if you can’t control the speed once it’s there. The most advanced drive systems with all the electronics and driver aids in the world are rendered useless if the tires can’t hold the road.

So let’s look at some general classifications of tires. There are a few realistic options for tires, we’re not going to cover summer tires of R compounds.

• Mud Terrain: It’s a common misconception that mud terrain tires will be good in the snow. People think because they are big and chunky with deep tread that they will handle snow like a tank. It is true that a good condition mud terrain is a great option for off-roading in deep snow, but on snowy pavement and streets, their lack of bite is downright dangerous. Their large chunky tread spaced wide for self-clearing mud and rocks make for an impressively bad grip on winter roads. Save the mud terrains for the trail.
• All Season: The standard, most vehicles come with stock with an all season tire with the “M+S” mud and snow designation on the sidewall. These should really be called 3 season tires. The tread block design, lack of siping, and the use of rubber compounds meant for high temps that harden in the severe cold make these tires subpar for winter use. Every snowstorm that hits the front range here in Colorado ends with Subarus littered among the ditches on the sides of the road, the result of clever marketing making people think “Symmetrical AWD” paired with their stock all season tires are going to make their car defy the laws of physics and handle like a snowmobile. M+S are appropriate for colder temps and the occasional dusting of snow. Most people that live in flat regions, even if they get harsh weather, will slowly and cautiously limp their way through winter on all seasons.
• All Terrain: Not every all terrain tire is made equal, but a good baseline for use in the winter is one with the “3PMSF” 3 Peak Mountain Snow Flake” designation on the sidewall. This symbol designates the tire has been tested and met the criteria for “severe snow conditions” and extreme weather. Keep in mind that the testing criteria is extremely basic, it’s just an acceleration test on medium hard packed snow, nothing else. Braking, handling, and varying conditions aren’t factored in, but any tire with the 3PMSF designation will meet the legal requirements for winter tire restrictions.
• All Weather: Not to be confused with all season, are truly designed for all weather. This is a newer class of tires that is quickly skyrocketing in popularity. It’s a jack of all trades, 1 tire to do it all that all season was supposed to be. They can be used year round, the rubber compound won’t harden in the cold, and they tend to have lots of horizontal edge(s) across the tread pattern for an increased bite on the snow. If you live in a place with real winter, this is a great solution and should be considered your minimum required equipment. Every all weather tire will have the 3PMSF sidewall designation.
• Winter: The king of the hill that will get you to the top of the mountain, and safely back down. Winter tires, commonly referred to as snow tires, are designed from the ground up for maximum performance in extreme weather. They are typically made from a very soft rubber compound that allows them to conform and shape to imperfections across the ground surface and they have tread blocks covered in zig zags of siping. These tires have everything working in their favor to give them more bite on snow and in the cold, in order to maintain traction. If your winters are severe, winter tires should be a priority. If your winters contain mountains, they should be considered mandatory. You will accelerate faster, stop earlier, and hold the road better than everything else in foul weather. A lot of winter tires are studable for use in areas with lots of ice compared to snow, but check your local laws, studs are damaging road surfaces and therefore illegal in all but the harshest of environments. The downsides of winter tires are their inability to handle the heat and not feeling as planted at high speeds. The fastest way to kill a winter tire is to drive it when the temps get warm, so consider these seasonal use only.

With all that said, you, as the driver, are still the biggest variable in the equation. Not only is it your legal and moral responsibility to ensure your vehicle is in proper operating condition (the suspension is in good working order, the tires are in good condition and properly inflated, your brakes are fully functional, etc) but you control the vehicle. The key to safe winter driving is slow and smooth inputs, no hard acceleration, no hard braking, and no fast steering inputs. Brake early and gently. Take 10-15 seconds to switch lanes slowly. Apply very light throttle to get moving. Maintain your momentum as often as possible – if the light is red up ahead, slow down well before it to avoid making a full stop at the light. By definition, you cannot be stuck if you’re moving, try to stay rolling until the light is green and you can continue moving through the intersection. The same applies to hills, do everything you legally can to avoid stopping on an uphill incline. If your vehicle is ready, driving slow and smooth with keep you safe in the snow.