What Makes a Car Good in the Snow?
Four-wheel drive, all-wheel drive, tires, ground clearance, and weight distribution. Let’s settle this debate once and for all.
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If you want to safely drive in winter weather, then fitting a set of studless winter tires to whatever vehicle you already own is the most effective thing you can do. But, beyond those studless winter tires, are there things a vehicle can be equipped with that may also help to a lesser degree? The answer is a little more complicated than you might think. Let me break it down.
Snow Tires, a Recap
Tires are the only component of your vehicle in contact with the surface you’re driving on. That makes them the most important component on your vehicle. Various drive systems like four- or all-wheel drive are only able to take advantage of the traction provided by your tires. Same with your brakes.
The vast majority of cars and trucks are fitted with all-season road tires when they leave dealer lots. That name is misleading. The rubber compounds used to make all-season tires work best in temperatures above 45 degrees. When it gets too cold, they begin to harden like a candy bar in the fridge, making it unsafe to rely on them even on dry pavement in below-freezing temperatures. Winter tires are made from rubber compounds that, not only remain pliable at low temperatures, but which also include microscopic pores. Those wick the thin layer of water that the weight of your vehicle melts as it drives over ice, allowing that flexible rubber to mechanically key with, and therefore provide grip on ice.
This rubber compound that remains flexible and able to stay in contact with the surface you’re driving on at low temperatures is what enables modern studless winter tires to provide reliable, consistent levels of grip across the ever-changing variety of conditions you’ll find on North American roads in the winter. Because we plow roads on this continent, drivers here cannot expect to drive on a consistently snowy surface, even in the winter in northern latitudes. Studded tires are designed only to work in conditions where tires never come into contact with pavement. Driving with them on pavement rapidly wears out the studs, eliminating any grip they might provide. And, studded tires do not have traction benefits in winter conditions over the studless alternative.
Run tires that are suitable for the winter conditions we drive in: studless winter tires. Put them on in November, and take them off in April.
Which wheels do you want to drive? The answer may seem simple, but the systems that provide it are commonly misunderstood.
Front-Wheel Drive: The vast majority of new cars locate their engine at the front. So, front-wheel drive will typically offer a little more grip, all other things being equal, over a rear-wheel drive car. Pulling, rather than pushing also makes the driving experience a little more predictable in slippery conditions, and FWD is a better choice than RWD for low-information drivers as a result. But, once the wheels on a FWD car lose traction, there is nothing a driver can do but slow down. Hit the gas in slippery conditions in a FWD car and you will experience understeer. The car will fail to continue its way around a corner.
Rear-Wheel Drive: It is easier to package a FWD car, and they are often cheaper as a result. But a RWD car with balanced front-to-rear weight distribution will typically offer superior dynamics for experienced drivers, with the tradeoff that they can prove difficult to control for the inexperienced or inattentive. A RWD car with even weight distribution, or one with a mid or rear-mounted engine that puts more pounds over the rear wheels will have as much, if not more, traction than a FWD car. The various differential traction aids typically present on high-performance RWD cars help even more. Altogether, RWD is capable of offering more control to experienced drivers, but that control comes with equal amounts of challenge. Hit the gas in slippery conditions in a RWD car and you will experience oversteer; the rear of the car will attempt to overtake the front.
All-Wheel Drive: Power follows the path of least resistance within a drivetrain. So, in an AWD vehicle with an open center differential, that power goes to the wheel with the least traction. Hit the gas in slippery conditions, and one of the wheels will spin freely, while the others receive no power. This is good for safety. Because the wheel with the least grip gets all the power, the wheels with the most grip are able to prevent the car from initiating a slide or spin. But it is not good for capability. It does nothing to help you climb a slippery hill. So, manufacturers of AWD vehicles endow them with a variety of mechanical or electronic devices designed to help match wheel speeds between the front and rear axles, or across those axles to the tires at the front or rear of the vehicle. AWD works all the time, without any driver involvement. That, plus the added weight of the system is why AWD vehicles return lower fuel economy figures than their 2WD equivalents. It also means that the driver does not have to think about its function; it just works. AWD is a better choice for low information, inattentive drivers as a result—it’s idiot proof.
Four-Wheel Drive: 4WD locks the speeds of the front and rear axles together, so the wheel with the least traction can only spin as fast as its counterpart on the opposite axle. This effectively doubles your traction over two-wheel drive. Hit the gas in slippery conditions in a 4WD vehicle, and it will acclerate. But, because the front and rear axles need to spin at different speeds as they go around a corner when there’s good grip, 4WD can only be employed in slippery conditions. During the winter, a driver must pay attention, and switch 4WD on and off as they cross between areas of consistent snow or ice, and patches of bare pavement. Leave 4WD engaged on dry pavement, and you will slowly damage your drivetrain, while running the risk of losing control. Forget to engage 4WD in slippery stuff, and you gain none of its benefits. 4WD components are typically heavy, and engaging it adds resistance to your engine. That’s one reason why 4WD vehicles return typically poor fuel economy.
4WD vehicles can also be equipped with a low-range gearing, which you may find expressed as something like “4LO” on a dial, switch, or lever inside your truck. Where neither 4WD nor AWD are capable of improving your braking ability in winter conditions, the extreme multiplication of engine forces achieved by low-range gearing will allow you to descend steep, slippery slopes with greatly enhanced control. Drivers who regularly need to get down steep, icy driveways, for instance, need low range gearing to do so safely.
Locking Axle Diffs and Electronic Traction Aids: You may have noticed by now that, when the going gets slippery, 4WD actually just drives two of your wheels. There’s also a differential between the wheels on an axle. Again, those need to spin at different speeds to round corners when you have good amounts of grip. But locking their speeds can increase traction. Only a vehicle with locking diffs at the center, front, and rear can truly drive all four wheels at equal speeds. Well, that used to be the case. Now, sophisticated traction control systems employ the antilock brake system to match wheelspeeds by tweaking individual brake calipers. Where traditional axle lockers can be challenging to engage and disengage, the computer-based alternative self-actuates, only providing additional traction in the split second it’s needed. Because locked diffs impair a vehicle’s ability to turn, electronic systems additionally have the advantage of working without compromising your ability to steer. I prefer using the electronic systems as a result—when they work. There is much variability in the capability of these systems between manufacturers and models. Ford and Land Rover do the best job, with the least intrusive and most capable systems. Toyota’s efforts are capable, but cause a lot of lurching and noise. My experience with electronic traction aids on AWD cars has shown them to quickly overheat and stop working when attempting even moderate challenges. High-performance 2WD cars may also feature mechanical traction aids in their differentials, or now even electronic versions of such.
Which One Is Best? Because AWD is idiot-proof, AWD seems like the better option for most people. It will help provide a little extra safety, and maybe even a tiny bit of additional capability. If pushing a button to engage and disengage 4WD as needed doesn’t seem like an intimidating feat of mental gymnastics, then it will better enable your car to take advantage of your studless winter tires than AWD can, allowing you to make progress in more challenging conditions. But, even talented drivers can be caught out by the ever-changing conditions winter brings. Hit a patch of black ice on what you thought was dry pavement, and you’ll wish you had AWD.
So which is best? How about both. Vehicles with full-time 4WD nominally operate in AWD, while still giving you the ability to lock the center diff, and enter true 4WD. Or even access those low range gears. Land Rover pioneered this system, which combines on-road safety with off-road capability, but it’s since been adopted by many other automakers. A full-time 4WD system with modern electronic traction aids, and low range gearing (fitted with studless winter tires), can be considered a best possible arrangement for winter driving.
Electronic Safety Aids
All of these are mandatory on all modern vehicles. But it’s still a good idea to understand how they work.
Antilock Brakes: Highly trained drivers learn how to threshold brake at high performance driving schools. That involves applying just the right pressure to the brake pedal, and varying that pressure based on the feel that pedal delivers, to decelerate a vehicle just on the edge of locking its tires. Because that skill is challenging to learn and requires drivers to remain maximally aware as they drive, it’s not really a skill that’s practical for on-road driving. ABS computers aren’t sophisticated enough to achieve it either, so they actually pulse brake force between locking and unlocking the wheels in incredibly quick increments. This is a good compromise, providing good braking performance while retaining the ability for the driver to steer. Getting the most out of your ABS System in an emergency is simple: just apply the brakes as hard as you can, no matter the conditions, then try and steer around anything you’re about to hit. Keep standing on that brake pedal until you’re clear of the obstacle, or have come to a complete stop.
Traction Control: In effect, TC works similarly to AWD; it cuts power to prevent a slide or spin caused by a driver applying to much throttle. It’s a safety feature that only works under acceleration, and can only ever slow you down.
Stability Control: This works through the ABS system to constantly monitor individual wheel speeds to determine if your vehicle is about to slide or spin, then applies the calipers individually, and in fraction of a second, intervals to correct or control those slides and spins. Most of the ability of a modern car to avoid a crash in slippery conditions that is inaccurately credited to AWD is actually thanks to stability control. It’s the most important safety technology since the airbag.
Weight Distribution, Ground Clearance, and Wheelbase
We’re getting to the hairsplitting portion of this article. Worry about tires, safety systems, and driven wheels long before you start to stress about adding weight to the bed of your pickup.
Let’s start with those pickups. They have a couple of things going for them and a couple of things working against them when it comes to snow driving. The first is weight. All other things being equal, a heavier vehicle will have more traction than a lighter vehicle. They also tend to have longer wheelbases (the distance between the center of the front and rear wheels) than passenger cars. That length slows the initiation of a slide or spin, giving you more time to correct it in a more gentle manner. Lastly, pickups usually have a little bit of ground clearance, which helps their bodies clear very deep snow, a fairly rare condition to encounter on a road.
Pickups also tend to have two major downsides: weight distribution and the fitment of part-time 4WD. An unladen pickup usually carries most of its weight over the front wheels, where the engine, passengers, and cab are. Because most pickups nominally operate in RWD, this means those wheels have less traction. Drivers try to compensate for that imbalance by carrying weight in the bed of their trucks. This can be problematic on its own. Unless that load is secured, it may shift during driving, under heavy braking, or in a crash, suddenly altering the dynamics of the vehicle. If that weight is carried too high, it may contribute to a rollover. If you feel that you must add weight to the bed of your pickup, then only add enough so that you feel you’ve addressed its lack of traction, make sure that load is secured, and try and carry it as low as possible.
Shorter wheelbases and the more balanced weight distribution those bring are one reason why SUVs perform better off-road and in snow. There are also more options for full-time 4WD in that segment.
One area where drivers don’t tend to think about weight distribution is in tire size selection. Unless you are off-roading through deep powder, where you need good flotation, a narrower tire will provide superior grip to a wider one. Scott Brady, the publisher of Overland Journal put together an excellent white paper on that topic. Tire size selection can be tricky for the uninitiated. I use this free tire size comparison tool to help.
What About Chains?
Even though you’re required to carry chains on some blizzard-prone highways out west, tire chains aren’t really relevant to modern driving here in North America. Studless winter tires are better able to handle slippery conditions on the road, and once you encounter the kind of very deep snow those tires might not be enough to handle, chains really aren’t going to get you much further. Today, I see chains primarily as a tool for experienced off-road drivers who want to go out and play with their trucks in deep powder. And, even then, you have to be very careful to pick a tire size, wheel, and suspension setup that retains enough clearance so that the chains won’t shred your vehicle’s mechanical components. Carry a set of cables (an easier, cheaper version of chains) if you’re traveling through an area that requires them, but don’t think of them as a replacement for studless winter tires; just a legal requirement you’re satisfying.
Just Tell Us What to Buy Already
Most drivers only need studless winter tires; the car itself is less important. But, if you are serious about maximizing your snow capability, then you’re going to need either a healthy budget for a new car or the willingness to put up with a used one.
The cheapest new vehicle I can think of that achieves our full formula here (full-time 4WD, modern traction aids, low range gearing, a little bit of clearance, and decent weight distribution), is going to be a Toyota 4Runner Limited, which starts at $48,000. The crazy thing is, it’s that model which represents the best value in the 4Runner lineup, offering more of the things you can’t buy in the aftermarket than the more expensive TRD Pro, which attempts to justify its premium only with features you’d be better off upgrading yourself.
In the used market, that same vehicle, but a few years old, is a good option. As is the previous 4th generation 4Runner (2003-2009). V8 4×4 versions of that model all includ full-time 4WD and low-range gearing.
For larger families and people who don’t have significant off-road needs, the Kia Telluride represents a unique option. Think of it as a Subaru Ascent, with the inclusion of an electronic center diff-lock if you spend up to the $35,000 AWD model. That means at speeds below 25 MPH, you can actually run the thing in genuine 4WD mode while using AWD at all speeds.
If you want a pickup, then the Ford F-150 Raptor ($53,205) is your best option for winter use, as it also comes equipped with full-time 4WD, and with the best suite of electronic traction aids available anywhere, in addition to a rear differential lock. Just don’t be under the impression that the stock BF Goodrich K02s are up to handling most winter driving. Those are fine in snow, but do not provide adequate grip on ice.
The Lexus GX460 also starts at $53,000, and includes full-time 4WD, low range gears, and electronic traction aids. That’s a similar vehicle to the larger $84,000 Toyota Land Cruiser, which is my family’s choice. We’re running Bridgestone Blizzak DM V2s on it. Those are Tire Rack’s top-rated winter tire for the crossovers and SUVs mentioned here, and hands down the most capable winter tire I’ve ever experienced.
Last weekend, I found myself needing to accomplish a last-minute errand that involved a seven hour drive to Salt Lake City and back. Driving down from Bozeman, Montana, in that Land Cruiser on Blizzaks, I experienced everything from dry mountain roads to a total whiteout blizzard to fresh snow to an ice storm in which multiple vehicles spun off the highway around me. All the while, I just drove along like usual, going a little slower when necessary, and feeling confident the entire way. Driving in winter doesn’t have to be dangerous, you just need to understand some basic stuff about how vehicles work, then take advantage of that knowledge.