February 25, 2013 8:00 PM | By Mark Atkinson for MSN Autos

FWD vs. AWD: What's the difference on the road?



2013 Subaru Legacy tackles Mecaglisse's ice tracks (© Photo: Subaru)

2013 Subaru Legacy tackles Mecaglisse's ice tracks

AWD can get you going, but are there differences beyond the traction advantage?
Saint-Donat, Que. — Subaru, rather smartly, recently put on an event to show off the benefits of its all-wheel drive systems against current market favourites that "happen" to be front-wheel drive. We say happen to be because Subaru claims that now most of the trade-offs traditionally associated with all-wheel drive — namely a higher price tag, increased weight, poorer fuel economy — have been eliminated.

In broad terms, the 2013 Legacy is only five to 10-horsepower shy of the Toyota Camry and Honda Accord, won’t get quite as far on a full tank, but actually starts a few hundred dollars less than either. And all that includes one of the more sophisticated all-wheel drive systems in the industry.

Held at the Mecaglisse ice-racing/winter driving facility north of Montreal, Subaru gathered a couple Camrys and Accords in their most popular trims for comparison against their similarly equipped Legacys. Every vehicle was equipped with the same Bridgestone winter tires in the correct size recommended by the car manufacturer, so this whole exercise was as scientific as possible.

As you might expect, there really wasn’t any comparison to be made; the Subarus were plainly in their element. However, there were plenty of opportunities to polish our winter-driving skills on skidpads, road-courses and even a teeny tri-oval. But even though the event was designed to demonstrate the advantages of all-wheel drive, there was still a lot to learn about the behaviours of front-drivers and how to make do in terrible conditions.

General Tips

At the wheel of a Subaru Legacy 3.6R (© Photo: Mark Atkinson)

Protip: Keep your distance. Camrys are interesting, but not so interesting you'd want to make contact with one.

Regardless of what vehicle you’re driving, in slippery conditions, every input should be very smooth. Ease on the brakes, feather the throttle, steer with a light touch. Violent or jerky manoeuvres will only break what little traction you already have. So, knowing that, having enough weight transfer to maximize traction without breaking it is a delicate balance.

Understanding how weight transfer affects your vehicle’s handling in emergencies is even more important in winter since every extra ounce of extra grip can mean the difference between turning and sliding. For example, say you’re traveling in a straight line at a steady speed and something jumps out onto the road in front of you. If you simply jam on the brakes, the helpful weight transfer won’t load up the front tires fast enough and the tires will most likely slip and slide. However, if you ease onto the brake to get the weight moving forward and then finish braking rapidly and smoothly, your tires will have a better chance of doing their job.

The same goes for turning, so regardless of how many wheels you have that are driven, getting the weight transferred to the outside tires without breaking traction is your goal.

Finally, keep your eyes up and always look where you want to go, not where you’re going. In an emergency situation, find your escape route and keep your eyes locked on that point, and your chances of success increase exponentially. Otherwise, if you target fixate — stare at the thing you’re trying to avoid — your mind and body will subconsciously steer you right into it.

Understanding AWD

A 2013 Subaru Legacy 3.6R (© Photo: Subaru)

Not all all-wheel-drive systems are created equal. Knowing what kind of system your car features will help you understand how it will drive.

It is a little amazing to imagine that only Subaru, Ford (with its higher-end Fusions) and Suzuki (Kizashi) offer AWD midsize sedans. It's a bit odd given the prevalence of AWD in the luxury segment, and the fact that a few years ago, Chrysler, VW, and other brands also offered AWD midsize sedans.

First, not every all-wheel drive system is identical. Some are full-time (permanent), others only send power to slipping wheels when needed, meaning it’ll be two-wheel drive most of the time and as such, drives like a two-wheel-drive car. Also, the ratio of how much power gets sent to each axle — or wheel, if the system is very advanced — varies from model to model. Subarus with manual transmissions generally split power 50/50 front-rear, but automatic versions are closer to 60/40.

High-performance models will generally offer more rear-biased settings because it makes the car behave more like a rear-drive sports car. BMW, Mercedes-Benz, Porsche — and all the hot Audis and Nissan GT-R — generally start at 40/60 front/rear but can go as much as 90 or 100 per cent to the back axle in situations that demand it. However, those situations are generally never found on snow or ice, which is where this discussion focuses.

Understanding Skids
There are essentially two types of skids you’ll encounter when driving: understeer and oversteer. Understeer (pushing or “tight” in NASCAR talk) happens when the front tires break traction, while oversteer (tail-happy or “loose”) is when the rears are the culprits.

Understeer

2013 Honda Accord (© Photo: Mark Atkinson)

A 2013 Honda Accord understeers its way around a corner

There are a few things you can do when encountering understeer: let off the gas gently and if that doesn’t work, unwind the steering wheel a little. It seems counterintuitive to steer ‘right’ when all you want to do is go ‘more left’, but it gives the tires a better chance of gripping again since you’re asking less of them.

Generally, in a front-wheel-drive car, if both of those fail, you’re just along for the ride ... if you’re confident, you can always try and give the handbrake a little tug, which will break traction at the rear, causing oversteer and more rotation. But fewer cars these days — including the Toyota Camrys we had on hand — have a hand-operated emergency brake, preferring either a pedal or electronically-activated one.

Rally drivers would also suggest left-foot-braking as a method of getting the back-end around in a FWD, but that’s a skill best learned in abandoned snowy parking lots (or a facility like Mecaglisse) where there’s less pressure and more chances to experiment.

All-wheel drive offers a driver more options when dealing with understeer, including having the system route power to the back axle where the tires still have some grip. That helps to rotate the vehicle ever so slightly. Some can be coaxed from understeer into oversteer with plenty of throttle and the powerful underhood computers.

Oversteer
Because of modern suspension tuning that favours “safe” understeer, and anti-skid technologies like stability control, you’re generally less likely to encounter oversteer than understeer. However, having the tail step out when you’re not expecting it is generally a moment you’ll remember.

Dealing with oversteer in FWD or AWD means turning the steering wheel ‘into’ the skid, meaning the same direction the tail-end wants to go, and increase the throttle a tad. That gives the front wheels a chance to ‘pull’ you out of the slide. Hitting the brakes or even letting off the gas too fast can make the situation considerably worse: the already sliding rear will have even more weight transfer and force behind it, meaning a likely spin-out.

Other observations

A Subaru Legacy makes its way around Mecaglisse

How a midsize sedan reacts on pavement can be very different than how it reacts on snow.

Just because your car is FWD doesn’t mean it’ll handle or react like any other FWD. For example, the 2013 Honda Accord and Toyota Camry are completely different animals. In fact, the two took on completely different personalities than you’d find in the dry. In the Accord — usually a more enthusiastic performer with sharper reactions — all it wanted to do at Mecaglisse was plow straight ahead. Only by using the handbrake could anyone get the back end to help out at all, it was very unfriendly and several times came very close to understeering nose-first into the snowbanks.

By contrast, the Camry, that bastion of boring predictability and cushy responses, was the biggest surprise: in certain conditions, its natural inclination was to oversteer, something both instructors and drivers found useful, but probably more disconcerting for buyers who wouldn’t expect that more enthusiastic setup from Toyota.

Even the different Legacy models Subaru brought out were significantly different to drive. The volume models that best matched the Accord and Camry used four-cylinder engines and CVTs, and felt pretty stable and solid. There was a 3.6-litre six-cylinder model there for demonstration purposes too, but it uses a traditional five-speed automatic transmission and more neutral AWD settings. Easily the most fun and confidence-inspiring to drive.

Conclusion
The best advice we can give is to practice, practice, practice. We’re all extremely busy with kids, mortgage payments, jobs and all the responsibilities that go along with them, but find time to go play and experiment in an empty parking lot. Practice braking, inducing oversteer, how to play on that edge of grip and traction. This isn’t being a hooligan on someone else’s property; you’re building life-saving skills and techniques that we all need to survive.