What’s Driving You: Comparing Front, Rear, and All-Wheel Drive Performance
Front-wheel drive (FWD), rear-wheel drive (RWD), all-wheel drive (AWD); you’ve probably heard these terms kicked around before, but what do they mean, especially in terms of road-handling performance?
The short answer is that it really depends on a few external factors like driver skill, weather, and tires, but let’s dissect how each drivetrain is typically used and perhaps help you pick your next performance instrument.
Certain automakers have staked their claim to a particular drivetrain setup. For example, Audi has been synonymous with Quattro all-wheel drive since their Group B racecars began demolishing circuits in the 1980s (which later influenced passenger vehicles). BMW, until very recently, produced rear-wheel drive machines above all. Now, front-wheel drive and xDrive all-wheel drive models have found their way into most of the brand’s lineup. Honda’s long list of affordable performance models, with the exception of its NSX, have been built exclusively on front-wheel drive platforms.
Part of the reason why automakers have traditionally gravitated towards one drivetrain or another is because development costs increase as more structures are added to a vehicle portfolio. By choosing one drivetrain to underpin several vehicles, manufacturers can apply development dollars to optimizing that setup instead of stretching itself too thin over many formats.
By the numbers
Perhaps the best way to kick of the drivetrain discussion is to understand how many vehicles sold today use which setup. By a good margin, the majority of passenger cars and trucks in America operate with front-wheel drive configurations (54% of all sales in 2013). That means the engine, transmission, differential, and driven wheels are all up front while the rear wheels come along for the ride.
The next most popular setup, and one that’s grown steadily in recent years, is all-wheel drive (34% of all sales in 2013) where a pair of differentials, one at each axle, split the power from the engine. Finally, and the segment that’s shrunk the most as more performance vehicles embrace all-wheel drive performance, is rear-wheel drive (12% of all sales in 2013), where the traditionally front-mounted engine sends power along the driveshaft to the rear wheels.
To help explain these numbers, we need to understand consumer appetites. Though gas prices have fallen for the foreseeable future, efficiency is still a strong selling point for today’s car buyers. Front-wheel drive platforms aren’t just cheaper to engineer, and therefore appear on a greater number of entry-level vehicles, they are also lighter and more fuel-efficient than other setups. By contrast, all-wheel drive systems use more components to get the engine’s power to all wheels, and therefore add weight. For the consumer, this means an extra expense at point of purchase and in terms of fill-ups. One reason AWD has become more popular is that premiums for these vehicles have decreased and performance advantages continue to grow. RWD platforms may still be the purist’s choice for performance vehicles, but in less than perfect driving conditions, and compared to a FWD car’s efficiency, they can’t match up.
Bred for the right conditions
It’s not as clean-cut as some might like, but in many ways, your environment and daily routine will dictate which drivetrain is right for you.
If you live in either a fair-weather or mild four-season climate (modest levels of snow and rain), the truth is that you can get away with pretty much any drivetrain choice as long as you shell out the money for a good set of winter tires when the weather calls for them. Still, all-wheel drive and front-wheel drive vehicles are the easiest to manage in snow and rain. The reason has to do with weight.
A FWD vehicle’s mass is pretty much all over the front tires, where power is being applied. For this reason, if the conditions are slippery, there’s usually more traction where there’s weight. In a RWD model, without enough weight over the rear wheels, the tires will lose grip easier or find it harder to ever hook up. An AWD setup goes one step further by applying power to all four wheels. Even if one or more of the tires lack traction, the others will “help out” to get a vehicle moving or assist in recovering grip.
At this point, you might be wondering what, if any, differences there are between all-wheel drive and four-wheel drive (4WD) setups. For a deeper dive on that subject, definitely check out this article, but the short story is that while both 4WD and AWD models apply power to four wheels, only 4WD models add lower gearing to maintain traction in ultra-slippery conditions. As an example, Jeep’s Wrangler uses a four-wheel drive system, which enables it to scamper up rocks, while Audi’s TT sports car uses an AWD system for the utmost grip during performance driving maneuvers. Basically, unless you intend to tame mountains, a heavy-duty 4WD system is overkill.
Depending on the price point and type of vehicle you’re shopping, many models will offer available all-wheel drive systems. The important thing to keep in mind is that you don’t need to check the AWD box. Besides the point that a good set of winter tires will get you through all but the most grueling winters, a good chunk of today’s AWD systems are only active part-time. That means that unless all-wheel traction is absolutely necessary (either at your discretion or the car’s on-board traction management system), the car will function in either front-wheel or rear-wheel drive. Granted, the point of this default is to save you fuel, but it also means that you may only use that more expensive AWD system once or twice a year.
If the vehicle(s) you’re shopping offer multiple drivetrain options, it’s a good idea to test drive each (making sure the AWD system is engaged when driving that spec). Though you may not need four-wheeled power, some drivers prefer the sense of stability and power delivery of an AWD system to a FWD or RWD setup. For those individuals, the driving experience merits a price premium.
Performance driving behavior
Now that I’ve covered the general spread of drivetrain types and applications, I’ll focus on how performance driving is impacted by each setup.
Front-Wheel Drive Behavior
First, I feel it is my duty to defend the lot of front-wheel drive performance cars. Unjustly these vehicles have earned a bad reputation in the enthusiast community. The complaints are pretty simple: since the front axle on a FWD car is in charge of steering and managing all the engine’s power (as opposed to just steering or only managing a portion of the power like other setups), two things can happen. The first is called “torque-steer,” a phenomenon where the torque delivery overwhelms the front tires and “steers” them somewhat wildly, forcing the driver to cut down acceleration or fight the steering wheel. The second issue is called “understeer,” where maximum steering input paired with throttle pushes the vehicle to the outside of a corner.
I won’t attempt to deny that each of these issues is inherent to FWD configurations, but I will place some responsibility and blame on the driver in these circumstances.
As FWD performance models – like the Volkswagen GTI and Ford Fiesta ST – become more powerful, torque steer can be more of an issue, but automakers have made incredible progress lately to nullify the condition. By using intermediate shafts to reduce the flex of a longer v. shorter driveshaft, most modern vehicles only experience a “pull” on the steering wheel under full, from-a-stop, acceleration. Other techniques include electronic differentials and power damping controls. To avoid going too far down the rabbit hole, I’ll simply say that contemporary vehicles come equipped from the factory to manage the maleficent torque-steer problem, so complaints about that issue carry far less virtue than they once did.
As for understeer, that’s completely under the driver’s control. I, too, once wrote-off FWD vehicles as understeering contraptions, but after years of track driving and training from racing pros, I have a new appreciation for how much manipulation a driver can apply to a FWD car. As your skill increases, you can rotate a vehicle and never have to take your foot off the throttle when cornering. Carry too much speed into a corner or just rely on more steering angle to solve your problems and you’ll end up in the barrier, but that’s true of any drivetrain setup. Proper braking, turn in, steering input, and throttle modulation can turn any FWD vehicle into just as potent of a track weapon as a RWD or AWD vehicle.
Rear-Wheel Drive Behavior
Speaking of, why do purists swear by RWD designs? For several reasons, a rear-wheel drive system can afford an extra degree of control to a skilled driver, but it is also a more difficult drivetrain to master. In terms of acceleration, a RWD system will also be quicker than a FWD setup because as weight transfers to the rear off-the-line, the front wheels lose grip and the rear wheels gain more.
On a track, rear-wheel drive vehicles can be manipulated to slide or pivot that much easier than a FWD or AWD model around a corner. This is because power can be used to break traction on the rear wheels, while FWD or AWD models must rely on momentum to rotate. Finally, RWD configurations are usually designed with near-perfect weight distribution (50:50) thanks to a front-mounted engine and rear-mounted transmission and differential. In performance driving conditions, that balance translates to neutral handling, where subtle inputs to throttle, steering, or braking have greater impact.
All-Wheel Drive Behavior
So, you might imagine, all-wheel drive must be the best of both worlds. Well, yes and no. In terms of acceleration, it’s true: all-wheel drive usually is the quickest off the line with little to no slip under full power. On the track, AWD systems enable incredible levels of grip during cornering, but all that grip can sometimes get in the way of driver-controlled maneuvers.
If a new driver picked one setup to compete with seasoned pros, all-wheel drive would be the best choice. Advancing to fast lap times on an AWD vehicle is more manageable than the same feat in both FWD and RWD configurations because it’s easier to recover from mistakes and easier to push a vehicle in each corner without dire results. However, when it comes to next-level driver mechanics, AWD vehicles are actually more difficult to manipulate than their FWD and RWD counterparts. An unbiased (front or rear) all-wheel drive system strongly resists artificial movements like rotation from trail braking and oversteer. Grip is great, but experienced drivers can get more out of a vehicle that let’s them “force” their will in certain conditions.
With the market demanding more crossovers and all-purpose vehicles than ever, the trend of front-wheel and all-wheel drive vehicle development will continue. It has become simpler than ever for automakers to reconfigure FWD models into AWD forms (with a front-wheel power bias), so I’d expect the vast majority of vehicles to be available in both configurations very soon.
I also didn’t touch on how hybrid and electric systems impact drivetrain performance, but as electric assistance works its way into every segment of the industry, power application will be more on an individual wheel basis. Compact batteries and electric motors will likely mean each wheel will use its own power source while overall vehicle performance is controlled via a central computer. We’ve seen this on concepts and supercars like Acura’s new NSX to excellent performance results. Consumers who enjoy all-wheel drive traction will undoubtedly appreciate when this setup works its way to mass-market models.
The sad truth is that RWD-exclusive systems are already going the way of manual transmission and in the not-too-distant future, the only way to find a more demanding RWD handling experience will be to collect past and present classics. If you’ve never had a bout with such a car, get behind the wheel soon…just respect how quickly you can end up facing backwards.