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FWD, RWD, AWD and 4WD: What’s The Difference And Why Should I Care?

Posted in 4x4, Car Buying, Car Tech, Cars, driving, General, Guide by Kurt Ernst | June 28th, 2010 | 11 Responses |

Okay, then...

Enthusiasts aside, most people buy cars because of a certain need. Maybe you’ve got a long commute and you want to save as much money on gas as possible, therefore your options come down to a hybrid or a diesel. Maybe you’ve got four sprogs to haul around and you need to keep them pacified on road trips; you’re going to be shopping for a minivan. Maybe you live in hurricane country and are preparing for the zombie apocalypse, like yours truly; in this case, you want an SUV with legitimate off road capabilities.

Most new car buyers never stop to think about what wheels drive their car or why it matters. Back in the 1970s, virtually every car sold in the U.S. was rear wheel drive, so buyers didn’t ahve a choice to make. There was a wholesale change in the automotive industry in the early 1980s, when automakers decided that they could save money and increase profit by switching to a front wheel drive layout. Better yet, they found ways to market front wheel drive as a benefit for their customers. But is it really?

Shakespeare once wrote that, “Tis nothing inherently good nor evil, but thinking makes it so”, and that kind of sums up the whole push your car or pull your car debate. Below we’re going to look at four different types of drivetrains, and go into a few pros and cons of each. If you already know this, read it anyway because yo may learn something. If you don’t know it, I’m hoping it makes your next car buying experience slightly less traumatic.

Front Wheel Drive (FWD)

FWD became the standard of the automotive industry when manufacturers realized they could save cost (by reducing the number of components in the drivetrain) and increase interior room (by eliminating the transmission and driveshaft tunnel) by adopting this layout. Customers were told that putting all the weight over the front wheels would increase traction, and that rear wheel drive cars, with their tendency to oversteer on slippery surfaces, weren’t as safe as front wheel drive cars. It didn’t matter that handling suffered in early FWD cars, since most FWD cars didn’t have sporting intentions.

So is front wheel drive a better platform than rear wheel drive? The answer is, “It depends on your expectations”. Front wheel drive cars carry the weight of their engines and transmissions up front, which makes the car nose heavy. While (in theory, at least) this does put more weight over the drive wheels, it also makes the car more prone to understeer at the limit. Rather than sharing the responsibility for acceleration, braking and steering across four wheels, you’ve got only two to handle all of that. Worse, when braking, almost all of your FWD car’s weight is transferred to the front wheels.

On high horsepower front wheel drive cars, torque steer, where the car pulls sharply to one side of the road, is pronounced. This effect makes it difficult to smoothly accelerate and steer the car in a straight line, especially if you’re turning from a stop. Many FWD cars with sporting intentions take steps to limit torque steer, but you can’t eliminate it.

Front weight bias can also make FWD cars less stable under heavy braking, as weight transfer to the front of the car unweights the rear wheels. In the hands of an inexperienced driver, heavy braking and simultaneous steering can produce sudden oversteer, and most drivers who do track days in FWD cars have fun stories to tell about this. I know I do.

So what’s the bottom line? FWD is fine for daily drivers, but less than ideal for track work. You can have FWD cars that handle quite well (second generation Lotus Elan, Mini Cooper, Mazdaspeed 3, VW GTI, Honda Civic Si, etc.) and are capable of turning fast lap times, but this platform lacks the balance of RWD. If you ask me, a sports car can be RWD or AWD, but no true sports car is FWD.

Rear Wheel Drive (RWD)

RWD was the industry standard for years, and is still the standard for paved track motorsports. You won’t see a Sprint Cup car, IndyCar, F1 car or endurance racer in FWD anytime soon, since RWD still offers the best balance and handling.

Why so? First, let’s think about weight distribution in cars. The more evenly you weight a car, the more neural its handling will be. Sports car manufacturers generally seek a 50/50 weight distribution front to rear to achieve this balance, which is why cars like the BMW 3 Series and Mazda Miata handle so well. Even under heavy braking, more weight remains over the rear wheels than in a front wheel drive car; likewise, under heavy acceleration, weight transfer to the rear of the car actually puts more weight on the drive wheels. You can’t argue with physics.

Now, let’s think about turning. RWD cars don’t power the wheels responsible for turning the car (unless you’re drifting, which is a whole other topic), so there is generally more communication from the front wheels. No matter how much power a rear wheel drive car makes, there’s no such thing as torque steer.

But front wheel drive cars are better in the snow, right? Again, the answer is “it depends”. One of the best snow cars I ever had was my old BMW 3 series, with snow tires. I could climb hills that left FWD cars spinning their wheels, but I attribute this more to the advantage of snow tires over all season radials than any advantage of platform. If you live in snow country and drive a car with RWD, snow tires should be a mandatory purchase. If you live in snow country with a FWD car, all season radials will probably get you through most weather (but snow tires are still a really, really good idea).

When it comes to sports cars, the classics remain RWD and I’ll always have one in my garage.

All Wheel Drive (AWD)

AWD generally indicates a car that has all four wheels driven at all times. AWD systems split torque from front to rear, with “commuter” AWD cars giving most of the power to the front wheels and “sporting” AWD cars favoring power to the rear wheels. As Audi proved in racing circles with the debut of Quattro AWD, sending power to all four wheels allows drivers to get on the gas earlier and can even correct a lot of novice driver mistakes.

On a race track, AWD cars are much more confidence inspiring than either FWD or RWD platforms. FWD and RWD cars teach you hard lessons at the limit, but AWD cars will rarely rap your knuckles with a wooden ruler unless you do something really stupid.
Once you learn an AWD car’s balance, it’s pure driving bliss to lightly drift all four tires in a corner.

The downsides to AWD are increased purchase cost, higher maintenance and repair costs and lower fuel mileage. The benefits of increased traction are well known to drivers of Mitsubishi Evos, Eclipse GSXs, Subaru STIs, Audi Quattros and Porsche Carrera 4s. Most manufacturers even offer grocery getters in AWD, so even drivers who’ll never turn a wheel on the track can benefit from this kind of platform.

Four Wheel Drive (4WD)

Four wheel drive generally indicates a rear wheel drive drivetrain that can be shifted into four wheel drive when conditions demand. This is the system most often found on pickup trucks or SUVs with genuine off-road capabilities, and it has the benefits of both a rear drive and all wheel drive layout. Vehicles with 4wd systems car usually switch from RWD to AWD while moving, enabling the driver to increase traction as needed. Most 4wd systems have several gear ranges as well, allowing trucks to haul heavy loads over steep and rough terrain.

The downside to 4WD systems is that they require input from the driver to engage power to all four wheels. Most 4WD drivetrains aren’t meant to be used on dry pavement, as the front differential can’t accommodate inside and outside wheels turning at different speeds when the vehicle is in 4wd mode (the front differential remains open in RWD mode, allowing the vehicle to be driven on dry pavement with no issues). As with AWD, there are more components to maintain and replace, but you don’t get the fuel mileage penalty of an AWD system.

If you absolutely, positively need to get from point A to point B in any kind of weather, 4WD is the best way to stack the deck in your favor. If you’ll never take your truck off road, and simply want better footing for winter (or wet weather) driving, then AWD should work just fine for you.

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11 Responses

  1. Joe Cefola says:

    GREAT article!!

  2. Set says:

    “Most 4WD drivetrains aren’t meant to be used on dry pavement, as the front differential can’t accommodate inside and outside wheels turning at different speeds”

    That’s because there is no center differential, like in an AWD platform. The front diff is (normally) still open, and able to do just as good a job with the inside/outside wheels spinning differently, however, the transfer case is locked, which requires one wheel on the front and one wheel on the back to spin at the same speed. (This is assuming both front and rear axles are open.)

    Otherwise, a really good article.

  3. Kurt says:

    Set, good detail and thanks for filling in the blanks!

  4. Dave says:

    I’d actually never really knew the difference between AWD and 4WD. I had an idea, and I was on the right track at least, but never really knew for sure. Thanks for the info Kurt.

  5. Taylor says:

    You do inccur a fuel mileage penalty with 4WD. Even though it is not being constantly driven, there is the weight of the system to consider.

  6. Jake says:

    I’ve been wondering what the difference between four wheel drive and all wheel drive was for quite some time. Thanks for finally explaining it!

  7. Kurt says:

    Jake, thanks for reading.

  8. Connie says:

    Great article. I didn’t know what is the difference before. Now I understand more. I wonder if 4 wheel drive cost more fuel than FWD.

    • Kurt Ernst says:

      Thanks Connie!

      Generally speaking, both AWD and 4wd will use more fuel than an equivalent FWD or RWD vehicle.

  9. michel says:

    AWD is the best choice for the performance-minded consumer who values high-speed grip and great dry-weather handling, especially during turns.

  10. Jason says:

    Hi, my bum hurts when i drive 4wd, makes me tingle in my minge