You may have heard terms like Front-Wheel Drive (FWD) or Rear-Wheel Drive (RWD) being mentioned in the context of cars. If you want to know the difference and how it might affect your next purchase decision, you will be enlightened by the end of this article.
Most cars are either pulled by the front wheels or pushed by the back wheels.
In regular day-to-day driving, you’d never be able to tell which wheels are responsible for moving the car. So does it really matter to the average driver whether the car is front or rear-wheel drive? Well, actually, yes, and for reasons other than how it affects the way the car drives.
A short history
The majority of cars being made today are front-wheel drive (FWD), but this is only a relatively recent convention. Since the earliest days of the motor car until about the late 1970s, the rear-wheel drive (RWD) layout was far more prevalent; mounting the engine up front and in a straight line with the transmission, propshaft, and rear axle was mechanically more simple, and was a solution to distribute the weight of all the heavy components.
Though the 1930s saw the advent of the mass-produced FWD car with the Citroën Traction Avant (below), it wasn’t until the 1950s that this drivetrain layout became more popular, thanks to the Citroën 2CV, Citroën DS, Saab 92 and 93, and Austin Mini.
Still, at this point, RWD remained the general convention, and it was only in the late 1970s and 1980s that car makers started adopting FWD en masse, an engineering principle that remains to this day.
The chief impetus for car manufacturers making the switch to FWD was its space-saving properties. By mounting the engine and transmission side-to-side across the car as opposed to front-to-rear in the case of RWD, more of the car’s length can be devoted to the passenger compartment instead of the drivetrain, thus freeing up more space without increasing the car’s overall length.
Nowhere is this better exemplified than in the original Mini (above), which had the ability to carry four adults and luggage within a 10-foot (3 metre) length. Likewise the latest BMW 1 Series, which has 33mm more legroom despite a 20mm shorter wheelbase (the distance between the axles) compared to its predecessor.
With the drivetrain weight pressing down on the driven wheels, FWD cars tend to have more traction and stability in slippery conditions – a trait most welcome when you come across ponding during any of our tropical thunderstorms.
That said, putting all that weight up front has its drawbacks, mainly with regards to handling. Simply put, the extra inertia means FWD cars don’t respond to direction changes as quickly or eagerly as RWD cars, which makes them less fun to drive (generally).
You’ll be hard-pressed to find many FWD cars that make more than 300hp. Much of this has to do with the way weight transfers to the rear under acceleration. If you have stood in a bus or MRT, notice how you have to brace yourself to prevent from being flung to the back?
In a car, all that weight shifts to the back and presses down on the rear wheels. This helps a RWD car because it creates additional grip on the powered wheels where it can better utilise all the available power.
When this happens in a FWD car, there’s less weight (mass) pressing down on the front wheels making less grip available. When this happens, power that can’t be utilised is wasted as wheelspin.
To mitigate this, carmakers usually locate the heavier components such as the engine block in front of the front axle. While this also helps with braking, it also makes the car less responsive to steering inputs.
You can test this out yourself the next time you visit the supermarket. Try pushing the trolley among the aisles with a big bag of rice right at the front, then move it towards the back and see which is easier.
Also, because the front wheels have to handle both steering and acceleration duties, FWD cars will wear out their front tyres much quicker than the rears, necessitating more frequent rotation and maintenance.
RWD on the other hand, may be the less common layout these days, but it certainly still has a place in this world, particularly for the cars most people deem desirable – luxury and sports cars.
This is why sports cars and luxury cars are usually RWD, because speed, dynamics and power are important characteristics of these kinds of vehicles.
Splitting steering and acceleration duties between the front and rear wheels, and having the weight of driveline components distributed more evenly means that RWD cars can serve up more precise and balanced handling, as well as handle more power.
The biggest drawback of a RWD layout is that it takes up a lot of space. Firstly, the engine and gearbox tend to be arranged in a front-to-back or ‘North-South’ orientation. To optimise handling, some manufacturers even locate the engine behind the front axle.
This in turn, means that the engine and gearbox start occupying space in the passenger compartment. If the car is big enough, like a Mercedes S-Class for example, there’s still plenty of room to spare, but in a smaller car such as the 2012-2019 BMW 1 Series, rear passenger legroom starts to get a bit squeezy.
From a manufacturing perspective, a RWD is more expensive to produce because they require more parts than a FWD car that has everything it needs in one compact package. The longer driveshaft which connects the engine to the rear wheels also adds weight which impacts fuel economy.