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Driving Out Confusion

Driving Out Confusion

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Automotive Journalist and featured Swansway Group author John Swift discusses the difference between FWD, RWD and AWD. Contact us if you have any questions.

It can be very confusing; what does the trade actually mean when it refers to front wheel drive, or RWD, AWD and 4x4

Here we explain what the terms mean, why there are differences and the pros and cons of each

 Every car has an engine which produces power, but without a way to transmit that to the road it won’t move an inch; for that it needs what is called a drivetrain which essentially is the gearbox, a shaft from that which turns to drive something called a differential, which splits the power and takes it through driveshafts to the wheels which then go round.

Still with us? Don’t worry, it gets easier.

Front wheel drive (FWD)

In the olden days engines used to be placed longitudinally in the engine bay – north/south as it was referred to – with the gearbox on the end and the power had to be taken to the back wheels as there simply wasn’t the room in the engine bay to have it any other way.

That’s OK, but there were the two penalties; the extra weight of having a shaft running under the car from the front to the differential at the back and the amount of space it took up, reducing the room available for rear seat passengers.

Others – most notably Citroën with its Traction Avant system – tried front wheel drive but the real breakthrough for the volume car market came with the original Mini.

black and white image of a smiling man leaning on a car with the bonnet up

Its designer, Sir Alec Issigonis, cleverly designed it so the engine was up front but placed sideways –east/west – and the gearbox sort of underneath it. The driveshafts came out of the side instead of the back so they could drive the front wheels and hey presto, you instantly had the quart in a pint pot car. This was a car that was small overall but gave an unprecedented percentage of its space to the passengers.

Austin Seven / Morris Mini-Minor Longitudinal section, 1959

Where Mini led others have followed and today virtually every volume car has front wheel drive. It is lighter, but most of all, it is much more space efficient.

 Rear wheel drive (RWD)

There are still cars which have rear wheel drive and inevitably they are high performance coupes. Usually, but not exclusively, their engines are behind the passenger cell, just after your shoulders, and there are two main reasons why they are RWD.

The engines are put there to give better weight distribution, so most of the car’s weight is between the front and back wheels rather than favouring one end. This hugely improves the handling and responsiveness but, as you will have read already, it does mean that it is difficult to get the power from one part of the car to the other and partly because of that mid-engined cars are inevitably rear wheel drive.

Lotus Elise Sport in blue speeding through countryside

But by far and away the bigger and more important reason is that it helps deliver a more sporting experience behind the wheel.

It is not such a problem these days, but not long ago front wheel drive cars tended to understeer, that horrible feeling when you turn the steering wheel into a corner and the car wants to run wide. Rear wheel drive cars can do the opposite, oversteer, which is when the backend feels as if it wants to skid wide on a bend.

Again, neither is a problem in modern cars, but that inherent balance, of the rear end being the more powerful one in determining how the car corners, means that a skilful driver can control and modulate their `line’ through a bend by carefully controlling how much power they put through those back tyres.

It’s fun and feels like you are really in control.

 Four wheel drive (4x4, AWD)

There is only one reason why cars have four wheel drive or all-wheel drive and that is grip.

When you push the accelerator the tyres –the front and back ones – are using the friction between the rubber and the tarmac to put the power onto the road and drive the car.

If it’s slippery, or if they’re trying to move a heavy vehicle up a slope, then the tyres simply become overloaded and cannot cope.  The solution is to spread that load through all four tyres, effectively halving the grip you would need if you have just one end or the other doing the work. These days electronics take over to a large extent and a computer will decide when to distribute the engine power to all four wheels, so in normal road use it is just the front wheels being driven (saving fuel instead of having all four taking engine power) but total traction is available in the blink of an eye if it gets slippery.

VW Passat estate towing a horsebox parked in parkland

Try towing a caravan or horsebox out of a muddy field and you will soon see the benefit of having all four wheels gripping!

It adds weight, cost (in servicing) and complexity, but if you tow it really is the only type of vehicle to have.

Pros and cons:

Front wheel drive

For: lighter, cheaper, more space efficient.

Cons: these days? Nothing, thanks to improvements in handling.

Rear wheel drive

For: can’t be beaten for sports handling, allows a mid-engined design.

Cons: unsuitable for smaller cars.

Four wheel drive

For: the only thing to have for towing or any off-road driving.

Cons: can add weight, take up space and costs more to maintain.

Contact us to find out more about which drive suits you best

Read the rest of John Swift's featured articles