Drive trains explained - Do you need 4WD or AWD?

Don’t let car buying jargon get you down. When you’re searching for your perfect motor, we know that you are likely to be inundated with words and phrases that might not make any sense.  

Because of this, we’ve seen that people shopping for their used car are unsure as to whether they want or need 4 wheel drive. Plus, front and rear wheel drive adds confusion to the mix too!

So, if you’re a little confused about which drive train is for you, then go on and have a read.

Firstly

There are a few words that you will need to know before you start reading:

Differential

A differential is the mechanical device that makes the wheels rotate. The position of the differential is what makes vehicles 4-wheel drive, 2-wheel drive, as well as front or rear wheel drive!

Traction

This is the grip between the wheel and the road.

Torque

Torque is the power that the wheel receives from the engine to make it turn.

FWD and RWD

Most cars available to buy are either front or rear wheel drive, and since these are more readily available, you should find out which one will suit you.

Front wheel drive (FWD)

Front wheel drive is more common as the setup tends to be the cheapest to build. This is because the transmission is built into the same unit as the engine. This makes the vehicle lighter and will help fuel economy.

The weight of the differential and the engine will be over the front wheels, which means you’ll have improved grip when pulling away in adverse weather conditions (be mindful that this isn’t as impressive as it would be in 4 wheel drive.)

When accelerating on a dry surface, front wheel drive won’t have as much traction when compared with rear wheel drive. This is because acceleration shifts weight backwards, resulting in less downforce over the front 2 wheels where the power is sent.

It’s worth noting that front tyres can wear quite quickly on FWD cars. This is because they will be working the most under the weight of the unit and differential during normal driving.

The Fiat 500 is a front wheel drive car

Rear wheel drive (RWD)

You will see rear wheel drive more commonly in luxury and sports cars. Mainly because RWD has better acceleration than FWD. It works the same way, but the extra weight is pushed over the rear wheels where the differential is when accelerating and in turn, produces more grip.

But rear wheel drive isn’t great at handling in bad weather. RWD vehicles have a greater chance of wheel-spinning or fishtailing when the roads are slippery. The driving wheels at the back have less weight over them compared to FWD, which results in less traction on the road during normal driving.

But the possibility of fish-tailing is a favourite with petrol heads as it means they can hold a drift with ease!

4WD vs AWD

When you weigh it up, there isn’t a lot of difference between 4-wheel drive and all-wheel drive. But when you want to make a decision between the two, you’ll want to know the fundamentals.

4-wheel drive (4WD)

Modern 4 wheel drive cars give you an option to drive in 4WD or 2WD, (this can be called full or part time.) When choosing full time 4WD, power will be sent to all 4 wheels equally. In part time, the power can be sent to just the front or just the back wheels.

Full time 4WD has better traction as all 4 wheels are being sent power which means they will all have torque. This makes it more likely for at least one tyre to gain traction on slippery, steep and uneven surfaces.

 

The Land Rover Freelander has 4-wheel drive

All-wheel drive (AWD)

You can change all-wheel drive from full to part time just like 4WD. The mechanics make all the difference between the two. In AWD, the wheels are all driven by separate differentials which mans all the engine power can be sent to any one of the wheels if necessary. 4WD is only able to split the power 50/50 between the front and back.

So AWD is ideal for situations where you have low traction. For example, if 3 of the wheels are spinning quicker than the 4th, it would know that those 3 wheels have less traction so the power can be sent to the 4th wheel which has the most traction.

4 wheel drive is more common traditional off-road vehicles such as the Land Rover Defender and the Ford Ranger. All-wheel drive is more common in more modern SUV’s, luxury brands and sports cars. But even today the lines are still blurred on the distinction between the two.

The conclusion

When weighing up the benefits of 4WD and AWD, it’s hard to tell the two apart. They both can send torque to all 4 wheels of a vehicle which increases traction and is better for the winter weather and other adverse conditions.

Ask yourself when you buy a car – are you really going to need AWD or 4WD? We’re not hit with much adverse weather in the UK.

Plus the complex mechanics make AWD and 4WD vehicles more expensive to buy as well as heavier, so your fuel efficiency can be affected. So, if you’re looking to save a few pennies on fuel then FWD or RWD will be ideal.

  • On: 09 January 2019
  • By: Unison Drive

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