Mythbusters: Rear-wheel drive cars don't understeer

Jason/Jun 25, 2020 01:39 PM

Yes, understeer, in a RWD car.
Photo credit: ebay

Rear-wheel drive (RWD) motoring brings with it an untold amount of joy. They’re inherently well balanced, steering feel doesn’t get corrupted, and best of all, you can oversteer to your heart’s content. You hear driving ‘purists’ rave on and on about the benefits and satisfaction a rear-wheel drive car can give you.

One of the many joys of RWD motoring, oversteer.
Photo credit: DriveMag

However, I have had such ‘purists’ tell me before, the reason why they like RWD cars is because “they don’t understeer.” Now, this is patently untrue. Cars of any drivetrain layout can and will understeer if you do the wrong things.

Photo credit: Whiteline

Understeer basically means that your front tyres have lost grip and will not respond to your steering input anymore. When a car understeers, the car will plough on straight towards the outside of a corner. Understeer is a bane to people who love driving, just ask any racing driver.

There are a few factors that would cause a car to understeer, regardless of it being a front-wheel drive (FWD) or RWD. Let’s dive into it and see what situation and conditions can potentially effect understeer in a car;

Video credit: Mischief TV

1.) Excessive speed in a corner: Understeer also happens when you carry too much speed into a corner. Your front tyres have to contend with longitudinal and lateral forces. Carrying too much speed into a corner impedes a tyre’s ability to turn. This is because, in the battle for tyre grip, longitudinal grip will always win over lateral grip.

So, what do you do when you’ve barrelled into a corner too fast and feel your steering going light with understeer? You scrub the speed down by lifting off the throttle. If the front wheels still wouldn’t turn, try braking smoothly till you can feel your front tyres gripping again. If all else fails, stand on your brakes and pray. Watch the video above from 00:19 (slo-mo at 00:34) to see how too much speed causes understeer.

Video credit: CARBÄHnM3 Production

2.) Excessive or rough steering input: Many drivers use too much steering for a particular corner, or are too rough with steering input. Remember, your front tyres (in a RWD, at least) have a finite amount of grip to decelerate and turn.

You overwhelm the grip of the front tyres when you turn the steering too much, or too suddenly. The worst part is, having already caused understeer by turning too much, some make the mistake of turning the steering even more (watch the video above from 00:38).

The solution is rather straightforward; be smooth with your steering input. Learn and practice to feed your steering progressively (placing your hands on the 9 & 3 steering wheel position helps immensely). That way, your front tyres always have enough grip to respond to your steering input. Plus, your passengers will thank you for being such a smooth operator.

Straighten your steering wheel before accelerating out of a corner

3.) Accelerating too early/too hard in a corner: So, you did the first 2 things correctly, heading into a corner with the right amount of speed and steering. Then, in the middle of the corner, you jump on the power a smidge too early, or too hard, and you feel understeer set in again. Applying more power will make it even worse. This happens because, every time you accelerate or brake, your steering performance is reduced (remember, finite amount of grip for longitudinal & lateral forces).

The key here is to be patient in the cornering phase, feather the throttle lightly and wait for your steering to straighten out before applying more power, and feed it in progressively (notice this theme throughout?).

So, the next time someone tells you RWD cars don’t understeer, tell them otherwise. It’s only partially true that FWD cars are more prone to understeer because of its inherent weight distribution (more nose heavy), and the fact that the front tyres of a FWD car has more forces to juggle (acceleration, braking and steering) as opposed to a RWD car. Ultimately, yes it’s a myth that RWD cars do not understeer.

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