It’s a common saying that front-wheel drive (FWD) cars tend to understeer, while rear-wheel drive (RWD) cars are prone to oversteer. But that is a generalisation, as witnessed from the two crashes happened on the same Sunday morning yesterday (16-April) on the road towards Genting Highlands.
Ironically, the car that oversteered is a FWD (Honda Civic) and the one that understeered is a RWD (Toyota Mark X).
Any car, regardless of its driven wheels, can be engineered with a tendency to understeer or oversteer at cornering limits. Tyres have a given amount of traction irrespective of the direction of force applied. This is often referred to as the traction circle.
One of the fundamentals of performance driving is to use weight transfer to maximise the traction circle. Braking transfers weight to the front, increasing traction at the front end, which will in turn decrease traction at the rear.
This was observed from the accident involving the FD-generation Honda Civic. The car can be seen carrying considerable speed (the digital video recorder footage showed a peak GPS speed of 101 km/h before the corner, and that’s on the camera car) into the left-hander and braked mid-corner, upsetting the balance of the car.
In such scenarios, vertical load on the rear tyres will be reduced and depending on how much traction is available, the rear tyres could loosen their grip, which is what happened in this case.
Remember this rule of thumb – brake in a straight line. That means braking well before the corner if you’re carrying excess speed. There is the topic of trail braking, which is an advanced technique to brake later and get better rotation, but that shall be discussed in another day.
If you absolutely must brake mid-corner, pay attention to your steering input and be extremely finessed in your braking. As long as you’re not at the cornering limits of your car, there will still be some leeway for load transfer. Modern cars with stability control will help you sort things out, to a degree.
The next crash involved a second-generation Toyota Mark X. Again, the car can be seen carrying excessive speed into the turn and ploughed into a tree. Thankfully, no other motorists appear to be involved based on the footages of the two crashes.
Carrying too much speed into a corner impedes a tyre’s ability to turn, which is the primary cause for most cases of understeer. This is due to longitudinal grip taking precedence over lateral grip in the competition for tire traction, regardless of the drivetrain arrangement.
Photo credit: Whiteline
So what should you do when you experience understeer? If it’s mild, simply lift off the throttle. While is this counter instinctive, do not turn the steering wheel even more. Straighten the steering wheel ever so slightly to an angle that the tyres can start gripping again.
If there is still too much speed, apply brakes smoothly until you can feel the car turning as intended. And if all else fails, stand on your brakes and pray.
Everything that was mentioned here applies to both FWD and RWD cars. FWD cars are not impervious to skidding and RWD cars aren’t made to oversteer by default. If you drive in a ham-fisted way, no amount of weight distribution or driven wheels will prevent you from losing control.
Drive safe, folks. If you wish to test the capabilities of your vehicle, do so in a secure and controlled setting such as track days or closed courses. When driving on public roads, never go all out.
The quest for automotive knowledge began as soon as the earliest memories. Various sources information, even questionable ones, have been explored including video games, television, magazines, or even internet forums. Still stuck in that rabbit hole.
