Julian Edgar, 50, has been writing about car modification and automotive technology for nearly 25 years. He has owned cars with two, three, four, five, six and eight cylinders; single turbo, twin turbo, supercharged, diesel and hybrid electric drivelines. He lists his transport interests as turbocharging, aerodynamics, suspension design and human-powered vehicles.
When technology doesn’t always makes things better.
I am not a fan of oversteer. In any typical real world, real road, real driver situation, it’s more dangerous and harder to control than understeer. And obviously the vast majority of car companies agree with me because with very few exceptions, all cars that are sold today lean towards understeer as their final handling trait.
But perhaps that statement should be analysed a little – good things need to occur in moderation.
Rear wheel drive cars that handle well can almost always be power-oversteered, so a car like a Mazda MX5 has slight turn-in understeer and slight power oversteer. Good front-wheel drive cars have power understeer and slight lift-off oversteer – something like a Peugeot 206 GTi or 307 for example. Four-wheel drive cars typically have turn-in and power understeer, although really brilliant examples like the Evo 7 Lancer can alter this to turn-in understeer with little exit power oversteer.
So, while the situation is a bit more complex and subtle than covered by this blanket statement, it’s a fact that most standard cars – when pushed past the limit – understeer. If the designers have the choice between neutral, understeer or oversteer (and of course they do have that choice!), then they have nearly always gone for neutral-followed-by-understeer. It makes cars safer and much more user-friendly. And that’s a good thing – it saves lives.
But some important aspects of that situation are changing. How? Well, with each of the (very good handling) cars that I’ve nominated above, the driver has an input into the handling characteristics – he or she can use the throttle to edge the car into the handling trait that’s desired. (Like the throttle lift in a front-wheel drive to get the tail happening, or less throttle in a constant four wheel drive to diminish the understeer on a corner exit and so make it more neutral.) So it’s understeer that can be tweaked, if you like.
And this change? With the electronic systems that are now being introduced, some manufacturers are choosing to remove those options. Take stability control, for example. One of the biggest breakthroughs in vehicle dynamics in decades, stability control senses whether the vehicle is following the driver’s desired cornering line. If the car isn’t, individual wheels are braked to swivel the car back onto line. So, if the car is negotiating a corner and is understeering, the inside rear wheel is automatically braked, pivoting the nose around. If oversteer is occurring, the outside front wheel is slowed. The car’s cornering attitude can then be made neutral – virtually right up until the point where the grip of three wheels is completely lost.
In the front-wheel drive Mercedes A-Class the affect of stability control is pronounced. As I wrote in our A-Class test, "One of the best ways of experiencing the behaviour of ESP [Mercedes speak for stability control] is to accelerate around a large roundabout. As the front loses traction, the ESP launches into action, the series of discrete rear braking applications pulling the nose around forcefully each time the understeer becomes excessive."
In that case, the stability control is used to return a power-understeering FWD car to a neutral handling attitude.
In my own car – a ’98 Lexus LS400 – stability control is used in a similar way – pulling back understeer to make the car handle more neutrally. (It can’t power oversteer because the traction control shuts down wheelspin. The action of the two systems can easily be separated, because when stability control is active a dashboard warning beeper sounds. Traction control just flashes a light.)
And with a neutral-handling car being the stability control engineers’ aim, you can still have a lot of fun driving these cars. After all, subtleties of over- and under-steer are still there, with the stability control electronics helping you along.
But maybe not for much longer. Recently I have driven no less than three new cars where the stability control has been set up to create not a neutral handling car – but one with plenty of understeer. And I am not talking about ‘good’ understeer – where there’s just enough to settle the car and at the same time tell the driver to get their act together – but instead plough understeer of the sort that on a roundabout takes the car across two lanes of shrieking front-end rubber.
It appears that in tight conditions, the stability control in these cars has been software engineered to actually create a car with a lot of understeer. (And the cars? The Lexus IS300, Audi A4 3-litre FWD, and the Audi Allroad.) And I may prefer under- to over-steer, but a car that does neither until the complete limit of grip is reached is a helluva lot better…
Think: who cares about stability control?
Think: I never drive these sort of prestige cars anyway?
Well, think again. The base Merc A-class is stickered at just AUD$35,000 – a reflection of how little it costs to add stability control to a car already equipped with ABS. You can expect to see stability control in the Australian carmakers’ local line-ups well inside 18 months – and just as ABS has, stability control will trickle down to all models.
So how will the local designers handle it? Will stability control be used to make a car more neutral in its handling, dialling out both understeer and oversteer? Or will they plump for the electronics to deliberately create understeer? The four-wheel drive Holden Commodore is tipped to use three open (ie non-LSD) diffs, so the torque split will be likely under the de facto control of a stability control system. (Brake one wheel and the torque has to go to the other three. Brake two wheels and the torque goes to the other two – you get the picture.) Making a car that is neutral when lots of throttle is being used (or alternatively an understeerer) will be as easy as changing some software code. Which way will they go?
The FWD Magna is sure to get stability control in the near future. They’ll be aiming at dialling-out a lot of the power understeer – but will they maintain the cast-in-stone philosophy that Australian Mitsubishi engineers seem to have that a FWD car should never oversteer… no matter what is done with the throttle? Setting up the base suspension of the Magna with much greater rear roll stiffness could easily revolutionise the turn-in and mid-corner grip of the car – and then they could use the stability control to control the greater propensity that the car would have for lift-off oversteer.
The current highest performance Australian Fords are sold with none of these types of electronic assists at all – not even traction control. When stability control is fitted to the next round of hi-po Tickford models, will the philosophy rest firmly on the driver having control of a neutral handling car – or will the pendulum swing so far the other way that any cornering attitude will immediately be shut down?
The answers to those questions will determine to a very large degree what the cars are like to drive hard… and these software decisions must be being made right now.
One thing’s for sure. Whereas stability control was initially seen as a means of making a car more neutral in its handling behaviour, some manufacturers now seem to have plough understeer as the endpoint aim.
And while I might prefer understeer to oversteer, I don’t have any liking at all for ploughing…
