Why an unstable car is faster – with the right driver on board

Roger Woodward has posed a question this month that I am often asked. He writes, “Is a driver’s style considered in design? It’s often said Red Bulls are designed to suit Max Verstappen, and the Benettons were designed for [Michael] Schumacher. Is that true? Or is it simply that, as Jackie Stewart once said, the fastest car is ‘always a bitch’? Hence the greats coping and others not.”

I have always wished that we were clever enough to design a car to suit a particular driver. The reality is that you always design a car to give the maximum possible physical performance, which means you design it as light as possible and with maximum aerodynamic performance.

Now, of course, in maximising the aerodynamic performance you need to consider not just the singular numbers that come from computational fluid dynamic simulations or wind tunnel experiments, but the whole gamut of performance at different speeds and different car attitudes.

This means that you must consider how the characteristics of the car vary both at distinct parts of the corner and throughout different speed corners. Consequently, you try to control not just the absolute amount of downforce but also its distribution front and rear, and the suspension stiffness front and rear.

Controlling the vertical stiffness of the suspension will determine the ride heights front and rear and hence how the car traverses the aerodynamic ‘map’. This affects the ratio of front and rear downforce. Controlling the roll stiffness affects the load distribution between front and rear tyres and hence their relative grip.

An F22 Raptor is designed to be unstable – its advanced flight control systems ensure it stays in the sky

Photo by: Senior Master Sgt Richard P Ebensberger / Air University Public Affairs

Generally speaking, a car that is responsive to steering inputs will be faster than a car that is sluggish. We see the same in aircraft. A fighter is capable of very rapid changes of direction that, if experienced by a commercial airliner, would result in some very unhappy passengers.

The fighter, a bit like a racing car, is in competition with an adversary and so the designers will make it very responsive and design to the edge of stability. We try to do something similar with a race car, but the significant difference is that the fighter can use computer control to augment its stability.

In other words, the aircraft is designed to be unstable, and the software ensures it does not either rip itself apart or fall out of the sky. The computer control is agnostic as to the skill of the pilot. It merely takes their input as a directional request and then gives the best and safest solution to this demand.

There is no doubt that as the car is developed the race and performance engineers will try to find set-ups that take the car to the limit of stability that their driver can handle

With a Formula 1 car we cannot use stability augmentation, so we try to develop the set-up of the car to take it to the limit of instability that the driver can handle. This is slightly different to the maximum g-force that the driver experiences.

The pilot of an F22 Raptor can experience 9G aided by a ‘g’ suit and there is no reason, in theory, why a race driver could not manage the same. What is more important is the rate of change of acceleration and the driver’s ability to sense it and respond to it using his steering and throttle to keep the car stable and stop it spinning.

So, while the designer cannot really design a car to suit a driver, there is no doubt that as the car is developed the race and performance engineers will try to find set-ups that take the car to the limit of stability that their driver can handle, and this limit will definitely be driver-dependent.

Schumacher could do things with the skittish Benetton B195 that his team-mates couldn’t match

Photo by: Getty Images

It is also the job of the performance engineers to feed back to the design team where more performance can be found, and so they might well say that a trajectory through an aerodynamic map may be acceptable to one driver but not their team-mate.

It is then up to the design team to see if they can find solutions that push the aerodynamic map in a good direction.

I experienced this when working with Schumacher at Benetton. I was able to take the car into some very unstable configurations as Michael had an uncanny feel for the car and was able to drive it remarkably close to the stability margin. His team-mates found this extremely difficult, particularly in fast corners.

I suspect we may be seeing a similar effect at Red Bull now, where Max’s prodigious talent is able to exploit an unstable car more than his team-mates.

Sometimes it is not just a question of stability. The current generation of cars find maximum performance running close to the ground and this necessitates stiff suspension with the attendant risk of porpoising.

Last season we grew used to seeing the heads of both Ferrari drivers bobbing around at the end of high-speed straights. This is because they were able to handle this, and hence the engineers were able to run the cars stiff and low, gaining performance this way. It may not have been the most elegant solution, but lap time is the ultimate arbiter.

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A bit of bouncing was a trade-off for Ferrari performance last year

Photo by: Ferrari