How F1 teams extract the maximum from their tyres

When evaluating a high-performance car's suspension, road testers usually discuss the compromises that must be made between ride and handling. Strictly speaking they should add mechanical grip to that discussion, because a vehicle can handle well but have very low grip - or be well endowed with grip but have dynamics that make it difficult to exploit that grip.

It would be easy to regard ride as the domain of road cars, but while F1 designers are not quite as concerned about occupant comfort as Rolls Royce might be, it would be wrong to say they dismiss it.

It might sound obvious to say a tyre can only grip the road when it's in contact with the surface, but what's less obvious is that the tyre can only produce good lateral or longitudinal grip when it's contacting it well.

Generally speaking this means having a relatively soft suspension - but soft suspensions not only lack the fast response and instant feedback that an F1 driver demands, they're also incapable of supporting the enormous aerodynamic loads experienced by an F1 car at speed. At the end of a 200mph straight those loads are around three and a half tonnes, or the equivalent of six polar bears deciding to hitch a ride.

As always, compromises have to be made. The engineers will try to find a happy medium which keeps the wheels on the ground, gives the driver the feel he requires, and yet doesn't allow the car to be driven into the ground at high speed.

Also, any movement of the chassis on the springs needs to be well damped so the car doesn't continue oscillating once it has hit a bump or a kerb.

The first iterations of this compromise will be made by computer simulation. Equations will be written which describe the motions of the chassis on its suspension when subjected to inputs either at the wheel, usually by bumps, or at the body and what is typically aerodynamic loads.

The simulation will determine what is known as the transfer functions of the suspension, which is essentially a measure of how the suspension transmits forces and accelerations from the road to the hub and from the road to the chassis at different frequencies.

One particular challenge in F1 suspension design is that the vertical stiffness of the tyre is similar to that of the suspension. In other words, if a load pushes the car 20mm closer to the ground then around 10mm of that compression will be in the tyre and 10mm will be in the suspension springs.

The problem here is the tyre acts as a very under-damped spring - something that's very obvious when you see slow-motion footage of a car landing after leaping off a kerb. What physical damping there is in the suspension can only apply to the movement of the spring itself.

In an F1 car this damping usually takes two forms. The first is a conventional hydraulic damper similar to those found on any road car, and which provides a damping force proportional to the speed at which the spring is being compressed. The second is an inerter which provides a restoring force proportional to the acceleration the spring experiences between its two ends.

The inerter is a relatively new device. It generally takes a mechanical form, where the restoring force is generated by spinning a small flywheel with a lead screw, rather like a child's spinning top. Alternatively, it can rely on the inbuilt inertia of a column of fluid which is moved by the suspension.

Many designs have done away with metallic springs and use gas springs instead. These have many advantages. Firstly they can be mounted remotely, perhaps in the sidepod, a distinct advantage in the tight confines of an F1 car.

Secondly, if they are remote they can be connected with a fluid coupling which acts as the inerter, in effect using one component to serve two purposes.

Finally a gas spring is, by the physics that govern it, a non-linear device. That means that the first 100 Newtons of load on the spring will compress it far more than the final 100 Newtons of load.

This means the spring can remain relatively soft at low speeds and loads while having the strength to resist high loads at high speed.

There are disadvantages. Gas springs are sensitive to temperature and so their rate changes as they heat up. This can be compensated for but it's easier just to allow for it. Physics will predict the change.

Even with the non-linearity of a gas spring, it's often necessary to add additional stiff springs to the system that will only engage above the speed of the slow corners. These are equivalent to road car bump rubbers which only engage in extreme conditions and provide a 'helper spring' function.

On top of the ride elements of suspension design, load transfer has to be considered. Many elements handle this as well as the springs, but the primary conduit is the anti-roll bar.

As its name suggests this combats the tendency of the car to roll in a corner, but perhaps more importantly it determines how the loads associated with cornering are distributed between the front and the rear of the car. Since the tyres are very sensitive to vertical load, this roll stiffness distribution has a fundamental bearing on whether the car understeers or oversteers.

Suspension design is also fundamental to the car's aerodynamics: the position and shape of the wishbones themselves play a part in the total airflow management around the car.

The stiffness of the front and rear suspension will determine both how it pitches and migrates through the complex multi-dimensional maps that describe the car's aerodynamic performance.

Perhaps more than any other factor, it's the imperatives of maintaining a stable aerodynamic platform that drive the key decisions in both suspension design and car set up.