BTCC VECTRA SUSPENSION

Body Shell | Aerodynamics | Engine | Transmission | Suspension | Interior

		The suspension can be the making of a successful Touring Car as it defines the way the car behaves on the track. Equally, poor basic suspension geometry can render a car useless. The goal of the suspension designer is to maximise the car's mechanical grip and this is done by controlling the movement of the wheel to ensure the tyre has maximum contact with the track. The current regulations require that the layout of the suspension on the race car is very close to that of the road car, which will have been designed for a completely different set of conditions. However there is still scope for countless combinations of suspension settings to be analysed to tailor the design to suit the extreme conditions of track racing. Before the design process starts the existing suspension is analysed. The design and layout of modern suspension systems varies enormously between manufacturers and ranges of cars and it is important to fully understand how the suspension behaves before determining how it can be changed to suit our needs.
Suspension is designed to fit close to the road car mount points

The starting point for designing a Touring Car suspension is to optimise all static settings within the TOCA regulations. It is these regulations which constrain exactly what we can do to the geometry of the suspension. Firstly, the track of the car can be increased within the specified tolerance to increase the stability of the car.The points at which the suspension attaches to the chassis can all be moved by a maximum of 20 mm.

Even within this small distance some significant changes in the behaviour of the suspension can be achieved. The positions of the points which attach the suspension links to the hub of the wheel can also be moved and it is here where the major gains in performance can be achieved.

It is important to consider not only the static set up of the suspension (camber, castor and toe) but also how these parameters change through the full range of movement of the suspension and 20° of steering lock in each direction. Furthermore, to optimise the set up for a particular track and track condition, all these parameters must be adjustable if at all possible.
If we then take into account a range of different springs for the front and rear of the car and an infinite number of configurations for the dampers it is easy to appreciate that the job of the suspension designer is not an easy one.

Experience gives us a rough idea of where to start with the geometry of the suspension but with the aid of our CAD software, we can explore the relative merits of many different designs without actually putting pen to paper. It is vital to keep in mind, during this stage, that all the new suspension components plus lightweight brake discs and racing brake callipers (4 pot front, 2 pot rear) must be packaged into the confines of a 17" racing wheel rim.

The next stage is to transpose the information generated so far into our dynamic modelling software where each component can be simply modelled in the computer and put through its paces. Loads and articulation can be simulated simultaneously and the effect on every component analysed to provide us with enough information to start the design process.

All our components are modelled in 3D on CAD software in order to provide a component that is easy to manufacture and fits into its environment at the first attempt. All rubber suspension joints are replaced with steel spherical bearings to ensure that the lost motion in the system is kept to a minimum and that all the suspension loads are transmitted through to the stiff chassis. The uprights, which hold the TOCA specified hubs and wheel bearings and our own Penske 3-way dampers, are machined from a solid aluminium block. The load bearing components such as the uprights and wishbones are subjected to Finite Element Analysis to ensure that they can withstand the extreme conditions of Touring car racing. At the rear of our car the single beam axle must be extremely strong and stiff when loaded in one direction but flexible in another. Cornering and braking loads in the BTCC can approach 2g (approximately 1 ton of sideways load at each corner) and shock loading from kerbs and collisions can increase these loads by up to 300%.
		Dampers are tested on our Damper Dyno

The dampers affect the speed at which the wheels travel up and down the with bumps in the track surface. The characteristic of the travel of the wheel through the range of suspension can be adjusted in three ways. The "low speed" adjustment affects the car in cornering and braking, "high speed" adjustment alters the way the car behaves over kerbs and bumps in the track and the rebound adjustment governs the way the wheel travels away from the body of the car when the suspension is unloaded. These are combined to get the wheel to hug the ground and to keep the car stable and controllable at all times.

The suspension is now designed and the race engineer is presented with enough adjustability in the geometry to optimise the performance of the car within the regulations. Our dynamic modelling software now enables the engineer to model all four corners of the cars suspension on a computer and simulate track conditions before we get there. The rest is up to the driver.