The suspension for the McLaren MP4-12C breaks new ground, offering hitherto unseen levels of roll control and grip – an almost flat cornering attitude, depending on the programme selected.
Although such track-like responses would normally imply a rock-hard ride, the 12C delivers compliance and ride comfort more akin to an executive saloon car. The mix of occupant cosseting and sporting potential is truly unique. The 12C offers the driver both class-leading ride comfort and class-leading performance.
The whole chassis package produces not only a unique relationship between ride and handling, but also astonishing lateral grip and outstanding traction. The 12C is poised and balanced whether negotiating high or low speed corners, during direction changes, under heavy or light braking and on tightening or opening corners.
The trick behind blending such opposing objectives lies in the innovative Proactive Chassis Control system, uncompromised geometry, and weight distribution.
The suspension is based on double wishbones with coil springs. The dampers are interconnected hydraulically and provide adaptive responses depending on both road conditions and driver preference.
The Proactive system features adjustable roll control which replaces the mechanical anti-roll bars that have been a standard feature of road cars since time immemorial. It allows the car to maintain precise roll control under heavy cornering while decoupling the suspension in a straight line for excellent wheel articulation and compliance.
There are three suspension modes that are selected on the Active Dynamics Panel. As with the powertrain adjustment, there is a ‘normal’, a ‘sport’ mode and a high performance mode which adjusts numerous parameters in the system.
Not only is the Proactive suspension a unique application that delivers absolute benefits to driver and passenger, but it is also another example of McLaren’s drive to achieve all-round performance goals from core engineering targets.
For example, the unique blend of a compliant ride with ultra-sharp handling also delivers ownership benefits as it protects suspension bushes from wear and tear, with McLaren’s research suggesting a potential for up to ten times more mileage than on some competitor cars. Also, the hydraulic pump that supports the dampers is the same pump that supports the electro-hydraulic steering system. Why use two pumps when one - small and lightweight - pump will do?
The engine is mounted low down in order to lower the centre of gravity while the radiators are rearmounted and reduce weight by saving on long piping to and from the engine (and the fluids they would hold). The value of rear-mounted radiators is key to the 12C’s handling and balance. The more weight that can be concentrated within the wheelbase and towards the centre of gravity, the lower the polar moment of inertia, thereby improving corner turn in.
Another feature that helps the 12C to handle at a new level is a development
of an electronic system used by McLaren’s 1997 MP4/12 Formula 1 car, – Brake Steer. In essence, it is a system that brakes the inside rear wheel when the car is entering a corner too quickly to
make the desired radius. Under normal circumstances the front would wash away wide of the apex the driver wants to touch: in other words, the car is in a state of understeer.
Brake Steer manages the tendency of a car to wash out and brings its nose back on line. It assesses the steering angle to determine the driver’s intended course and applies the inside rear brake to increase yaw rate and resume the desired course.
The system also works on acceleration out of a corner when the inside rear has a tendency to spin, allowing the driver to put power down more quickly. It controls what a limited slip differential would do and obviates the need for such a complex and heavy unit, thus saving more valuable kilos.
The standard brakes for the 12C reduce overall vehicle and unsprung mass. McLaren has developed a composite braking system that uses a forged aluminium bell that attaches to the cast iron disc. This solution maintained the excellent brake feel of a cast iron disc while saving 8 kg. Carbon ceramic brakes will be available as an option, offering fade-free braking performance during high performance driving, but the standard composite brake system is actually lighter than the larger carbon ceramic units.
The design of the standard cast alloy wheels (19” front, 20” rear) was driven by McLaren’s light weight objectives: the light weight styling was agreed in concept, then the wheel was tuned using Finite Element Analysis to take a further 4 kg out of the wheels. Bespoke Pirelli tyres have been developed in conjunction with McLaren specifically for the 12C.
An array of electronic aids is fitted to the 12C that will assist and protect the less-experienced driver, or when conditions challenge even the best. These include ABS, ESP, ASRtraction control, Electronic Brake Distribution, Hill Hold and Brake Steer. The level of intervention varies according to the handling mode selected.
Source: Official press release - Sept. 9th 2009.
