The automotive suspension and chassis industry is highly complex, with different designs used and manufacturing arrangements in place around the world. There is a multitude of political labour issues affecting the industry, as well as the constant battle between the steel and aluminium lobbies to use one material or the other. Companies are also frequently refocusing on ‘core competencies’, resulting in a great deal of change for the industry.

All vehicles need a suspension system to ensure that they provide their passengers with a smooth ride and that the vehicles themselves remain controllable and are not affected by bumps in the road. However, the nearest the average consumer gets to the suspension is when he or she changes a wheel and catches sight of the mechanics within the wheel arch.

Suspension systems have gradually developed over the past 100 years, from a rudimentary (and bone-shaking) system to the modern equivalent that allows vehicles to carry passengers at 70-80mph over great distances – safely and with little driver fatigue.

Electronics have played a major part in vehicle suspension systems for many years, but those electronics have also evolved – to the point where the suspension system’s shock absorption ability and its springing can now be computer-controlled. Up-market vehicles such as the Mercedes-Benz S-class, BMW X7 and Volkswagen’s Phaeton and Touareg are beginning to use air suspension, whereby the vehicle is suspended on computer-controlled columns of gas or oil, rather than coil springs.

Away from the luxury market, the lower-end sector is also undergoing some change, improving vehicle packaging, handling and ride as well as emissions and cost. New materials are coming into play – high strength steels for the springs and anti-roll bars and aluminium for the suspension elements.

But it is not just the materials that are changing –


“new manufacturing processes are also emerging, such as cold forming for springs and hydroforming for suspension members”


new manufacturing processes are also emerging, such as cold forming for springs and hydroforming for suspension members. Less than 15 years ago, almost all vehicles were assembled in-house; now large parts of the vehicle are being contracted out to external suppliers. This often includes the suspension system; the suspension module has arrived.

A definition of suspension designs on European cars
The MacPherson Strut has been almost universally adopted for front suspensions in mass market (A, B, C and D segments in Europe, subcompact and mid-size in the US) cars around the world. This simple, cost-effective design uses a concentric coil spring/shock absorber strut together with a lower wishbone, or A-arm, to suspend the wheel. The name itself is taken from the Ford engineer that invented the system in the 1950s for use on Ford cars.

The lower wishbone can either be a single A-shaped arm or split into two separate, ball-jointed links for greater control and weight reduction, such as the system used in the latest C-class model from Mercedes-Benz. The separate link concept used with MacPherson struts now allows superior suspension control for upper segment vehicles whilst at the same time being less expensive and more space-efficient than the traditional double wishbone system.

Table 1 Examples of vehicle segments

Segment
Region
Examples
A
Europe
Ford Ka
B
Europe
Ford Fiesta, Peugeot 206
C
Europe
Peugeot 307, Ford Focus, Volkswagen Golf
D
Europe
Ford Mondeo, Opel Vectra, Nissan Primera
E
Europe
BMW 5 series, M-Benz E-class, Audi A6
Sub-compact
North America
Hyundai Elantra
Mid-size
North America
Honda Accord, Toyota Camry, Ford Taurus
Full-size
North America
Lincoln Town Car
Source: just-auto.com

Four-wheel-drive vehicles have traditionally used rigid, ‘live’ front and rear axles, suspended by multiple bar links to provide high strength and sufficient wheel articulation. The emergence of the sports-utility vehicle (SUV) has seen a major switch to independent suspension systems in order to provide the car-like handling that consumers now expect (although it also comes with the loss of some off-road ability). These have been developed to such an extent that models such as the BMW X5 and Mercedes-Benz M-class now use MacPherson strut, double wishbone and multi-link front and rear suspensions.

BMW X5 suspension components
Source: BMW

In Europe, the suspension and chassis industry is very complex. It consists of many Tier 2, 3 and 4 companies that all produce a certain component – whether it be an anti-roll bar, steering knuckle, suspension arm, coil spring or air spring. However, in recent years, the so-called Tier 1 suppliers (those companies that source components from all the lower tiers in order to supply directly to the vehicle manufacturers) have begun to alter their strategy. Now, the Tier 1 suppliers have started to specialise in systems, integrating value-added products into modules for the vehicle manufacturers.

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The Tier 1 companies have created new companies that produce one special (usually large or expensive) chassis part that is able to act as the centrepiece of a chassis or suspension ‘module’. The Tier 1 company outsources all the smaller, cheaper components from the lower tier companies and then assembles them into a module. This module is then ready to be bolted into the car on the production line, saving the vehicle manufacturer time and, crucially, cost of storage and supply logistics of all the smaller components.

This is a growth industry in Europe but even more so in the US and emerging markets such as Thailand and South America. A number of Tier 1 companies have emerged and are beginning to shake up the industry by buying up smaller companies. Small companies have also joined forces to pool their resources and expertise in order to become a full system supplier. Independent (not modular) suppliers still exist in many areas and in all car makes, but modularity is becoming quite a momentous force.

However, the industry has recently had to rethink its module strategy – the module suppliers are not experiencing the growth that they expected in Europe. Admittedly some large, well-known companies are achieving a degree of growth, ZF in particular, which has achieved significant growth in suspension and chassis modules for the Mercedes-Benz M-class in the US and a number of other vehicles. Benteler has also done very well, particularly with the Ford group on a worldwide basis.