Coil spring for your car

Tough damping for comfortable driving: coil springs

Coil spring is an essential part of the suspension, together with the shock absorber providing comfortable damping. A high-grade coil spring compensates the unevenness of the road and prevents it affecting the passenger cabin. The coil spring is the most common form of mechanical damping.

Why both shock absorber and springs?

Springs of a car compensate the larger road bumps. Being pre-tensioned they press the wheel into every hole it passes over, causing the car to maintain a permanent contact with the road. The shock absorbers in their turn are built for the smaller surface irregularities and reliably damp the stones and smaller holes in the road. The shock absorber and coil form the suspension strut. Their damping functions are always exactly tuned. When the shock absorber is replaced, it must always match the coil spring.

Different suspension systems

The very first suspension had leaf springs, which were installed in coaches. Leaf springs are nowadays rarely found in cars. Off-road vehicles and vans might still have them on their rear axle, although they are gradually being replaced by coil springs. Another type of suspension can be found in tracked vehicles. Here, the torsion bar has proven itself as an adequate suspension element. Especially compact or mid-size French cars were equipped with this type of suspension. Technically, torsion bars were very simple: a steel bar, twisting along its longitudinal axis. Its installation is rather complicated and in family cars it has a strong tendency to rust and jam as a result, making its replacement more even more difficult.

Position of the coil spring

Generally, the coil spring and the shock absorber form the suspension strut as a unit. On rear axles, separate constructions can be found with spring and shock absorber at different positions. Two constructions for suspension struts are common: in most struts, the shock absorber is situated in the centre of the coil spring. Some struts have the shock absorber and coil spring sitting side by side. They can be replaced in one go as one piece, just like normal struts.

Defect of the coil spring

A coil spring lasts ca. 100.000 – 150.000 km. The weak point of the component is its construction. In order to be sufficiently sturdy for a long service it can on no account be corrosion-resistant. Stainless steel is too brittle for this task and would break too soon. The manufacturers equip coil springs with elastic protection paint. The close contact with the road and the continuous movement on its fixing point causes the protective paint to grind off gradually. Rust develops and the spring can break sooner or later. A broken coil spring is synonymous to a dangerous driving situation. It is therefore advised to check and if necessary replace the coil springs at the prescribed intervals. A broken spring has an immediate negative impact on the driving quality. The car pulls to one side, the suspension is very noisy and the steering is badly impaired. If this occurs, you should immediately drive to the closest garage.

Replacement of a coil spring

Disassembling a defective coil spring is easy: it can be cut with a grinder and removed. This is the safest way, too: a broken coil spring can rupture again in the spring compressor, potentially causing a life-threatening situation. The entire suspension must be disassembled to install a new coil spring. Installing a new coil spring always requires the use of a spring compressor. All makeshift attempts with tension belts or other compromise solutions are very dangerous. Actually, a large amount of serious accidents during privately conducted car repairs are the result of compressing springs with unsuitable tools.

Costs for a new coil spring

The price for a coil spring depends on the car in which it is installed. Light and compact cars need less strong coil springs than heavy limousines or high-performance racing cars. Coil springs are always replaced per axle. Prices start at ca. 30 EUR (c. £27) per piece.