Strut your stuff

SUPLEX, the coil-spring specialist, joins forces with the German steering and suspension expert OPTIMAL to apply some German know-how to the UK aftermarket.

Mechanics all over the UK will have had a busy time replacing broken coil-springs during the first quarter of 2009. The reasons for the ramp increase in sales are clear to Andrew D. Graham, Managing Director of SUPLEX GmbH in Germany: "There are several contributory factors but the primary cause is the harsh winter of 2008/09. This brought ice, snow, cold temperatures and salt to Britain´s roads. The coil-spring/coil-spring seat interface is often badly designed, allowing road debris to collect around the bottom coil. Water and salt mix with the road debris, forming a grinding paste which causes accelerated corrosion of the coil-spring in this area. A sudden impact to the suspension, caused when driving over a speed bump or off a kerb, can cause coil-spring breakage, especially in very cold temperatures."

Additional benefit

A significant of number of small and medium-sized passenger cars are fitted with "side-load" or "banana" springs on the McPherson strut. These springs are curved; they only straighten out when subjected to a load. Most side-load springs are cold-coiled from pre-hardened spring steel. These springs are popular with the vehicle manufacturer because the help to reduce the frictional forces between the piston rod and seal in the shock absorber. The benefit is twofold: firstly, the life of the shock absorber is extended and secondly, the shock absorber has better response characteristics, especially in the low seed regime. An additional benefit is the relatively small spring body diameter which improves suspension packaging.

New problem

There are two major disadvantages of this type of spring. Durability, in a harsh, underbody environment is limited and also the inherent difficulty of fitting a curved spring to a straight shock absorber. Mechanics everywhere will be familiar with this new problem. Coil-spring replacement has always been a potentially dangerous task but fitting a curved spring increases the complication - and therefore the risk - even if the mechanic has access to professional equipment. SUPLEX has recognized this problem and together with OPTIMAL, introduced a brand new range of pre-assembled McPherson struts for popular applications. Andrew comments: "We have concentrated on vehicles which appear to have an inherent coil-spring problem. In most cases, these vehicles are equipped with a side-load spring. What we are really offering, therefore, is a significant time saving for the mechanic and less likelihood of injury whilst performing the repair.

"The engineering departments of both companies have worked hand-in-hand to produce a product the mechanic is going to love to fit.

Everything required to complete the repair, including detailed instructions, is contained in the kit. Nothing has been omitted, our engineers really have given consideration to every single issue."

Repair delays

Concerns that replacing the entire strut instead of only individual components can result in an unnecessarily expensive repair are unjustified, according to Andrew, he says: "The spring, shock, bearing support and mounting kit work together as a unit, they are subjected to the same wear and tear. If only one of these components are in less than perfect condition. A good mechanic will always inspect all the components after stripping the strut to replace the spring. If other components are found to be defective, replacements need to be ordered. This delays the repair further.

Additional components

By fitting a complete strut, the mechanic can be sure all individual components are new and correct for the application. The reduction in repair time is significant and the reduced labor charge can, in many cases, offset the cost of additional components. The advantages for the mechanic are obvious - more workshop throughput, an easier repair and a satisfied customer. "The current range numbers 50 applications but this will grow to 80 by the end of the year. The program is very much example, pre-assembled struts for: Citroen C3, Fiat Punto, Stilo, Ford Ka, Fiesta, Focus, Mondeo, Mercedes-Benz A-Class, B-Class and Smart."