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Winter Season Boosts Demand for Steering and Suspension Replacement Parts

It’s nearing the end of winter in the UK, and motorists can expect the combination of salt and grit, together with the legacy of roads still in disrepair since the last season of frosts, to have taken their toll on vehicles. This time around, flooding has been an added complication: aggregates in the road substructure washed away, allowing the metalling to fatigue rapidly and develop cracks and potholes, and missing inspection covers leaving new open or raised ironwork hazards for drivers to negotiate.

Steering and suspension systems inevitably bear the brunt of these challenges, and while this is unwelcome news for car owners, for motor factors it represents an annual upsurge in demand for replacement parts. ZF Services UK Ltd, supplier of Sachs, Lemförder and Boge steering and suspension parts to the aftermarket, considers the effects of winter conditions on steering and suspension components, and which items are most likely to be sought by workshops.

Cold weather embrittlement concerns

The temperatures experienced during a typical UK winter pose no problems for high quality steering and suspension components. This is assuming original equipment (OE) components as factory fitted by the vehicle manufacturer (VM), or subsequently replaced by OE-branded parts such as Sachs, Lemförder or Boge. The alloy compositions chosen and after-treatment processes used in OE parts are designed to avoid the possibility of brittle fracture, and components also undergo testing in climate extremes during development by the original equipment manufacturer and VM.

The story may be different for non-OE aftermarket parts, where ZF laboratory testing has shown that the quality varies widely according to manufacturer. Well-known aftermarket suppliers

and brands with a reputation to protect can be expected to perform reliably, while parts of spurious origin are best avoided from a safety point of view. The uncertainty of materials standards together with unknown production and test regimes could render these more likely to fail under adverse conditions. Common sense should ensure they are denied a place in the stock room racks.

The effect of pothole or kerb impacts

Any heavy impact that significantly exceeds the design load for a component can cause permanent damage, whether it’s from hitting a pothole, repeated kerbing or even negotiating traffic calming measures at too high a speed. Hitting a pothole may be unavoidable, particularly in the dark or if the hole is filled with water or covered by snow. Likewise, colliding with a kerb or verge may prove inevitable on an untreated icy road. Fortunately, high quality OE parts are designed to be tough rather than brittle, so a Lemförder control arm for example would bend rather than fracture under stress, allowing vehicle control to be maintained. Repair of such parts is not possible, so they must be replaced. Typically, control arms, tie rods/track rods and drop links are all susceptible to damage during these minor incidents. Where only a bush or ball joint has been damaged, it often proves less expensive to replace the entire rod or arm, taking into account the time saved (Fig. 1).

Always recommend replacement in axle pairs

Where damage to safety-critical parts does occur, replacement in axle pairs is necessary to maintain stability and safe handling. Aftermarket parts providers can play a vital role in reinforcing this message, explaining that it’s a safety issue and not simply a sales-driven ruse. The performance of a newly-replaced component compared to a worn one can be considerably different, adversely affecting braking distances and handling balance of the vehicle. Any damping variation between a new and a used shock absorber will become all too apparent during avoidance manoeuvres. This is particularly true with the

increasing complexity of steering and suspension designs, where minimising the variation in characteristics between components on each side of the axle becomes ever more critical in maintaining stability.

Don’t overlook sales opportunities in ancillary items

Reminding workshop customers to replace shock absorber spring assisters (bump stops) and gaiters when the shock absorbers themselves need changing is good advice to prolong the life of the new shocks. If the gaiter is worn or damaged, grit and salt deposited on the shock absorber piston rod will abrade the plating, causing roughness and creating the potential for corrosion. This surface damage and/or the grit itself will then tear the piston rod seal, leading to oil leaks from the shock absorber (Fig. 2).

In the case of struts where the new shock absorber insert is unseen, replacing these visible parts can also help to reassure the customer that a thorough job has been done. Sachs and Boge provide Service Kits (Fig. 3) containing spring assister and gaiter for this purpose. It’s a similar story for the top suspension mounts – they should be replaced if looking tired (Fig. 4), and certainly when shocks are renewed, to help absorb impacts without causing damage to the suspension turret or hub carrier.

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