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Spot the Difference Between OE and Aftermarket

30 Jul 2019

Category: Articles

The difference in appearance between aftermarket and OE components can cause technicians to wonder if they are fitting the correct part. However, the reality is that the visible differences result from careful engineering to improve comfort and safety. KYB delves into the differences in appearance between some OE and aftermarket parts.


Many KYB shock absorbers are fitted with a rebound spring. This is a small spring made from alloyed steel, placed around the base of the piston rod inside the body of a shock absorber. The spring acts as a cushion to prevent the bottom of the piston rod from hitting the top of the cylinder during full extension. This prevents damage to the piston rod, increasing the longevity of the shock absorber. It also plays a direct role in ride comfort and safety, working to add smoothness and stability during movements of heightened body roll.

For the majority of vehicles, the OE unit will contain a rebound spring during the first production stage. KYB match this design. However, after the initial production stage, some vehicle manufacturers will remove the rebound spring as a way to help minimise cost. Due to the presence of an extra rebound spring in the KYB unit, the extended piston rod can look up to 50mm shorter.

DID YOU KNOW? There are tools specifically designed to assist with fitting shock absorbers with a rebound spring. Given the shorter length of the piston rod, there may be a need to raise the axle or suspension slightly to attach the shock absorber mountings on select vehicles. These tools compress the internal rebound spring sufficiently to extend the piston rod to the length required to be able to thread the top nut correctly.


Used on many modern cars, the side load spring is designed to eliminate problems with traditional MacPherson struts by using parallel coil springs. A side-load spring reduces the pressure exerted on the piston rod, minimising friction between the piston rod and seal, and prolonging the life of the shock absorber.

After a lifetime of being compressed, the old spring can look very different from its replacement, leading to the misconception that there is an issue with the new spring. However, when compressed, the side load spring becomes parallel, much like a conventional spring.
Given that this spring is often highly stressed, KYB recommends the use of professional gated coil spring compressors. Otherwise, the spring may not compress sufficiently to fit on the strut and perform effectively.


Not only does KYB have a dedicated technical team to assist with any queries, all struts are available to view on the KYB website, with 360° images available for more accurate ordering.

KYB’s ‘Support Zone’ (available at contains useful technical and catalogue information, while their YouTube channel contains a library of over 130 helpful fitting videos.

KYB components are catalogued on MAM Autocat as well as the F:Drive for same/ next-day delivery. Speak to your local representative for more information.

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