4th Quarter 2014: How it’s Made

Coil Spring TESTING


Which two are the same?


Correct Answer: None

Coil Springs may all look alike when assembled but there’s big differences in how they perform and how long they might last. For a spring to qualify and become part of a KYB Strut-Plus it must pass a series of rigorous tests: Endurance, Variable Strength Rates and Installed Height are some of them.

In the picture above, if you guessed that the two outer springs could be the same, take a closer look: They are wound two different directions. None of the three will work the same. All three are from non-KYB brands of complete assembly’s that catalog them for the same vehicle and corner position. So which one is the correct one for the vehicle? Well, there’s no way to know for sure unless you test them against OE specs. That’s exactly what KYB does.

Coil Spring Testing-1

Endurance testing can reveal a spring’s quality. In the pictured example is a spring candidate that didn’t make the KYB grade. For this passenger car application it needed to survive 200,000 full travel cycles and at varying speeds. In a KYB R&D center, an engineer fits the spring onto a test bench. Then a computer controlled hydraulic press pushes against the spring and can recreate driving conditions. To speed up what could take years of testing into less than a week, the OE specs use full travel limits that exceed any possible driving condition. This spring failed at less than 23,000 cycles.

Even when a spring meets KYB engineering requirements like corrosion resistance, extreme temperature operation and passes endurance testing, it’s still not a member of the Strut-Plus team. It has to be assembled with a KYB Excel-G strut and installed on the target vehicle to be sure it fits properly and provides the correct ride height.

The last step may be one of the most important… We road test it thoroughly. That way when you install a KYB Strut-Plus you can be confident that it will perform the way the manufacturer intended… Correctly.

Another example of how KYB builds OEA; Original Equipment for the Aftermarket.