Kilen Wire Coil Springs

What’s the Difference Between Parallel and Tapered Wire Coil Springs?

Kilen explains coil springs, their quality features and some fitting tips for performance. Find out more about the difference between parallel wire and tapered wire coil springs.

Kilen has one of the industry’s most extensive ranges of coil springs. All springs are manufactured in Kilen’s own factories to ensure full control over availability. Kilen offers both parallel wire (constant thickness) and tapered wire (thickness of steel reduces toward each end of the spring) coil spring designs to offer installers a choice based on their needs.

Parallel vs. Tapered Wire Coil Springs

Some original springs are manufactured using tapered spring wire in order to save weight. However, as tapered wire springs are exposed to almost identical stresses throughout the total length of the material, thinner wire coils towards each end can experience stresses as high as those in the most active part of the spring. This can increase the risk of premature spring failure, and is often aggravated by corrosion at the end (transition) coils.

In order to remove this risk of premature failure, Kilen springs are made from parallel spring wire, where the steel has a consistent thickness (diameter). As a result, a Kilen spring may need to be slightly shorter than a tapered wire OE. It is designed to fit the application and once fitted, it will provide the correct spring rate and ensure that the vehicle sits at the correct ride height.

Measuring up Progressive Spring Rates

There is a popular misconception that progressive spring rates can only be achieved by tapered wire springs, particularly those with a minibloc design (rugby ball shaped). However, parallel wire springs can also be designed to have linear or progressive spring rate characteristics by varying the pitch (gaps between the coils).

Tapered Wire Coil Spring
Tapered Wire Spring
Parallel Wire Coil Spring
Parallel Wire Coil Spring

Coil Spring Fitting Advice

As safety critical components, it is important that coil springs are fitted properly. Below are some popular applications that installers should be aware of.

Ford C-Max, Focus II; Mazda 3; Volvo C30, C70 II, S40 II, V50

When replacing front coil springs on the aforementioned vehicles, it is important to ensure that the top spring plate is correctly lined up with the shock absorber.

Coil Spring
After locating the top pin, position the strut top mount so that the top pin aligns with the bottom pin.

Volvo S40 (5/00-12/03) and Volvo V40 (5/00-04)

When replacing front coil springs on the above vehicles, it is important to install them the right way up. Incorrect installation c an cause the spring to bend, or move out of position and rub against the bodywork.

Coil Spring
The end with the smaller pitch should be installed in the top bearing whilst the larger bitch should be installed in the bottom spring pan.

All Kilen parallel wire coil springs come with a 3-year warranty whilst the tapered wire springs come with a 2-year warranty. Catalogued on the F:Drive and MAM Autocat, speak to your local FPS representative for more information.

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If you have an account with FPS and would like more information on this article please get in touch with your local warehouse or Territory Manager, alternatively use our enquiry form.