HD Progressive Rate Vs Constant Rate Springs

Today's topic of discussion is the rear spring options that we offer with our kits, and how to choose the best one for you.

There are two types of coil springs - progressive (variable) rate and constant (linear) rate.

Constant Rate - This spring type does not change spring rate as it's compressed.  If we consider, for example, a 350lb coil, it would take 350lbs to compress the coil 1", 700lbs to compress the coil 2", 1050lbs to compress the coil 3", etc.  They have the same spacing between the windings of the coil and the diameter of the wire remains the same throughout the entire coil.  This is by far the most common OEM Ram 1500 rear coil, although a very small amount of OEM progressive rate coils do exist.  With a constant rate coil, you have a tradeoff to consider when designing - do you make the coil soft to prioritize ride quality but lack weight carrying ability, or do you make the coil stiff so it can haul weight, but will ride poorly as a result.  When designing the OEM coils, Ram clearly chose the first option.  The factory coils ride nice but are very soft and tend to sag when only a small amount of payload or hitch weight is added.  This is the normal rear coil that comes with our kits if you don't choose to upgrade the spring.  If you never plan to tow or have more than 300lbs in the bed of your truck, this spring is an acceptable choice.

Progressive Rate - This spring type is designed to have an increasing spring rate as the spring is compressed.  In laymans terms, it can be designed to be very soft for the initial few inches, but it will get stiffer as weight is added.  This is ideal for almost all scenarios and is a superior design to the constant rate spring.  The first part of the spring is soft to prioritize ride quality, but if you add weight to the truck, the spring will compress and get stiffer to help handle the weight.  Because of this design, you won't lose any ride quality by choosing a progressive rate spring.  Our +35% capacity rear coil spring is a progressive rate spring and this is the coil that we recommend for any customers who tow or haul, or those who think they may do so in the future.

If you have any questions about selecting a spring for your kit, send an email to brendan@airdelete.com or check out our FAQ here.