Progressive Springs

Progressive springs use a combination lower and higher spring rates to achieve the level of travel and ride comfort vs. performance tradeoff that they desire. Car designers must decide how they want the car to ride and handle and in what environment the vehicle will be used and make adjustments accordingly. For example, a luxury car maker will design a spring that is very long in length and has a high proportion of lower spring rate to higher spring rate. This allows the spring to move through a large range of motion and provide a very soft ride without any chance of bottoming out. This is achieved by the soft portion of the spring being the most active. When the suspension encounters a bump the soft portion of the spring is the first to react and absorbs the energy. If a larger bump is encountered, more of the spring will be used until the resistance provided by the spring, matches the energy that is generated by the bump.

When the spring does not have enough resistance to counter this energy, its coils are pressed tightly together and it is said to "bottom out". When this happens the spring rate skyrockets as the spring mimics a solid piece of steel.



Linear Springs

In racing applications, the need for ride comfort provided by a progressive spring, may be outweighed by the need for increased performance. When this happens a linear spring is used. Unlike a progressive spring that increases its rigidity in small increments as it is compressed, a linear spring increases its rigidity exponentially as it is compressed. For this reason linear springs are much stiffer and provide a much less compliant ride than their progressive counterparts. Linear springs can be much shorter in length due to their much higher spring rates. This has the added benefit of lowering the cars center of gravity and also reduces its body roll.