The third spring first circulated among the CART circuit back in the early 90s. I think it was the guys who worked for THE CAPTAIN who first toyed with the idea about a ride height control for the cars at high speed. Downforce is a function of speed, and naturally the faster you go, the more DF you produce.
The more DF you produce therefore, the easier it is to compress the car into the ground, causing the car to bottom and if the bottoming happens on a high speed corner, then it really isn't a pleasant experience. So to counter that, you have to run stiff corner springs But the catch is, the stiffer springs you run (in real life), the faster your tires get destroyed and the level of mechanical grip is hindered severely, causing you to slide around in slow corners, leading to tires destruction.
So what the engineers did was to put a third damper between the two elements activated by something like a "T" mechanism in laymen's terms. The T element allows the 3rd element to only be in play when BOTH dampers on that end are moving in the same direction (ie both in compression or both in rebound). So now you can run a 3rd spring that's stiff to control the ride height during high speed straights to prevent from bottoming, and go back to running softer corner springs to gain back the mechanical grip that you would've otherwise lost. The 3rd spring SHOULDN'T play a role in cornering because in a corner, the laden wheel is in compression while the unladen wheel is in rebound, thus the T mechanism of the 3rd spring isn't in play.
Hope that solves the confusion some people have with regards to the third spring
Edited by Cyril Ma, 28 February 2008 - 09:54 PM.