late response but you make a leaf sping out of 2 or more segments (1/2, 1/3 etc) and you attach them with atleast 2 axles, then you go into the script menu for the axles, then you find something called "HingeConstant", it should say "NaN", then change that to 10000, 100000 etc, that enables the axles to stretch and give you a leaf spring like system, this only works for "Legacymode = 1" axles which is default when you create an axle