Polaris 2001 High-Performance Snowmobile Service Manual (PN 9916690), Page 267Get this manual
STEERINGFRONT SUSPENSION Dual Rate Springs
During initial compression of dual rate springs (two separate springs stacked on top of each other, both springs will compress resulting in an initial spring rate that is combination of both springs, yet less than either of the individual springsThe chart at right shows the inital combined spring rate using two individual spring ratesThe inital spring rate is based on the formual belowFor example, if you stack 150 lbinspring in combination with 225 lbinspring, the chart will give you an initial spring rate of 90 lbinAs the springs compress, there is point where the small spring compresses to solid, or the spring retainer contacts the transition spacersThis point is called the transition pointAny compression of the springs after this point is reached will result in spring rate equal to the spring rate of the long springThis is true because the smaller spring is no longer being compressedInitial Rate=(Spring Rate #1) (Spring Rate #2) (Spring Rate #1)(Spring Rate #2) Example: (150 lbin) (225 lbin)= (150 lbin)(225 lbin) 33750=90 lbininital spring rate 375