Quote:
Originally Posted by M3SQRD
Is the rear a divorced spring or coilover spring? F/R 100/120 N/mm (571/685 lbf/in), if this is a rear divorced spring, then that’s an atypical spring setup for the f8x. The front motion ratio (MR) is ~0.97 and rear MR is ~0.62. Wheel rate is: WR = spring rate * MR^2 so your WRs are F/R 537/262 lbf/in. Ratio is 2.05 - biased with too much front rate = understeer/slow to change direction with steering input. As an example, the f82 GTS has F/R 400/700 lbf/in with a WR F/R ratio of 1.40 on BMW-tuned KW 3-way Clubsport dampers. Ratios >> 1.40 results in severe understeer. Even for a primarily driven street car, the rear rate is low. I’d recommend playing around with rear spring rates because there’s a lot more to extract from the car with little impact on road ride quality. On my wife’s m240ix, I have a set of MCS 2WR with F/R 500/800 lbf/in (divorced rear) + remote reservoir pressure of 100 psi and it’s one of the best street setups with excellent ride quality yet improved performance at the same time with just a few changes to R and C damper settings.
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I think I'm going to try to move the 120 to my front and purchase a set of 160 for the rear.