Originally Posted by aus
Could someone explain what the helper spring does? I thought it was to keep the main spring lightly compressed in case you got a wheel off the ground? But it sounds like it takes part in the total spring rate in JAJ's discussion.
I also know Orb had some issues with the KW kit, but he did some modification's to his kit.
A helper spring is a gap-filler. They're usually wound from ribbon instead of round stock. They're deliberately easy to collapse and have a low collapsed height. When extended, they keep the main spring in place so it doesn't slop around while the car is in the air on jacks or a lift. Once the car is on the ground, they're fully collapsed into short cylinders. They don't contribute to the "springiness" of the suspension.
From my read of ORB's report on his 335i, he modeled the suspension and computed the spring stacks that would give him the performance he wanted. He chose Swift springs with "longer-than-normal" travel and had some special mounts made to allow him to achieve both the desired suspension travel and resonant frequency that he wanted for his car. He very kindly gave me some spring recommendations that I may well implement after I've had a chance to shake down the out-of-the-box KW setup on the track.