Quote:
Originally Posted by Westen86
Springs are measured in lbs/in or kg/mm. If you lower a car, it gives the wheel less space to travel. So you need a stiffer spring to stop the suspension from bottoming out. Thats the main reason for coilovers to increase spring rates so much.
Extreme lowering coilovers designed to drop a car around 3-4 inches will have rates in the 12-20kg/mm range. No suspension travel means a really hard spring. On the other end of the spectrum is the (*in development) 949 Racing coilovers. Designed to run only about 1in lower than stock and managing to keep a 175/150 lbs/in spring. Or about 3.1/2.7 kg/mm respectively. These coilovers are made to run over apex curbs without upsetting the car in the middle of a corner. These are also capable of handling a 200tw tire. Dont ask, I dont understand how they do it either.
If youre not running any serious downforce, 6/6 kg/mm seems to be the most popular. A few are 7/6, maybe 5/6. What you decide will depend on tire size and grip. Stickier tires on a racetrack will lean toward stiffer in the front, while street tires doing autocross will want a soft front end.
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So given that a particular damper is manufactured to match the spring rate, then theoretically the spring rate could be irrelevant? After lowering I am seeking to keep the handling as close to stock as possible. Without getting to scientific it looks like I should start with a stiffer rear than front, according to the stock fr-s numbers.
I'm very hesitant to go too stiff because of a thread that Dadhawk posted here. I can't find it but he mentioned that the platform requires lots of suspension travel and that lowering will reduce the already narrow travel range. I'm not sure if that was in reference to dampers/springs as a whole though.