There's no reason the PS9's would inherently "bob up and down" or rattle your fillings. That's the beauty of coil-overs, you have a huge selection of spring rates to choose from, to deliver the ride/performance you desire. You could fit springs softer than stock, or as stiff as a rock. Do a search on PS9's, I think Insite had lots of information on spring rates in his thread. There is no ONE optimum solution, everything is a compromise, and heavily dependant on your personal desires and vehicle usage.
Correction: insite's thread was on KS coilovers, but the spring rate information should still be valid.
KSport Coilovers: All About 'Em
Threaded Mode
