So I'm confused as to the spring rates for the Tein CS. Tein's website says that front/rear is 7kgf/mm. The IS350 has a weight distribution of 52/48 so wouldnt it make more sense to have a higher spring rate in front than the back? Maybe the Tein website is wrong?

 

Weight distribution is one of many factors that goes into what a company feels are the best rates. I'm afraid that other less relevant factors such as what they have on hand, etc., are also factors that may play a bigger role in their decision. *Not trying to single out Tein or any other manufacturer, BTW*

The other factors that should be taken into consideration are the car's under/oversteer tendencies as spring rates can and do have an effect here. Some manufacturers try to get the car closer to neutral while others might try to keep the same stock characteristics. You also have the interplay between the spring rates and how soft/stiff the dampers are. Going with stiffer dampers can make up for a softer spring rate.

 

I would like the know the spring rates of the stock springs, the sport suspension springs, the Eibach, and the tein.