yeah the higher the spring rate the harder/stiffer the springs will be. You really need to ride in a car with the coilovers to tell how much stiffer the ride feels. My tein ss feels close to stock, and i use it as a daily. None of my occupants, gf, parents, bro really noticed a deterioration to ride comfort compared to stock. I know members with buddyclub N+ which is similar to tein flex in spring rates, and they find it comfortable.
If you're after a slammed look, tein flex or N+ are what i would go for. If mild-medium drop and want close to stock spring rates, SS for price and tein CS if you want better quality.
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