i bought an aftermarket one used off someone, and was wondering if the was some kind of formula used to set it ... it twists on the top and says harder --> and softer <-- i am running stock psi on a s4. thanks

looks alot like this one.. but not the same..

 

The harder/softer probably has more to do with the sound then anything else.

 

cool .. i hope thats it. i would hate to be driving around with it set to 15psi when im only at 7psi!

 

haha that wouldn hurt ur car, like he said, the harder and softer is mainly for sound, as long as it doesnt leak at idle.