I'm running 17 inches right now for the winter on continental vikingcontact 7. Its inflated to it's near minimum psi rating. The ride is still very harsh when going over small road imperfections. My mercedes GLK has upgraded bilstein suspension and it's still not as stiff as the cx-9. There must be a way to make the ride softer without having to change the tires. Nobody makes softer struts and springs?