If you feel that you might have hydroplaning issues with your current worn tires then its time to change. The money you will save over the next few thousand miles is nothing compared to the risk to your car and your health if you get in an accident because of a spin in the wet. New tires are cheap insurance. Really, only you can decide when its right to change.
I usually go past the wear bars some, but change them before any cords or belts are exposed. I don't drive the boxster in the rain much so hydroplaning isn't an issue.
Hybrid Mode
