Originally Posted by Blip Bavarian
none of those apply
Take another look!
These tires are Michelin Pilot Sports (the original ones, "PS1's") and have a straight center tread block which, mysteriously, is not in the pictures (passenger side more so than driver's). On the worn tire you see no center tread and some outer tread. The attached pic shows what these tires look like originally. Pretty good argument for overinflation...
Kingleh has a VERY good point - pressure gauges are notoriously off (sensitive needles, prone to drops, etc), and especially the cheap ones. Invest in a good gauge, take care of it, and check it against others. Forget those pen-like/pop-out things and I would even avoid most at places like Pep Boys. You can pick up an Intercomp or Longacre for as little as $30 or so and you'll want to use it all of the time!