I recently replaced one rear tire (265/40ZR18/RF N3).  I measured the tread to see what the difference between the two rear tires was.
The PS2 has three grooves.  I measured 8/32 in the center and outside and 7/32 in the inside groove.  According to Michelin, on a new tire, the three grooves should all be 10/32 deep.  So I was starting to get pissed, thinking I bought a used tire 
 
 
For sanity, I decided to measure the tires on a new car at the dealer and it measured 8,8 & 7, not the 10/32 that Michelin says.
So what going on?  Does a 10/32 tire come with only 8/32 of tread?