Telling how much tread is left - Drag Radials

In a measurement in 0/32 of a inch,what is the depth of the thread lines in the radial?They normally come with a new depth of 7-8/32,what is it now,or are the tires lost all thier rubber.I would check out the BFG web site for a spec and post it to determine if they are good or no good,Mrmopartech