Originally Posted by swamp2
Where is the test that shaves a tire so much that there is not enough tread life left to even finish the session? I don't think that test ends up getting run very often and if so only by a big accident.
Depends on what the test entails. You don't need a track session to test a tire's lateral grip on a skidpad or CoF. The Skip Barber people could have easily tested a tire they shaved to almost no tread in a relatively controlled environment (not necessarily on a car), and I don't see why that would be an accident. If you reread the quote from that book, you'll see that they are stating, in two consequent sentences, street tires are run from 5/32" down to bald and that there is no significant reduction in CF from 5/32" down based on their testing, so to me, that suggests a range for their testing and bald means almost no tread.
Regardless, that specific scenario is not relevant to this thread to begin with since, as far as I can tell, nobody here has referenced starting a track session or a race with tires that were about to cord. And, in the interest of safety, I hope nobody has plans to do so.