How far can you run a pair of M/T ET street radials down to?

["Turbo-T"]

I have a pair of well used M/T ET street radials that have 17 or so passes on them. The wear bars are flush with the rest of the tread and the centers are pretty much bald....wondering how much longer I can safely run them before they become too worn to drive on/run the risk of blowing?

Thanks in advance

 

[2QUICK2B6]

i usta change oil an tires at same time 2,500 miles they will still work when u cant see anylines ... then its time to change ??????????? 17 passes ? I do john force burnouts an can get atleast 80 passes