There's no such thing as a dumb question, but there most definitely can be dumb answers
Many places that sell re-treads will tell you that they're safe and that it is common practice, they'll even site trucks, buses and airplanes as an example. However there is one really BIG difference: truck, bus and airplane tyres were
designed to be re-treaded passenger car tyres were not!
To over-simplify the process, they take a worn car tyre, remove any remaining tread and then stick on a new one. These new treads are often refered to as "gator backs" (for obvious reasons). The big issue is that the binding of the new gator back to the old tyre will
never be as good as the original constructed tyre and the tyre may also have other issues which are not visible to the eye. As a tyre is used not only does the tread wear but the overall structure of the tyre becomes weaker, more rigid and more fragile.
I could be wrong, but I'm fairly certain that most insurance companies won't cover you if you have re-treads.
The speed limit of a re-tread tyre is greatly reduced to that of a normal tyre, so to is its strength.
my personal opinion: retread = death wish