In my experience, both can be detected and removed from the outside before the bead is even unseated. On just one occasion, I did a full examination of the tire through two revolutions before I finally found the wire from a steel-belted tire, which was folded over into into a groove in the tread, making it almost hidden. Once the bead is unseated and the tube pulled out, it is easy to reach in and feel for anything projecting through the tire.