Originally Posted by
Six jours
If you cut through the casing the tire will pull apart in that spot and the reinforcement won't do any good. You're probably better off covering the outside of the casing in shoe goo or something, if you really don't have any other choice.
+1
The exposed cords are what holds the tire together. Wear through them enough to compromise their strength, and the tire will burst. The internal plastic liner might be strong enough to bridge the damaged area and buy you a bit more time than otherwise, but won't do much to stop the clock, and you can expect wear through and failure within a few miles (few meaning 10-100). For a commuter, it might be OK in a pinch, but I wouldn't leave town.
BTW- that kind of uneven wear often means the wheel is out of round. What you might do (again, in a pinch) is to rotate the worn area to a low spot on the wheel, where the wear rate might be slower. You might also try to find something to glue over the outside.