I've got a tire with a good amount of tread left, but there's a cut from glass that goes through. It's pretty small, a few mm. However, I've now had two leaks because stuff seems to be getting through the cut to the tube I guess. Anyone ever plugged a cut with shoe-goo? Or is there something else I can use as a permanent repair so I don't have to buy a new tire yet? Seems a shame to retire a tire that is otherwise in very good shape. Thanks....