I have grooved a set of 36" SX Swampers that had the center lugs worn down to were it was smooth all the way around.I grooved it back out to were it looked like it did before it was worn & then ran them until they were completly bald.most of the ware came from road miles.Those were some tough tires,they never needed a plug & never leaked. Go for it ,you will get another half alife out of them.