Rubber is worn out evenly across the tire tread.
Even tread wear indicates that tire pressure has been maintained at the correct inflation level during service.
Tire should be removed at the following condition whichever comes first across the tread;
If it is necessary to continue the tire in service beyond the limit i), the tire should be removed either at the next maintenance base or the limit ii) happens, whichever occurs first.
Specific removal criteria shall be defined by instruction of airframe manufacturers, such as AMM. Such document takes precedence over this manual.