Originally Posted by
chasm54
If you're carrying a spare anyway, ...... Ride until the rear needs replacing, then switch front to rear and put the new one on the front. Always a good idea to have your newest tyre up front.
+1, If tires are available en route, either as a carried spare or bought, then when the rear is shot, toss it and replace. I don't bother rotating, and would probably just put the new on in the back, but it's OK to rotate the front tire back if you prefer. OTOH - (IMO) it's not OK to move a rear tire up because of it's wear pattern.