i suspect this is under inflated because;
when the air pressure is not enough ,weight from the car will cause the wall of the tire to scrub on the road...judging from your pic the scrubbing appears on the mid wall of the tire and traveling for a long distance will wear it thin both inner and outer wall.When it reaches the point of breaking,the tire will come out...Please check the tire pressure constantly and never leave it under inflated...
when the air pressure is not enough ,weight from the car will cause the wall of the tire to scrub on the road...judging from your pic the scrubbing appears on the mid wall of the tire and traveling for a long distance will wear it thin both inner and outer wall.When it reaches the point of breaking,the tire will come out...Please check the tire pressure constantly and never leave it under inflated...