Just for clarity of the situation --- those tires have MANY MANY long distance trips -- as in Scottsdale and back to Seattle several times -- LA and back several times - So it isn't the air pressure that "suddenly" blew the tread off TWO tires on the same trip.... my guess it DELAMINATING.... since both tires suffered the exact "tread loss"....Neither tire blew out the sidewall....
Just FYI -- Load range "E" tires are 80# cold max pressure --- you can have the same size tire with a lower load range rating and it will have a lower max pressure.
