The Goodyear Marathon is going the same way as the do-do bird.
In its place is the Goodyear Endurance 20575R15 load range D (8 Ply)
Product # 724861519.
A new tread design help tire to remain cool while towing heavy loads.
A big improvement over the old Marathon with beefier sidewall construction.
Better inner liners minimizes air loss in trailer applications because of 100% halobutyl rubber.
Hope this helps