"Typically" this failure was caused by running the other tire flat. Okay he says that the inner went down when the outer separated but most cracked rims I saw where from flats, loose nuts or overloaded. (I put 40 years in wrenching on and off road equipment)
I realize that these are not aluminum rims but Alcoa has an excellent website with rim maintenance discussed in
http://www.alcoa.com/alcoawheels/cat...al-English.pdf