[SCBillandJane]

I read about Marathon tires before buying our 2003 3021KS with 15 inch tires in Feb. 2008. I live in SC, and traveled to Tampa, Fla. to pick it up. Following the advice of the forum, I decided I woudn't leave Tampa until I replaced the 6 year old tires including the spare.. Thanks for the advice. The tire store employees thought I was crazy for replacing tires that looked brand new especially the spare that had never been on the ground.
I chose Brand B for replacement tires because I hadn't read any good news about Marathons. Brand B was the only brand that this tire store had in the right size that wasn't Marathons. Not a very scientific choice. I kept the Marathon spare as a second spare since I planned a trip to Alaska. The second spare rode in the back of the the truck on a 9 week trip to Alaska. When I returned and removed the spare from the truck bed, the rubber was gummy and coming off the tire leaving my hands black. It had still never been used. I took it to the recycle center.
The Brand B tires have been from Tampa to SC to Myrtle Beach to Alaska down to Washington back to SC to Key West, Fla. and back to SC. The total milage is close to 20,000 miles in one year with no problems under a variety of conditions. When I replace the current tires, I will choose Brand B unless I can find good information that says Brand C is best.
I would have liked to have had a "scientific" or a reasonably reliable recommendation on which brand would give me the best chance not to have a blow out with all the related damage. Maybe I just got lucky with the three Brand B tires I bought. Is there such a place that has reliable information about 15 inch trailer tires?
In any case, thank you forum members for the information about tire balancing, tire age, inflation, speed, and over loading. I feel that your information saved me from an unpleasant surprise.