bias ply tires

I would run the bias until they needed replacement. Then I would look at all manufacturers and make an educated decision as to tires. There are other brands out there that have been very reliable such as the Carlisle RH.

More Info-
http://www.tirereview.com/article/88909/carlisle_has_new_trailer_radial.aspx
and here
http://finance.yahoo.com/news/Carlisle-Radial-Trail-RH-iw-2753166234.html