Make sure they are properly inflated.  Under inflation is a major cause of trailer tire blowouts.  My Goodyear marathons are checked frequently and are at 44 psi.

The one tire I had to replace was $105.00. That includes balancing and all that at Les-Schwab. I just put it back on the spare tire rack but I would hate to have that happen and not have a spare.

The tire that blew was not bad? I must have hit something to cause it to blow out like that. Headed to California in a little over a month. Would not even think of going without a spare tire.

I swap mine out when one of them "blows". Like last summer on the way to Oregon for Labor Day.   
Ray

Take them to silver lake and run them off the edge of the ramp, then theres no question what you need to do.      I'd replace them !!  Look at Mike's post, his tires can't be more than 2-3 yrs old.

Maybe I should have read this post before last Friday. I just blew one out on my way back from Lake Washington Friday afternoon. It was neat!

Hi Glen -
Before dropping five bills for new tires, I might suggest that you check the wear in the tread.  Is it even or are there wear spots in certain areas, any flat spots or bulges.  Sidewalls are really the location of the weaking elements of time.  Are they checkered near the bead of the rim and moving out to the tread?  Some tires can last a very long time.  Just my two cents.