get new tires
your on the highway pulling a trailer I assume,
heat, max out tire pressure, extra weight on vehicle, all signs for a blow out on old or defective tires.
you want the best tires you can afford, in the best condition.
I have also had the tire valve stems go bad on me before the tires when bad. take your tire valve stems and bend them back and forth, gently, if not metal stems, see if you find any signs of cracking on the valve stem.
if you have a 2500+ size truck, then be sure to buy top quality metal valve stems.
sidewall cracking, that is always what got me first on mich tires, great tires but the sidewall would show cracks, did not give me that warm fuzzy feeling,
the new set of mich I have on my 2500 dodge drive great, company rep said they had that sidewall cracking problem solved. we will see in the next couple of years.
always lean to the safe side on tires and maintenance !!!!!!