Thanks all - all great suggestion.

I am EXTREMELY careful in mounting tires and tubes and rarely uses a lever unless I absolutely have too. For example, if its cold and not as much give in the tire.

I like the idea of heat or wheel issues but I have double checked the wheel and both blowouts were on long stretches of flat road with little braking action.

I think for this one the more obvious answer is a flaw in this particular brand of tire. If i weighed 180lbs, perhaps the issue would never arise but being in the 280lbs I think Im really putting the tire thru its paces

Much research has revealed MANY decades long cyclists who have had issues with these tires blowing out. Cyclists who have not had blowouts in 25 yrs of cycling have had them when running these tires.

My new Nashbar tires shipped today so Im hoping thats the end of my blowouts.