opaul, can't answer for others but I put as much tension as my spring allows. However I don't think it is tension that causes one to break. It is a flaw in a new belt and a compromised area in an older belt. I guarantee when I hear any change I start to back off and I hit the kill switch from the side instead while I am standing behind the grinder. Like Bladegrinder I have almost always heard a change. The one new one that blew was only on the machine for about a minute. I guarantee when one blows, she will get your attention! Oh and the new one the belt that blew, I could never visibly see what caused it too fail!!