You shouldn't have any problem digging any soil with that chain. The only thing you might notice is that chain in softer soil won't clean the bottom of the trench as well. Normally that isn't that critical. Most of the time you can dig a little deeper to compensate for the spoils left in the trench. I took care of a fleet of machines including 25+ "pedestrian" trenchers for 8 years. We ran "combo" chains, half shark teeth, half cup teeth. It was a good compromise, we got the carbide teeth for the hard soil, and the cup teeth for good clean out. All of our tire machines were set for 6" width and the track machines were set for 8" width.
Brian