I did a 35 mile jaunt yesterday on my Marin. I've got the factory "dirt/street" Kenda, Krossplus 26"x 1.95" tires on it. I was a little heavier laden with gear than usual, and I noticed that coming down long hills once I got beyond about 25 MPH I started feeling an intense wobble, almost like the whole rear wheel was coming off. I stopped, checked it and everything was kosher. Nothing loose at all. Then I'd start again and get this death wobble. I did some experiments and noticed it only happens when I'm coming down the side of the road on light road sand and gravel. On good solid pavement I feel no wobble even at high speeds.
Given that roadside sand and gravel is ubiquitous in Alaska, I'm wondering if I should be eyeing a different tire. Speed is not important, but I don't want to wipe out! I've never been a fan of the dirt/street concept and actually don't mind light knobbies for what I do.