Dave, I was out puddering around in my garage this weekend and remember this post. So I put the 34 in the driveway, got out my trust retractable metal tape, and measured the clearance between the macadam and the bottom edge of my front valance.

Three and one quarter inches (3 1/4") ! Gotcha' by one half inch! I have yet to hit anything that I wasn't aiming for. I suppose that if both tires when flat exactly at the same time I could have a problem. Especially if I was on the PA Turnpike.