Its the tire's fault

Blue skies and a 45 degree day meant thawed ice, clear roads and a chance to ride my usual route around the campus and fair grounds for the first time since late fall. How nice it was to stop rocking in one place and bust out down the road! Right away, though, I noticed an issue with dry pavement and the WTB Stout tire that I mounted back when the snow started.

The tire has deep lugs that should be great for trails, dirt and mud, and based on this winter season I know it works well in snow, but it gives me fits on dry pavement when I'm making 90 degree turns at intersections. Now, for sure, part of the problem is that I haven't been out riding on the road much in the past two months, but still I think there is something going on with the tire.

Here's what I think is happening: The surface of the tire where the road an the lugs meet is flatter in cross section than the surface of the underlying tire. Another way to say it is that the tire carcass has a smaller radius than the radius defined by the surface of the lugs. This is fine when riding in a straight line or making very gradual turns, and it probably maximizes the bite of the lugs into soft surfaces. However, this geometry becomes a problem when making sharper turns like a right turn at an intersection where you need to stay close to the curb. The unicycle angle gets fairly acute, and the contact patch of the tire rolls up onto those outside lugs. If you lean into the turn too far you start to fall off those lugs as if falling off of a shelf, and the unicycle turns too sharply and off you go. So in a nutshell, it is fine on the straights and weaves, but unpredictable as your turns become increasingly sharp.

This symptom cropped up in the most public place possible during my Thursday ride. Riding back from the state fair grounds onto campus brought me past a popular bus stop for students making the trek from the St. Paul campus to the East or West Bank campus. It was just after noon, so the bus stop was packed, and those who had nothing else to stare at had plenty of time to watch the old guy on the unicycle ride up the hill, up to an intersection, make the right turn, and of course, flub the turn. I walked the unicycle up the sidewalk a ways, hopped back on and finished the ride just fine, making sure that at subsequent intersections I took a wide line and stayed off the shoulders of the tire.

That's my excuse anyway, and I'm sticking to it.