This is the Lakeland rail trail. Google shows it starting up on a curve on M36, but slightly before 6 am, I couldn't find the trail head.
http://goo.gl/maps/LxsuTSo I knew I could probably find it in Hamburg proper, so I continued up M36 and then veered off where M36 goes north by a gas station. There, I did find it easily, and that would be my home for the next many miles.
The first bit is paved, so other than slowing for cross streets, it's hammer time. Shortly after a sweet underpass of M36 by Cap'n Frosties (even lit!), it turns to dirt, but it is pretty smooth and has fun rolling whoops.
Then at some point, and for awhile, it's crushed stone, but the top is so fine that it feels like riding in 1/4" - 1/2" of sand, killing your momentum. And whatever they mow with leaves tiny chatter bumps, so with some tenderness from Friday's antics, that was very mentally challenging.
I made it Stockbridge at the end of the trail - a marathon in less time than the world record...but not by much!
Then it started to drizzle, and even rained pretty well, then drizzle.
On my way back, I was determined to see if it did come out as Google suggested, so I took the trail past where I started on it. The pavement ends, gravel = no problem. The gravel ended...problem. It was massively bike whacking. I was on my knees for a decent portion of that. It does come out where Google says, but is unridable and wouldn't even be nice hiking. Unless it was trimmed, then it would be fantastic - the base is smooth. I wonder if it extending it is in the plans.