Glad you revived this thread. So much has changed since it was started. I had proposed that a great place to start would be Midland, for the Pere Marquette Rail Trail starts there. Well, it just got flooded out. It was so incredibly sad to see the bicycle tridge underwater. Made international news.
I know the NCRT as well as anyone. Started in Gaylord for my very first tour. The gravel is hard pack, so it's pretty fast. I think 28mm or greater should be fine. Also, it's my understanding that the extension from Gaylord to Waters is ready, which makes the trail almost 80 miles. Finally, Waters is the highest point in the Lower Peninsula so it's downhill most of the way, although at a slight grade.
EDIT: I just realized you wondered about the ECRT I believe, which goes to Alpena, rather than Gaylord. I've ridden that one too. The two trails join in Cheboygen for the final leg to Mackinac City. It also could be ridden in 28s or above. Minimum tread. The trail is somewhat rougher than its neighbor. Not as packed. The only parts to watch out for are intersections. They tend to be sandy. A gravel bike is the perfect setup. A mountain bike would be overkill.
Last edited by Lanesplitter; 05-23-20 at 06:15 PM.