Mark from Saint Louis, MO 63144 on 2/20/2025 7:06:21 PM:
The trail surface is packed crushed limestone and gravel. You might find a few paved sections in towns like Hill City, but for the most part the trail surface is limestone and gravel.
I guess you could ride parts of the trail on a road bike, but I certainly wouldn't try it for most of the trail. I road it on a Trek Checkpoint with 40c tires and I really appreciated that tire width on most of the trail. There are some really loose sections on the trail that thin tires would dig into, I think. 25c or 28c wouldn't be something I'd recommend.
The last time I was on the trail I saw many E-bikes with up to 50c tires. In my opinion, 35c width is the smallest I'd go with.
Of course, I'm sure many have ridden the entire trail on a road bike with narrow tires. I just don't think that's ideal.
Watch out for the E-bikes. They are becoming prevalent on the trail. They go a lot faster than they should IMO and the trail stewards really don't do anything about it.
Good luck and enjoy the ride.