I bought my Cro-Mo steel mountain bike when I was stationed at the Pentagon. Not a lot of off-road riding in NOVA or DC so the first thing I did (right after the test ride, but before I took it home) was replace the knobby tires with 2” slicks. The knobs were awful on cobblestone streets, but 2” slicks could handle the streets & potholes, bike paths and occassionally grass lawns with ease.
The three tires I’m looking at now are the
Serfas Drifter City Tire - 26 x 2.0,
Continental Town and Country Tire - 26 x 2.1 and
Electra Townie Original Bike Tire - 26 x 2.0. On all three the center line of the tire is smooth and if on pavement that’s your point of contact. Move to gravel, grass or dirt and the not so smooth areas of the tire make contact.