I'm just a guy with a bicycle, but why tires like 700x38C isn't recommend?
I needed new rear tires for my bicycle, so I just took the numbers from my existing tire.
At the bike store the guy was like "38? It is like this wide" *shows around the same size with his hands*. I was like yeah, it is probably in mm.
I had to show a picture of my existing tire to stop pestering me, but he even had it in stock.
I don't want thiner tires, roads are trash, if there are roads at all, and I only have a small front suspension. Even these tires cut into gravel (I rarely bike there). I don't think I can go wider or it wouldn't fit under the fender.