Originally Posted by merlinextraligh

What tends to make it a seperate category is that you can't really do it on most road racing bikes. For a gravel grinder race like Dirty Kanza, they recommend tires at least 2" wide. Doing it on 25mm tires would be insane.

Thus, there's a whole new category of gravel grinder bikes, which are pretty much cyclocross bikes with wider tire clearance.