Just an aside but we don't really have many actual gravel roads in California. I'm sure there's some somewhere, but they aren't common. I remember seeing more when I was a kid. Dirt roads are typically dirt. Usually it's got enough clay in it to stay together, but they can get pretty sandy in summertime. Occasionally I'll come across fire and access roads that are spread with railroad 'gravel', which is more like sharp walnut sized rocks. Those roads sure are a joy...
I remember a lot of those sort of in between roads where they spray down some tar, and spread gravel across it. I forget what they're called. Haven't seen one in a long time.
Therefore, I don't have any gravel bikes.