Originally Posted by Colnago Mixte

Assuming you're a guy, I think underwear (if any) should be the main concern. If they're loose boxers, everything is gonna be bouncing and flopping around under there, and hanging over one side of the seat then the other, then getting jarred around with every bump in the road.

You want something that's tight fitting like cycling shorts, and doesn't have a thick seam that passes between your sit bones and the seat like regular y-fronts do. Boxer briefs I find ideal, but they need to be tight enough to hold everything in place, or they're no better than regular boxers.

I have been doing most of my riding in regular shorts this summer, and I was shocked to discover I'm now "growing" my own chamois on my butt. Sit bones are now almost as tough as the bottoms of my feet. Rare antelope goats all over Europe are celebrating the news that now one less animal will need to die to provide my butt padding. And the best thing is, modern butt callous technology is SUSTAINABLE.