Well, country roads in AR. They don't really seem dirty to me, but they're all I'm used to. I do end up on a dirt road sometimes, but not often. I live in Fayetteville which isn't really a big, dirty city. I've only cleaned them once, but I've only had the bike since last November. I may just be a clean freak. I plan on cleaning them again soon. I guess they're working well, so I'll probably just keep them until they need replaced.