I don't measure roads in MPH so much as comfort. Chip seal vibration hurts my neck almost as much as brick. I wouldn't ride it at all without my bike's suspension fork and running the tire pressure a bit low. My neck and shoulder are still aching from riding the rural chip seal route twice this week. For some reason it feels more unpleasant than gravel. Gravel feels good, like a vibrating massage chair. Not chip seal.