I've run Conti GP3000 23s over dirt, gravel, and really rough roads with only two flats in the life of the tire - 1 goathead and 1 pinch flat. That said, my primary 20 mile route to work invoves some really rough roads so I'm running them in 25s now. I like the extra volume and really don't notice the rolling resistance. I hear that the GP4000 roll even better.