The only reason I went with 50mm tires on my "Frankenbike" is that streets & sidewalks here resemble the craters of the moon. I have more than one friend who has endoed when their 25mm tires got buried in a crack of the road. I rode recently with friends who both run 37mm tires on their commuter bikes. I brought up the rear on my Townie with the 50mm tires. They ducked & dodged frequently, occasionally having to brake hard to avoid obstacles - I just rode over the potholes & kept on going. My Kona came with knobbies, but it rode too rough. The Continental "Retro Ride" tires seem smoother & more comfortable.