I've been touring on a Bridgestone MB-1 for over 10 years. I've left the original rings which do "max out" on many downhills. I figure why not coast? I don't think over the course of a long day getting any extra spin out of my drivetrain on 6%+ downhill is going to get me to my destination any more than a minute or two sooner. I put aero bars on my mt. flat bars and in an aero position I've hit 50+ mph on the bike fully loaded with front and rear panniers. Even with a 53/12 I would have maxed out at that speed.