I have hit 46.3 MPH on South Park Drive at Tilden Park (Berkeley, CA). I did this on my old ass Schwinn MTB from 96' or so. Since joining the cycling team here, my addiction to biking has yet again become a bad habit. But hopefully I'll be getting a new ride soon and looking out to break that record and do bigger drops. I'll admit it is pretty scary going 40+ MPH if you keep looking at your speedometer. Sometimes I won't even notice I am going that fast until the ride is over and I look at my max speed. I hit 39 MPH during a collegiate race this season and did not think I had even reached speeds like that during the race. The best thing I find to do is ride the hill several times to learn the best line and then bomb down it. Doing it on a low traffic day is key so you can take turns wide without worrying about becoming windshield splatter.