I have one long downhill that is avg 5-6% grade... (some section 10%) for 3.5 miles. If I just idle, it tops out around 32mph. Typically doing light pedaling to keep my leg warm and hitting around 35-38mph. (Yes, that speed is much easier than climbing same thing back up at 7mph+) Fortunately this hill is on the way to work so I don't really sweat much on the way. (getting road bike soon and wondering how much faster downhill would be...) Oh... btw, this is on folding bike... Dahon Speed Tr...