35mph for a short spell but my vision went a bit funny with the effort, won't be trying that again for a while. That was doing about 125 RPM in a 95 inch gear. I didn't know the speed until I stopped to check, no way could I have seen the computer on the move at that point. 125 RPM isn't that big a spin, I can do that on lower gears, it's the combination of spin rate, larger gear and lack of strength. Stronger riders wouldn't have the latter weakness.