I tend to agree with elyhim. But living in IL, I can ride a class 3 with no issues. What concerns me about all the speed hacks, does the rest of your bike support the speed? Large rotors, hydraulic brakes, heavy duty suspension forks, high quality tires, etc. I've reached 41.8mph on my Haibike XDURO Full Seven on steep grade. Of course when I hit the bump at the bottom, the thought crossed my mind about exceeding design limits. I know my helmet would do nothing if my head hit the pavement at that speed either.