I built a 35mph capable ebike from a lot on a MTB with dual disc brakes and the best s-pedelec tires I could find and I'm pretty stressed out already at 35kph.

I built a 35mph capable ebike from a lot on a MTB with dual disc brakes and the best s-pedelec tires I could find and I'm pretty stressed out already at 35kph. I can't imagine doing 50kph much less on a bike that isn't intended for it. You really would have to be almost suicidal. I have to say though being able to keep up with cars when I can't have a bike lane is pretty nice.