With pedal assist at 2, this setup ranges 20-30mph with essentially no effort, just moving my feet in a circle. The battery is rated at 13.5ah. I was hoping for 30 mile range. If you're getting 40 on yours I should be in good shape.
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In a practical sense, 25mph is a much more reasonable speed for a bike. Above that doesn't leave you much room to correct for mistakes. It's fun to go full speed, but there aren't many places I'll be able to do that. That said, it's just a mile from the house downhill into town to a coffee shop and a brewery. The extra speed does keep me moving as fast as traffic on the road, which feels safer than getting passed.
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And thanks for answering questions about your build. Very helpful.