Pedaling folding bikes

[Will]

I was browsing around considering my next e-bike. The Dahon folding bikes look promising yet, is their gearing tall enough to pedal 20 mph, let's say at a cadence of 80? They state gearing is 92", (occassionally higher for pricyer 8/9 speeds). If that means 92" per rotation of the crank, then 92" x 80rpms x 60min /by 12" = 36,000 /by 5,200' = about 7mph. For a bike to cruise 7mph doesn't make sense to me. What am I miscalculating? And, What is a realistic top touring speed for a Dahon folding bike?

 

[Miles]

It's not based on the development (as the metric system is), it means the equivalent of having a 92" diameter wheel geared 1:1

You can use this calculator to work it all out:
http://www.sheldonbrown.com/gears/

 

[Will]

Ahh, another great Sheldon Brown site, God rest his soul. Thanks Miles. It's 22-23mph @ 80rpm, perfect!

 

[JinbaIttai]

How easy are those things to ride?
I want to make an ebike for my girlfriend next year and I'm looking for something easier to ride than my bike. She tried it and couldn't really ride it.

 

[Will]

While on the subject, not only how easy, but also how rugged? They probably don't fare well at 30+mph, yet how about 15 to 22mph? Will those little 20" wheels soak up the rough stuff along the road's edge?

 

[Miles]

Speed and small wheels isn't really a problem (although the change in aspect ratio of the contact patch does have an effect). 20" wheels are much stronger than larger wheels. I'd recommend suspension, though. Even one of the Pantour suspension hubs will make a 20" wheel more comfortable than the equivalent 26" wheel.