Haven't managed to dynamically break anything yet, but I'm sure my day is coming. Hopefully after my shiny new helmet arrives. <G> Just a basic 7 gear cassette on the back and a single 42 tooth sprocket on the crank. Don't quote me on how it's SUPPOSED to work (I do plan to read the book eventually) but ... the motor is built right into the rear hub and drives the axle directly. You can free wheel with the pedals or just keep them stationary when the power assist is on, but I prefer to run through the gears to help the motor and get some exercise while I'm at it. That works well up to around 10mph - anything more and the 7 speed cassette can't really keep up. From there, just sit back and hang on! I've had it up to around 20mph just fer shitzengiggles, but truth be told, I ain't really in that much of a hurry anyway.