What are the drawbacks of a single gear bike?

There are pros and cons to a single gear bike.

The pros are its a more direct power delivery method to your drivetrain and also simpler / easier to service.

The cons are mostly on the terrain (hills vs. flat) that you're most likely riding day-to-day. Multiple gears do allow a more dynamic ratio range of power delivery. That being said, we believe we've selected a good gear ratio and technologically (through to make as many customers happy. You can have a professional bike mechanic adjust the size of the gears, which won't disrupt the Vela's motor assist.