Different Gear Type when there's no Front Derailleur? I have a 7 speed Jamis Boss Cruiser, 7 gears in back and one up front. I've been using it fine for several months now. Lately, the chain is coming off of the single front gear, usually after stopping at an intersection when I start back up again.

I took it to a bike shop and the guy claims the front gear is not the right type of gear, its the type of gear that's meant to work with a derailleur. He says that's why the chain comes off. I'm disinclined to trust him since it's worked without problems for almost 8 months. If it was the wrong gear, I would have been having problem before now, right? Is it true that there is a type of front gear for use with derailleurs and a type of front gear meant to be used as a single front gear?
Yes, there is a difference between front chainrings for derailleur equipped bikes compared to bikes without a derailleur.

A derailleur suitable chainring is designed to assist the chain climbing onto the chainring, via ramps and pins that the chain engages into.


Non-derailleur chainrings are much simpler and are just the straight teeth.


To solve your problem, you could:


Check your chainring and potentially replace it with a single speed chainring
Get a chain keeper like this one
Or both!


More information is on these questions:


Mysterious case: chain falling off large chainring
Why does my chain keep jumping off the front chainring?