Bicycle Mechanics - Know of any light chain guides

I only use the big chain ring on the front so I went without a front derailleur for a bit. Then I noticed the chain would fall out (to the pedal side) if I hit a bump or shifted a couple of gears. It seems that the front derailleur also helps in guiding the chain on the ring when not shifting. So it seems I need some sort of light chain guide as I would rather not keep the derailleur there. Does anyone have any recommendations?

Adam

A front derailleur works wonders. Running a geared bike without a FD is asking for it.

I have an electric assist motor. Even on steep hills, I don't need to gear down the front gears.

Adamtki:
I'd love to see your setup - not that I would ever put an electric assist motor on my bike, but, I sure would be curious to see how yours is setup.

As to your question, what would be so terrible about placing a FD on the bike even if you choose not to attach a cable to it? Position it where it can serve as a guide to keep your chain from jumping off. As they say in the infomercial, "set it and forget it."

It would seem to be a quick, simple solution to your problem using materials already in existence designed for the (well almost the) purpose.

Tell us more about your assist motor. How do you power it? How do you replenish that power?

I admit you have raised my curiosity.

Caruso

I only use the big chain ring on the front so I went without a front derailleur for a bit. Then I noticed the chain would fall out (to the pedal side) if I hit a bump or shifted a couple of gears. It seems that the front derailleur also helps in guiding the chain on the ring when not shifting. So it seems I need some sort of light chain guide as I would rather not keep the derailleur there. Does anyone have any recommendations?

Simplest is to use a front derailleur stuck in one postion with the adjustment screws.

You can remove the extra chainring to eliminate the extra weight. Kind of sounds like you're heading in a singlespeed direction...

For the electric assist, I use Bionx (http://www.bionx.ca). The battery is mounted on the down tube. It's installed on a steel frame Trek 720 (hybrid). I use 700x28c wheels. The electric assist helps me cruise about 4-5 mph faster on flat terrain.

Yeah, I can keep the FD there. Just thought I could find something lighter.

peripatetic, know of any light 53t single speed crankset?

The FD doesn't weigh very much. You could get some carbon chain guides like the cross racers use when runnning a single chainring setup. But why worry about a few grams when your using an electric assist and battery?

if you switch out the chainring on there now for one designed for fixed gear/single speed then it should stay on there better without a FD. Multi speed chainrings are ramped to make shifting easier, and also have shorter teeth than a ring designed for only SS.

if you switch out the chainring on there now for one designed for fixed gear/single speed then it should stay on there better without a FD. Multi speed chainrings are ramped to make shifting easier, and also have shorter teeth than a ring designed for only SS.

Thanks. I didn't realize that. That's good to know. Do you have any single speed recommendation? I'm looking for 49-53t.

My goal is to make the lightest electric bike possible (without spending a ton of money), by the way.

Nothing in particular, but harris cyclery has a good selection sorted by BCD. I'd give you a direct link but I can't get their page to load atm for some reason.