i am currently riding single speed spaced out on a 9sp shimano freehub and ride mostly in the city. i am considering getting some gears for occasional long distance ride. just wondering if this set up will work...

i have a double crank so.....single 42t chainring front on the outer with a chainguard on the inner. no front derailleur. i would line up the smallest sprocket in the rear with the 42t front to get the right chainline (maybe have to reduce from 9sp to 6 or 7 to achieve that?). and im hoping the chainguard on the inner will prevent the chain from slipping off when on the largest sprocket. also would only have one shifter for the rear der.

i know some cyclocross bikes run a chain guard on the outer, chainring on the inner, and a chain guide on the seat tube. i would NOT want to do this strictly for aesthetic reasons which are, at times, important to me. also i dont want to run a double or front der as i do not need that many gears.

i dont know much about gears so any ideas, suggestions, or faults in this set up?

Give it a try. I would set the chain line up with a 19 or 18 tooth cog around the middle of the casset and have at it. If the area where you ride if flat you will be set up. You probably don't need anything to keep the chain on the front ring. Most chains are dropped while shifting and since you will not be shifting this will probably not happen.

so are you saying i may not need a chainguard on either side or just the front?

I wouldn't expect to drop the chain ever, try it without both chaingaurds and see how it goes.

even without having a front derailleur to keep it on? i never would have thought. ill try it!