Originally Posted by sykerocker
If you're rear derailleur is adjusted correctly, the bike will definitely look better. If it's not adjusted correctly, the chain can lodge behind the freewheel and lock up the rear wheel. Which means you're going down. Hard. An excellent way to break a wrist - like I did four weeks ago.
Oh crap! And I thought I was one of the cool kids because I took the guard off! Well, kids, as Officer Friendly says, "Safety is Cool!" Guess you gotta trust that advice.
Or wait--I live in a relatively flat state, so I never go down that far on the freewheel anyway. And if I do, I'll be chugging uphill very slowly. Think its still necessary?
Oh, and on the freewheel--you asked about gear ratios and stuff. Most standard freewheels are something like 14-24, meaning the smallest cog is 14 and the biggest is 24. That's probably good enough for most road bikes. But there are freewheels out there that have even smaller cogs for super high speed. I also have a 14-34, where the first 5 gears are "normal" and the 6th, largest gear, is a huge step up. This would be good for a touring bike or if you live somewhere where there's a lot of hills. Point is you can't really mess it up, and you'll be fine going with what you can find (freewheels are relatively obsolete, so LBS/REI are not likely to have a wide selection).