Originally Posted by howsteepisit
So as a question for you all, how slow can you go until you start weaving and loose balance? I can only drop to about 4 mph or so. Also, back in the day (Old Fart story coming up), when I was actually in good shap and worked in a bike shop, I toured witha low gear of 40 x 32 (47 inches) and thought it was more than low enough. So thats the kind of advise I tended to give folks in the shop. I was wrong! Now much older, fatter and less fit, I find that I need to go a low as I can and still stay upright on the bike. Remember those kids in the shops tend to be very fit highly enthusiastic cyclists. As such they have no clue about what the restof us can do or want to do with comfort.
That's the main reason I've never listened to the snot nosed kid behind the repair counter at a bike shop - even when I was a snot nosed kid
Most of them are clueless and think that everyone should be able to turn over a 42/20 gear for a low gear and if they can't then they aren't really cyclists anyway!
Babysaph, the lowest gear combination you can possibly go is a 20 tooth crank wheel (front) and a 34 tooth cassette gear (back). You really do need to get your hands dirty and count the teeth you already have. Bikes come with different gears and we can't tell you what to get if we don't know what you have.
If you look closely and you can see numbers on the cassette gears (back). They are going to be near the outer part of the gear and will have a couple of letters and a number. The outer most gear will probably have a number like 12 or 11. Once you find the number, you should be able to find it in a similar spot for each of the cogs (gears). But these numbers might be obscured if your drivetrain is dirty. You can also count the number of teeth on each cog (for all 8 cogs on the cassette). Since you are only interested in the low gear, you could just count that one (the largest cog on the rear cassette). My guess is that it will be either a 28 tooth, 30 tooth, 32 tooth or 34 tooth cog. If it is a 34 (my best guess is that it is) you can't get a lower gear in the back than that. Any of the others you can change but you will probably have to get a whole cassette to do so.
Now for the front, look at the gears on the front, they should also have a number on them (look on both sides of each gear). If they don't you can count each tooth on each gear. Or, since you only want a lower gear, count the ones on the inner gear (smallest). I suspect that the number you come up with will be either 28 teeth or 22 teeth. You can go lower than this. The smallest you should be able to find is a 20 tooth gear.
After you have the numbers go to a bike shop - buy the stuff from the bike shop and not on-line since they have to pay the bills and advice isn't usually free - and ask them about the parts you need. If the snot nosed kid behind the counter says it can't be done, find another bike shop or find an older mechanic
It's a fairly easy replacement for both the cassette and crank (if the gears on the crank can be replaced. Some can't).
If you want to read more about cassettes and gearing go to Sheldon Brown. Cassettes are
here and how to figure out your gears is
here. While you are there take a look at how all this stuff works together
here.