The current trend in bicycle drivetrains is 1x11, with one chainring in front and a wide-range cassette of eleven cogs in the rear. Proponents say they are lighter and simpler and the only drawback is larger jumps between gears.

Since I got back into cycling a few years ago, I've been riding older 3x7 and 3x8 bikes. I've run different tire sizes and have seen the effect that has. Smaller tires means using the "upper half" of gears, to oversimplify the example, and fatter tires means using the "lower half" for the same speeds with similar effort.

Sometimes I would use every gear on the 3x8 mountain bike on longer rides because there are a lot of hills where I ride and much of that is off-road trails where low gears really help.

Example:



The bike I took to the shop is sort of a jack-of-all-trades that can run skinny road tires and fatter tires that are more fun off road. I plan to do both and want to have a wide range of gears so I can climb anything and still rocket downhill on some long, straight roads without "spinning out" and having to coast. I think a 3x9 will give me all that. It will also cost much less than a full 1x11 conversion would, since all I need is a different front derailleur, a wider bottom bracket, and one extra chainring with mounting bolts.

If I were buying a brand new bike, I'd probably get something with a 1x11 drivetrain and disc brakes like this, but I'm not.