By Eric Hagerman

Unless you've already figured out exactly what size bike you need, including reach, saddle height, and saddle position, visit a shop with a good service department (and one that carries a minimum of four brands) and ask to be sized. While this step is important when buying a mountain bike too, it's absolutely crucial with road bikes, because you'll be spending a lot of time in one position, meaning that position better be right. The best shops will have something called a fit-kit--an adjustable bike frame that looks like it was made from a life-size Erector Set--and they'll be willing to invest the time to size you up. Once you know the dimensions, here are the other major factors to consider.

Frame Geometry
There are four basic types of road frames. Triathlon bikes are upright (steep seat- and head-tube angles) and skittish but allow great power output. Criterium bikes have short, tight wheelbases and are stiff and responsive. A traditional road-racing frame is "laid back," meaning the seat- and head-tube angles are somewhere between 71 degrees and 73.5 degrees. This is the best balance between comfort and responsiveness. A touring bike is similarly laid back--possibly more so--and has a longer wheelbase, which allows for steady, hands-free cruising and better handling under a heavy load. Consider the first two only if your trip has a competitive aspect; if you're hauling your own gear using panniers (essentially a backpack for your bike), a touring bike is the best option. For all other trips--meaning your average sag-wagon-supported, enjoy-the-scenery journey--a traditional road bike will probably do the trick.

Frame Material
The frame is what gives a bike its ride quality, so get the best one your budget will allow. With aluminum and steel (often "cromoly") frames, this means making sure the tubes are "butted"--thin at the middle to save weight and thick at the joints for the requisite strength. Don't let anyone tell you that an aluminum frame is by definition lighter and stronger than steel--both can offer light, resilient rides, though all things being equal, aluminum is stiffer and cromoly more lively. Titanium, the metal of choice among connoisseurs, is lighter and stiffer than both and will never rust, but will put a heftier dent in your pocketbook. Finally, there's carbon fiber, which really deserves a category unto itself. It can be even lighter than titanium, stiffer than aluminum, and more comfortable than steel. But it's also superexpensive and essentially a glorified form of plastic, making it somewhat less durable than the other alternatives.

Fork
Bikes come with steel (cromoly), aluminum, or carbon-fiber forks, in order of price. Your choice will have a huge impact on the comfort of your ride and the handling of your bike, since the fork transmits road vibrations through your handlebars. Aluminum is stiff and offers precise steering, but it's uncomfortable and the least desirable. Steel is far more comfortable but likely heavier. Carbon fiber is sweet: comfortable yet stiff; light yet strong; plastic yet expensive.

Wheels
The lighter you are, the lighter your wheels can be. And light is good when it comes to rotating weight, which acts heavier than stationary weight because it takes extra effort to spin it up to speed. Your wheels should have aluminum rims, aluminum spoke nipples, and double-butted spokes. Beyond those baseline features, look for wheels with fewer than 32 spokes (assuming you're not a heavyweight). Make sure that the shop will re-true your wheels after your first 100 miles.

Crank
If you're going to be riding hills, shelve your pride and get a triple chainring crank. Doubles, of course, are lighter--and don't elicit macho sneers from the pros--but for most of us, there will be times when you simply need the extra oomph you can only get from a "granny gear."

Shifting Campagnolo or Shimano--same difference. At least in terms of performance. Traditionalists tend to prefer Campy; techies, Shimano. Shimano tends to be less expensive but less stylish.

Handlebars
They should be as wide as the distance between your two shoulder joints.

Eric Hagerman is senior editor of Outside magazine.