There a couple ways you can go about getting an Xtracycle.
A) You can choose a pre-built Xtracycle (that includes a bike) from their website.
b) You can just buy the Free Radical/Free Loader kit (the frame & rack) and attach it to a bike you already have.
C) If you don't have a (suitable) bike you can buy a pre-built (used or new) bike & attach the kit.
d) If you don't have a (suitable) bike you can buy a frame, components etc, to build up a bike that is ideal for an Xtracycle kit.
This post is about option (d). Choosing a suitable (and by suitable, I really mean 'ideal', because most bikes will work just fine for an Xtracycle) bicycle. And so it begins..
i. On frames..
If you're going to spend money anywhere, spend it on your frame. If you're going to get a headache over anything, get it over your frame. Your frame has the greatest impact on how your bike fits you, performs, and lifespan of your bike (you might still be riding it at 85!). Other things (handlebars, stem, seatpost, wheels etc) are much easier (and usually cheaper) to change. But don't get a headache. Nobody likes a headache.
STEP ONE: frame material
Choosing a frame begins with frame material. Generally, you'll be deciding between steel or aluminum (or a mix) since anything else (carbon) is really just for Fancy Pants Racing or Fancy Pants Racing Wannabes. & you're not looking to race, you're looking for something strong, durable & comfortable (as opposed to light, fast & aerodynamic).
Steel PROS: To quote Surly, "plentiful, durable, repairable and easily recyclable." Also cheap & dampens vibration wonderfully. (Imagine a 10hr car ride in a jeep vs. a luxury car.)
Steel CONS: Heavy. Some say rust, but that's easily preventable & even fixable.
Aluminum PROS: Cheap, light, stiff (stiff is good for power transfer, which is good for speed).
Aluminum CONS: Not so repairable. Imagine a pop can. Imagine putting a dent in the pop can. Now the pop can will easily crush.
Further reading on frame materials, particularly steel: Sheldon Brown, Surly, Rivendell.
So if you haven't noticed my bias already- I like steel. But really, aluminum is great, too- and just because a bike is aluminum, that should not be the sole reason to shy away from it. My race bike is aluminum & carbon.
STEP TWO: frame design
The geometry of a bike has influence not only on how the bike handles (zippy vs stable etc) but also on how your body handles the bike! (sore back vs happy back etc.) Let's go from one extreme to the other.
Racing time trial bike: more about aerodynamics than comfort.
Racing road bike: an 'aggressive' position, bending your back to reach the bars.
Touring road bike: a more relaxed position, but still bending a little bit.
Commuter hybrid: sitting much more upright, leaning forward only a little bit.
'Bike Path' bike: sitting very upright, hardly leaning forward at all.
Cruiser bike: like sitting on a couch.
The range that would be appropriate for an Xtracycle is anywhere between Touring & Cruiser. Where you fall in that spectrum depends on what you're comfortable with and what you intend to use your Xtracycle for.
If you want to use your Xtra as your primary commuting vehicle, but also go bicycle camping/touring on it.. if you're a roadie and can't get away from drop bars.. if you're more comfortable/accustomed to a road bike geometry than mountain.. my suggestion is a touring frame/bike.
Suggestions: Surly Long Haul Trucker
*That's my Surly Long Haul Trucker haulin' some pizza in that photo! I used the cardboard box that shipped my wideloaders. :)
If you want to use your Xtra as your primary commuting vehicle, not just downtown but also for longer distances.. my suggestion is a commuter/hybrid frame/bike.
Suggestions: Surly Big Dummy w/ flat bars, Marin Novato offered by Xtracycle, Jamis Coda Sport
If you want to use your Xtra as your frequent commuting vehicle, but aren't interested in terrifically large loads, going fast or going far.. if you're more comfortable/accustomed to upright mountain geometry than road.. my suggestion is a bike path or mountain frame/bike.
Suggestions: Surly Big Dummy w/ cruiser bars, Surly Instigator, Jamis Commuter
*An added advantage of Surly's Big Dummy (frame in the photo above right, full build with flat bars in the photo to the left) that it is the only frame actually that actually integrates Xtracycle's racks (Free Loaders) into its design. The benefits include a better ride & durability. Not to mention the cool factor.
If you want to use your Xtra as your frequent commuting vehicle, but only for short distances and at leisure speed.. if you plan on installing speakers, a keg & neon lights on the back.. my suggestion is a cruiser frame/bike.
Suggestions: Electra Townie offered by Xtracycle
STEP THREE: deciding everything else
All the other pieces are good to think about, and some are more important than others (your wheels are more important than your seat post, for example). So if you're going to spec' out your bike part by part, first you want to be familiar with what has priority for quality and where you can get away with.. less than quality. Here is my list in order of priority & my two cents on each.
Level One Priority
Wheels
Your rear wheel in particular needs to be strong in order to support heavy loads. A weak or poorly built wheel will go easily out of true (wobble), break spokes or even just fail (turn into a taco shell instead of a round wheel). A wheel can be made strong by its rim design (a cyclocross wheel which is meant for rough riding would be designed for strength) but also its spoke count & pattern. Tandems, for example, have to support a lot of weight so their wheels often have 42+ spokes instead of 32. My rear wheel has 32 but uses a "3-cross" pattern where each spoke crosses another 2-3 times instead of crossing 0-1 times like my race wheels (which don't have to support as much weight and can afford to be "aerodynamic").
What I have: Mavic XC 717 Cross Rims 32h 3-cross pattern
Brakes
Brakes are always important for safety, but they're extra important when you're carrying a load & riding in traffic. The advantage of disc brakes is that they perform just as well in wet weather, but they can be a pain to fix (especially if you plan to travel in remote places)- so unless you live in a rainy & hilly area, they're not necessary. V-brakes & Cantilevers, both found commonly on mountain bikes & some road bikes (e.g. cyclocross), are very strong & easy to repair. Caliper brakes, found on road racing bikes, are not very strong but okay if you're not carrying heavy loads.
What I have: Avid Brakes
Handle Bars
While the quality of handle bars may not matter so much (you're not trying to win a sprint finish in the Tour de France, are you?), the shape will vastly affect your comfort & how the bike handles. Drop bars provide not only an aerodynamic position, but several positions, which makes it beneficial for touring. However, your hands will be much closer to the center which may make large loads trickier to manage. Flat bars are nice in that they spread your arms wider and make loads easier to manage, but you don't have nearly as many options for hand positions. Cruiser bars are fun and allow you to sit completely upright, but I personally find them hard to maneuver (probably because I'm a roadie). If you don't have experience with a particular bar (drop bars, for example), they're bound to feel very strange at first- but give them a chance (say, borrow a friend's bike) and you can usually develop a feel for them.
What I have: Ritchey Biomax drop bars
Saddle
Don't skimp here! This is your butt & your happiness we're talking about. But in searching for comfort, be aware that softer does not always mean better. Large & soft seats are good for cruisers which typically don't go on very long rides. Think of a saddle like a mattress. A really soft mattress feels great for a few minutes, but sleep on it all night and you'll have no support and feel sore in the morning. Likewise, sleeping on concrete doesn't do you any good either.
What I have: Terry
Cassette/Chain Rings
What matters here is a range of gears. While some purist Cool Cats like riding Xtracycles on single speeds (which is more about culture than about practical, if you ask me), it makes much more sense to have easy gears readily available for hauling large loads, especially up hills. I have a 46/?/26 triple up front and a 12-26 in the rear. So far, so good.
Also, I have a 9 speed as opposed to a 10 speed so that I can have a wider and thus more durable chain that is more widely available.
What I have: 46/?/26 triple up front, 12-16 in the rear
Level Two Priority
Headset
The headset is what holds your fork onto your frame and allows it to rotate. Riding on bumpy roads can put stress & wear on the headset. Because I want to not only commute, but also to explore on my bike, I chose a Chris King headset which is the "bling" of headsets. It's what you might call "over-manufactured," which means that it could undergo much tougher conditions than a bike could ever provide. Pretty much it could be your last headset. The downside is that they're really expensive. You can justify it, though, by thinking of buying a Chris King like buying the time of 2 or more regular headsets.
What I have: Chris King.. in pink
Bottom Bracket
The bottom bracket is the moving part that is between your two cranks. Same deal with the headset, only different name. I got a Phil Wood, another expensive and over-manufactured part so that I won't have to ever worry about what's goin' on down there.
What I have: Phil Wood
Wheel Hubs
The wheel hub is the moving part of your wheel, where all of the spokes meet. Generally, (as with the headset & bottom bracket) moving parts are what get a lot of wear on your bike and are worth investing in. This rule doesn't always apply, though- since a chain moves a lot, but is replaced the most and thus may not be worth spending extra money on each time.
What I have: Shimano XT
Rear Derailleur
The rear (arguably) is more important than the front since it is a more complicated mechanism & has more gears to change.
What I have: Shimano 105
Tires
Unless you live in the mountains, you don't need knobby mountain tires. They not only slow you down, they make riding more work. There are lots of great city tires out there that are mostly smooth (they usually have an indented pattern) and not too skinny (you want at least 1.5" wide unless you don't plan on carrying heavy loads).
What I have: Panaracer Pasela Touring 1.5"
Level Three Priority
Shifters
I chose bar-end shifters for their simplicity so that they'd be easy to repair 'in the field'. Any manual shifter will also be cheaper. An STI shifter, which basically means things shifters that go 'click!' 'click!' and ta-da, you've shifted- are very nice to use, but more expensive & have lots of internal parts. Note that 'manual' shifters do have the option to go 'click!' 'click!' but can easily be converted to friction shifting which is when you slowly turn the lever until the gears have shifted.
What I have: Shimano bar-end
Pedals
I got some cheap, but awesome platforms that look simple and grip great. Don't need bike shoes, just any shoes.
What I have: MKS Touring pedals
Stem
The quality isn't so important, but the size & angle are very important. This decides much of your body positioning on the bike.
Epilogue. How I chose the Surly Long Haul Trucker.
I wanted to tour on my bike as well as commute/haul, which lead me to consider touring bikes. I also wanted control over each part, which lead me to consider choosing a touring frame instead of a complete bike. I also wanted it to be made out of steel for repairability, durability & longevity, so that narrowed down the options some more. Then I wanted a no-frills, straightforward company that was environmentally responsible as well as affordable. And a sweet understated color. Thus was born the Surly Long Haul Trucker. Surly, in general, provides well-crafted steel frames that are smartly designed without the overhead spent on mass marketing, savings which transfer to your pocket book. I recommend them.
