Let’s start with the frame, because, well, where else would you start? (If you’re missing a wheel, you have “a bike with a missing wheel”; if you’re missing a frame, you can’t even say that you have bike at all.) A typical unbranded carbon frameset (frame and fork) sells for $500-$700 USD (including shipping) online, depending on the frame design and the vendor. Here are a few things to look for:
(Frame) size matters. Getting the right size is absolutely the most important, and it’s also the most difficult part of buying a frame online. Riding a road bike that is too big or too small can be very uncomfortable. As a guide line, I am a very-average 175cm (5’9″) tall, and I ride a “54cm” frame with an effective top-tube length of 545mm. A friend of mine who is 5’3″ rides a “52cm” with effective T-T of 520mm, while another friend who is 6’2″ rides a “60cm” Cannondale frame that he finds a bit too small. I put the frame sizes in quotation marks because there is no standard in measuring frame size, although it usually (albeit not always) refer to the seat tube length (“B” in the figure on the right). With different top tube geometries out there, the effective top-tube length (“A” on the figure) is perhaps a better guide. If you are still uncertain, you can always ask the vendor which size suits you best (you will need to tell him your height and in-seam length, and if you don’t get a satisfactory answer, well, choose another with better customer service! Bear in mind though, after you build up your bike, you will still need to do a “fitting”—that’s when the length and height of the stem and the location of the saddle etc will be adjusted. It’s okay if your frame is slightly too big or too small.
“Preview” the final product. Plenty of people posts pictures of their treasured carbon bikes after they build them. Once you think you have the frame that you want, doing an image search can give you a good idea of what the final product will look like. I will talk more about this in my example. While at it, search for reviews about the frame and the vendor too. My guess is that you’ll mostly find positive comments about the frames, but sometimes you may also get some negative reviews on the vendor.
Decide on the finish. This is totally a personal preference, as the top layer of carbon is mostly for cosmetics and does not serve significant structural purposes. The finish can be either glossy or matte, with a 3K, 12K or UD (i.e. uni-directional) weave. On the right is an example (from an image that I grabbed online) of a glossy finish for all 3 types of weaves. In the UD finish you can’t really see the carbon fibres themselves; it looks like a solid piece of carbon. In contrast, the 12K finish looks like it’s fake (believe me, it’s not), while the 3K finish is what you’d expect from a carbon fibre cloth. I think currently it’s most fashionable to get a matte 3D or UD finish (this is the finish on my own bike, so I am definitely biased. That said, my bike had quickly earned the nickname “Bat-mobike” for its resemblance to Batman’s gear) although some discussions on forums suggest that the clear glossy finish may be more durable and more resistant to scratches.
On the left is another example that I found online. And yes, there is a typo and that’s not meant to be someone’s name. Most carbon bike frame factories are located in Shenzhen, China (it’s the city just north of Hong Kong); for some reason, most people there have trouble spelling “matte”. When you look for frames, you’ll see a lot of “Matt finish”. In fact, you’ll get better search results on eBay if you include the typo.
Know what is included. Many listings on eBay include headset bearings, and some also includes the seat post and seat post clamp.
If they’re included, great—now you have fewer things to buy and worry about. If they’re not included, then you’ll need to find out their sizes and buy them separately. The listing usually tells you the size of the components. Pay attention to that; waiting two weeks to have a clamp shipped to you from Taiwan and then finding out that it’s the wrong size sucks.
Decide on the bottom bracket (“BB”) standard. If you already have a crankset, or you are using a crankset from another bike, then this has been decided for you. Otherwise, you have some decisions to make. (This is a bit weird if you’re unfamiliar with bike parts.) Common BB standards include BSA, BB30, BB86, PF30, among others. There is a nice article on BikeRadar if you need to know what each bottom bracket means. If you want the simplest and most serviceable one, pick BSA. But your bike will not likely to be the lightest. The other standards use “press-fit” bottom brackets that are lighter, but will most likely need a special tool for installation. If you have that tool, great, if not, you’ll have to pay a few dollars for your local bike shop to install it for you.
To summarize, use this checklist when you find a frame that you like:
- Find out what size you should get. Contact vendor if necessary.
- Do a google image search. Have people built up bikes with that frame before? Does it look good? Yes: proceed. No: stop.
- Decide on a finish: 3K, 12K, UD, matte or glossy. Does the vendor sell that particular set up?
- Does it come with a seat post? Yes: proceed. No: find out seatpost diameter.
- Does it come with a seat post clamp: Yes: proceed. No: find out seatpost clamp diameter.
- Does it come with a headset? Yes: proceed. No: find out what size headset it uses.
- Find out what bottom bracket it uses.
- Find out what front derailleur it uses. (Does it require a clamp? Or is there a braze-on?)