Aside from your frameset, the wheels are probably the next most expensive structural part of your bike. In fact, I have a friend who bought a $1200 Cannondale, and then spend another $1200 a year later to replace the stock wheels to an expensive set of Reynolds carbon rims. I can’t afford a set of Zipp or Reynolds or Easton carbon rims, in fact, I can’t even afford a set of high-end Mavic alloy rims, but I nevertheless want to have carbon wheels.
eBay to the rescue! Actually, aside from eBay, actually, most carbon frame manufacturers also make carbon bike wheels, and often you can order them directly from their websites. Expect to pay about $400-$550 USD, depending on what you need. You’ll notice from my collection of photos of other people’s bikes on my front page that most carbon bike builders prefer having “deep dish” wheels. Rims with deep sections are very cool to look at, but remember a 50mm rim will always be heavier and slightly more expensive than a 38mm rim, so if you like climbing hills, you may want to go with something lighter, Also, the deeper the rim, the more susceptible they are to crosswinds, so my suggestion is to not get the 80mm rims unless it’s for the rear wheel of your time-trial bike. A set of 50mm wheels weighs about 1500-1700g, including the hub and quick-release skewers, but they usually don’t come with rim tape, and you have to put those in yourself.
Tip: if you have 50mm rims on your bike, make sure that your spare tubes have a long valve stem, or you have a valve extender. And make sure you carry them with you on every ride. Chances are, if you get in trouble on the road, your fellow riders won’t have a valve stem that’s long enough.
Now that we’ve talked about the depth of the rim, another thing to pay attention to is the width of the rim. Most are 18-20mm wide and they’re perfect for 700c x 23 tires. But more and more people have switched to 700c x 25 tires for comfort (new studies suggest that because the new tires can maintain higher tire pressures, even though they’re slightly wider, their rolling resistance is comparable to the skinnier 23mm tires) and if that’s what you prefer, there are newer carbon rims out there that is 25mm wide.
Tip: if you prefer riding wider tires, your wheels may have no problems with them, but make sure your frame and brakes have enough clearance for the wider tire.
Another, perhaps slightly less important, issue to consider is the profile shape of the rim. Most carbon rims that you can find have the traditional “V” shape, and that’s what I have on my bike too. But increasingly there are studies that show that a more oval design (like the Zipp Firecrest profile on the figure on the left) are actually more aerodynamic, especially in crosswind conditions. I have looked at a lot of vendors of carbon wheels online, and most do not mention what kind of profile their wheels have, so you may have to look very closely at the photos, and hope that whatever wheels that the vendor send over from China has the same profile as in the photos. The only place I know of that explicitly mentions that their carbon rims have an oval profile is on VeloBuild.com. The customer reviews of this site is mixed, and I don’t know enough about the company to give a fair assessment.
The carbon wheels from China usually have Novatec road hubs (made in China of course). The online reviews of these hubs are mixed: they range from “wow, so light and so cheap, where have you been all my life?” to “they’re pieces of s*** and not worth the $50 that I paid”. My own experience is that yes, they’re inexpensive, incredibly light, and they perform very well on my bike. (One trick that I show people is that I mount my bike on my repair stand, and then spin up my front wheel with my hands. It spins for much longer than anything else that I have.) But I also have one unpleasant experience. During a climb at a charity event, the smallest cog from my SRAM cassette broke free. The centre of the cog ripped right through the splines on the hub shell: I pedalled, but the wheels would not spin. I fell off my bike, and it was very embarrassing. My fix was to replace the cassette with a more expensive Shimano Ultegra cassette that has a stronger one-piece body. Other than that, overall I have been very impressed by the Novatec hubs in the 3 years that I had been using them. Some listing on eBay have wheels that use Powerway hubs (also made in China?) which are slightly more expensive. I have absolutely no experience with these hubs, and I welcome anyone with knowledge to give me some feedback.
Pay attention to cassette compatibility. Obviously Campagnolo hubs don’t fit Shimano or SRAM cassettes and vice versa. Aside from that, most new hubs should be 11-speed compatible, since the Shimano Dura-Ace, Ultegra and 105 series groupsets have have gone 11-speed. Those hubs are still backward compatible with 8/9/10 speed groupsets (Shimano Tiagra, Sora and Claris groupsets) with a special spacer, but the reverse isn’t true.
Pay attention to hub spacing. This is especially true if you have a disc-brake frameset. The front hub width is 100mm for both disc and conventional rim brakes, but the rear can be either 130mm or 135mm.