If any company ought to have this down, it should be this one. Though QR did start the 650c revolution, Cervelo has been the best at exploiting that design style. And yes, its smaller-sized tri bikes are made with 650c wheels.

The way you tell how a bike is actually going to fit you is not by top tube, or seat angle, or any of that. In a very small size you can usually get the saddle where you want it just by moving it fore and aft on the rails, as long as the seat angle is at least as steep as 76 degrees. The way you really tell whether a bike is going to fit is by its stack and its reach, that is, the horizontal and vertical distances between the bottom bracket and the top of the head tube.

The Kestrel Airfoil Pro in its smallest size has the shortest stack in the biz, at 43.7cm. If you're particularly short, and you ride with any sort of a flattish back, getting low enough may be a challenge and this measure of stack is the best way to determine the shortest bikes out there.

How does the 48cm Cervelo stack up? Or stack down, as it were? It's stack is 46.1cm, which means the Airfoil Pro sits about an inch lower (2.4cm). As they are spec'd stock, however, these bikes are about equal in "lowness" because the Kestrel comes with an aerobar style that sits higher on its pursuit bar (see our overview of Specialized for a more in-depth discussion of the Profile Design T2 Cobra). And the Cervelo really does take care of the majority of smaller folks. It's the exceptional person who'll require the Airfoil's short stature.

For the record, here are some examples: Kestrel at 43.7cm, then QR's Kilo/TQ at 45.0cm, Calfee 45.7cm, Cervelo at 46.1cm, Elite at 46.25cm, Felt at 46.5cm. These are typical numbers for well-conceived tri bikes in small sizes. Contrast that to the smallest sizes made in 700c, where it is very hard to make a bike that has a stack of less than 50cm. More typical is 51cm to 53cm. Trek's smallest Equinox TTX has a stack of 52cm. The shortest Scott Plasmas are 50.4cm, and Specialized can offer 49.4cm. That's why the 650c wheels is so critical in these smallest bikes, for the smallest riders.

What the Cervelo has that is almost unique is the faired rear wheel in its smallest sized bikes. Every model that fairs the rear wheel in 700c stays faired in 650c, that is, the P3C, P2C nd P2SL. Only the Dual is unfaired, but it is in 700c as well.

This means the 650c Cervelos enjoy the same sort of aerodynamic benefit the 700c sizes do, but still grant the rider the handling and fit qualities offered by 650c wheels. Felt is the most obvious example of a company that offers this, but after Felt and Cervelo the list gets mighty thin, mighty fast.

It is frankly silly, at this point, for the P2C to not be Cervelo's best selling tri bike, because of a little known fact: As of January 15, 2007 the price of this bike, complete, is now $3000. The only thing that makes any sense is that Cervelo is just daring its customers to buy its P3C instead, which its customers continue to do. But the P2C has 98 percent of what the P3C has, and is only two-thirds the money ($4500 to $3000). The Dura Ace blend kit is identical model-to-model, and that clever seat tube on the marvelous P3C is the chief distinguishing feature between these two fine models.

All that established, the P3C is still a formidable bike even at $4500, compared to those in its competitive set, and that remains the case in its smallest sizes. Both the P3C and P2C are built around the 650c wheelsize in their 48cm configurations and, as noted, keep their faired rear wheels.

In the case of their 48cm models, the Cervelos are not flattened versions of their taller sizes, they are proportionately smaller versions throughout. In keeping with this theme it builds this size with a very short chainstay of 368mm. This places the cassette very close to the crankset, and taxes the drivetrain to its limits as regards smooth shifting and relatively frictionless chain-to-gear interaction. Compare this to the typical road bike's chain stay of 415mm.

Remember the dropouts are horizontal, and the chain stay adjustable, so making that 368mm chainstay longer is possible (if you feel the need). Depending on how the bike shifts, one might make that 368mm into, say, a 375mm or so. Of course the tradeoff is aerodynamics -- you want the tire as close to the seat tube as possible.

Is the 368mm chain stay too short for proper shifting? Shimano says so, and fixes the minimum chain stay at 405mm. But Shimano advertises its drivetrain as rideable in all configurations, even big-to-big and small-to-small (these are gear configurations cyclists are taught to avoid). Riding small-to-small is in any case probably not achievable on this chain stay length, because the chain would certainly knick the big ring on its way to the small cog (for this and other reasons these small size Cervelos are probably ridden best with 110mm bolt pattern cranks, and the front derailleur hanger is set up to accommodate either 130mm or 110mm).

Shimano's minimum chain stay spec lept from 390mm to 405mm when going from 9sp to 10sp, and this is curious since the 10sp chain is so much more laterally flexible. If anything, these short-chain stay Cervelos should run better with the 10sp chain then they did when spec'd with 9sp. Still, big-to-big riding may cause the chain to drop inadvertently to the small ring, and small-to-small (and perhaps second-to-small) is likely to generate the "ting, ting, ting" sound of the chain hitting the big ring on its trip north from the cogset. So, don't ride the crossover gears you shouldn't be riding anyway, and consider having your retailer swap for 50x36 at the point of purchase (that might coax this bike's best performance).

With those provisos, the Cervelo in 48cm is a marvelous bike, and if this company outdistances its competitors in 700c, how much more so in the small size, where so many of tri bike makers drop out of the competition by not offering 650c?

Cervelo makes all its smallest bikes in 650c. Its Dual starts at $1500, and the P2SL at $2000. These bikes are fabulous for smaller riders, and they're available in every price point. Read more about Cervelo's tri bikes here.