Sizing Cannondales, a range of road bikes known for quality and innovative design, involves standard sizing techniques as well as Cannondale-specific adjustments. Cannondales tend to have longer top tubes than other manufacturers, such that a 50 cm Cannondale frame tends to differ slightly from a 50 cm Trek, Specialized or Gary Fisher bicycle, notes Simone Jowett, manager of the Bike Doctor of Linthicum, a Maryland independent bike retailer. Longer top tubes mean that Cannondales need sizing modifications for short-torso riders.
Take your inseam measurement to arrive at a general frame size. Stand against a wall with a book between your legs pressed firmly against your crotch, to simulate the pressure of a bike seat. Have a friend measure from the floor up to the top of the book using a tape measure.
Convert the result from inches into centimeters by multiplying by 2.54 and rounding the result. An inseam of 29 inches, for example, converts to 74 cm.
Multiply your inseam by 0.67 to get an estimated frame size, which is based on the length of the seat tube. For this example of an inseam of 74 cm, the approximate frame size would be 49 cm.
Mount a Cannondale road bike model in the estimated frame size on a stand at an independent bicycle retailer so the staff can evaluate whether you have a good fit based on a long torso or need to go down a size based on a short torso. Have the staff look at your reach toward the handlebars and make fine adjustments to the handlebar stem length and the seat height.
Ride the adjusted Cannondale road bike to check the size and the adjustments and check if the bike feels comfortable. Ask the bike fitter to ride with you to check the angle of your torso and arms and to discuss any possible changes.