Last Part - 3 of 3 - How to Custom Fit Your Bike

Top Tube and Stem Length

Next, dial in the correct "reach" to the bar, or horizontal fit. Proper reach gives you easier breathing, better neck and lower back comfort, and better weight distribution and bike handling.
That "ideal position" varies here more than anywhere else for cyclists, depending on riding style, flexibility, body proportions, and frame geometry, among others. And, your upper body position will evolve with more hours in the saddle. That is, you may find that you develop a lower, longer position as your fitness and flexibility improve. As Davis Phinney notes, though it may be difficult to achieve a truly flat back, we cyclists should all strive to be “longer” across the top of the bike.

Unfortunately, there is no formula for sizing the top tube and stem that works as well as the inseam method. One indicator comes from glancing down at the front hub while riding in the drops; your view of the front hub should be obstructed by the handlebar. LeMond recommends that your elbows, bent at 65–70° with your hands in the drops, should be within an inch or two of your knees at the top of your stroke.

Measure your current bike’s top tube and stem. Then, decide how you’d like to alter that fit; add the top tube length to the stem length to get your overall top dimension. This is the very reason why stems come in 1cm increments from 7cm to 14cm, just to let you dial in your best top tube and stem length.

Handlebar Size

Road handlebars come in several widths and bends. Most cyclists select a bar that is just as wide as their shoulders, measured as the distance between the shoulder joints. A wider bar opens the chest for better breathing and more leverage, but is less aerodynamic. You’ll need to find your own balance between the two.

Crank Length, Gearing

Choosing the right crank arm length, like the rest of this, comes down to your size and riding style. Longer cranks give you more leverage, helpful if you like to push big gears at a low cadence (climbing, time trialing, etc.). On the other hand, if you like to spin at a high cadence, you’ll do better with standard cranks. As a starting point, we often recommend 170mm cranks on 54cm C-T road frames and smaller, 170–172.5mm cranks on 55–61cm frames, and 172.5–175mm cranks on 62cm frames and larger.

We offer a wide range of gearing options for chainrings and cassettes. Depending on your strength and terrain, you’re welcome to specify the close-ratio gearing generally used for racing, or wider ratios for hilly terrain or more recreational riding.