Considering Crank Arm Length

ДИВ/

The crank arm determines the circumference in which the pedals rotate. The larger the crank arm, the larger the circumference in which you’ll be pedal­ing. A longer crank arm gives you more leverage when you pedal. Riding with a longer crank arm is kind of like being in a lower gear, an important benefit if you’re doing a lot of climbing. On the other hand, a shorter crank arm comes in handy if you pedal at a high cadence (for example, if you’re racing).

With longer crank arms it’s important to make sure the bottom bracket has enough clearance. If you buy a bike with a crank arm that’s too long, the crank arm may hit the ground when you’re cornering.

Your height will impact the length of the crank arm you chose. In most cases, taller bikers should have longer crank arms, and shorter bikers should have shorter crank arms.

A number of different crank arm lengths are available. It’s common to see lengths of 165mm to 180mm in 2.5mm increments, with the most common lengths being 170mm and 172.5mm. If you’re in the NBA, you’ll be glad to know that a few manufacturers will sell you a crank of 185mm or more. Work with your local bike store to find the crank the best suits you.

Going for Gearing

Choosing the appropriate gearing may not be fitting a bike in the traditional sense, but it is an important factor in how well a bike fits the way you ride.

By selecting a bike with the gearing that meets your fitness levels, how you pedal, and the terrain on which you ride, you can make a significant and posi­tive impact on your riding experience.

Most newer bikes have seven to ten cogs in the rear and two to three chainrings in the front. Multiply these two numbers together and you have the total number of gears for your bike. If you’re in shape and you don’t do a lot of climbing, you’re probably fine with seven to eight cogs and two chainrings. Some riders like to have a third chainring in case a climb is neces­sary or fatigue sets in at the end of a long ride (though that third chainring does add extra weight and three chainrings won’t shift as effortlessly as two); third chainrings are also useful for mountain biking and touring.

If you’re planning on doing a lot of mountain biking or touring, talk to your local bike shop to make sure you have the right gearing. They can give you advice not just about the total number of gears but about the size of the indi­vidual cogs and chainrings, important factors in gearing. (For a more detailed discussion of gearing, turn to Chapter 2.)