Bike handlebar height is a matter of personal preference that largely depends on your riding style. For example, recreational riders usually prefer a slightly higher position, while speed racers like to enhance their aerodynamics by setting the bars much lower. Whatever your cycling interest, handlebar height is important to your comfort while riding. Having the handlebars at an incorrect height can result in an uncomfortable riding position and possible injury.
Look for a small bolt on the top of the carbon handlebar stem. Sometimes the bolt head is hidden by a small, domed plastic cover. If the bolt on your bike has a cover, gently pry it off using a flat-head screwdriver or a butter knife.
Turn the bolt until it is loose, but not completely free from the stem. Most bikes require a 6mm Allen wrench to turn the bolt. You may need to experiment with different-size Allen wrenches to get the right fit. If you loosen the bolt and the handlebars won't budge, tap the head of the bolt gently with the mallet until it pops back into the stem. The handlebars should now be loose.
Pull or push your handlebars up or down until they are at the height you desire. Most bikes have a guideline on the stem that indicates the upper limit for the handlebar height. These guidelines are in place for safety reasons; do not extend the handlebars past this point.
Tighten the bolt again, making sure the bicycle handlebars are straight before doing so.
Tips & Warnings
If you can't see a bolt on your bike's stem, you may have a threaded stem. These are much more difficult to adjust, and often can be readjusted only by cutting part of the stem, fixing the height of the handlebars permanently. Consult your nearest bicycle shop.