Handlebar extensions (also known as bar ends) will improve your comfort on the bike and boost your climbing ability. Installing them yourself will save you some money.
Loosen the bolts on the shifters and brake levers.
Make a mental note of the angle at which your shifters and brake levers were attached.
Move the shifters and brake levers toward the center of the handlebars.
Remove the grips. See "Replace Bike Grips," under Related eHows.
You will need to cut the ends of the grips before you reinstall them. Many grips will have a marked groove that you can cut with scissors.
Reinstall the grips, sliding them far enough onto the bar to allow room for your bar ends.
Install the bar ends. Tighten them with a 5-mm Allen wrench. Be careful not to overtighten them, as you can damage the bar.
Reposition the shifters and brake levers, and tighten their bolts.
You may find you need to readjust the angle of your bar ends after a test ride. Experiment until you find a location that is comfortable for you.