How to Change a Road Bike's Rear Derailleur

How to Change a Road Bike's Rear Derailleur
After years of wear and tear, you might need to change your bike's rear derailleur. After purchasing a new derailleur, you can install it at home yourself with no need to leave your bike at the bike shop. Learning to change out the parts on your bike is one of the best ways to learn the ins and outs of your bike and how to maintain it properly so you can count on it for years to come.
 

Instructions

Difficulty: Moderate

Things You’ll Need:
  • Bike
  • 5mm Allen Key or three way multitool
  • Rear derailleur
  • Cable
  • Grease
 
Step 1
Take the cable out of your old derailleur by loosening the cable with a 5mm Allen key. Pull it out of the rear derailleur. Loosen the rear derailleur from the rear hanger by placing your Allen key or three-way multitool into the Allen head. Make sure to pull the old rear derailleur toward the back of the bike to reduce tension and keep from tearing up the threads on the hanger.
Step 2
After removing the old rear derailleur, clean out the threads on the rear derailleur hanger before you put the new derailleur on. Put an even coat of grease around the threads on the top back side of the new rear derailleur. These are the threads that you will thread into the derailleur hanger, so you want to make sure that it is greased. The grease will help prevent future creaking and rust.
Step 3
Hold the new rear derailleur so the words on the front plate are facing diagonally. With the 5mm Allen key or three-way multitool, start to screw in the rear derailleur to the hanger on the frame. The threads on the rear derailleur hanger start at an angle. You should feel the derailleur screwing in smoothly. Screw down the rear derailleur tightly so it won't come loose.
Step 4
Thread the cable through the barrel adjuster, the round plastic piece. This will lead the cable out and through to the cable guide. Pull the cable through all the way until it is tight and there is no slack in the cable. Then you need to check your limits. The limit adjustments keep the derailleur from shifting too high and going into your spokes, or too low and into your frame. The adjustments are made by screwing down the two screws on the outside of the derailleur, labeled H for the high limit and L for the low limit. If the derailleur is shifting into your spokes, turn the screw with the H down a quarter of a turn at a time until it is no longer going too far. If it will not shift into the highest cog, loosen the screw a quarter of a turn until it is throwing the chain to the highest cog, but not into the spokes. Repeat this process for the low gear limit, loosening it to get the full range of cogs and tightening it down if it is going into the frame.
Step 5
Loosen up the cable after adjusting the limit screws. Do one last final pull so the cable is tighter and then tighten it down. You need to do this because as you adjust the limit screws it affects the cable tension.
Step 6
Run through the gears one more time and you are good to go.
 

Article Written By Courtney Johnson

Courtney Johnson is a freelance sports writer and photographer based in California. Her articles and photos appear regularly in newspapers and magazines such as "Triathlete" and "Cross Country Skier." Johnson graduated from the University of Iowa with a B.A. in media production and minor in writing. She is studying for her copy editing certificate at the University of San Diego.

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