Front Derailleur Installation and Adjustment

Tools needed:

5 mm hex wrench

small Phillips head screwdriver

pliers

The front derailleur shifts gears by moving the chain from one chainring (front gear) to another. One click of the indexed shifter moves the derailleur exactly enough to move the chain one chainring. Note, however, that some road shifters and twist shifters have "half stops" in the indexing for the middle chainring, allowing the derailleur to move smaller distances. Half stops allow "feathering," minute adjustments to avoid the chain rubbing against the inside of the derailleur.

Examine the derailleur and notice these features:

1. the stop (or limit) screws, which may be marked "H" and the other "L", which set the limit of the derailleur's motion to the outside and inside

2. the bolt and washer that will hold the cable to the derailleur--note that either the bolt or the washer has a little groove on the bottom where the cable is designed to fit--it is extremely important to connect the cable to the correct side of the bolt, so make sure you know which side is right.

Look at the front shifter and notice that it has a barrel adjuster. While the cable is not connected to the derailleur, pull the cable with your fingers and manipulate the shifter, imitating shifts. Notice that each click of the shifter results in either tightening or loosening the cable. Imagine that as the cable is tightened it pulls the derailleur from its default position over the small ring toward the larger rings, and that as the cable is loosened the derailleur falls from the bigger rings to the smaller ones.

If the cable does not move easily, replace the cable or housing.

The steps to install a new front derailleur are:

1. Remove the old derailleur:

a. remove the chain

b. disconnect the cable

c. unbolt the derailleur (some derailleurs are attached to the bottom bracket, requiring the removal of the right hand crank).

2. Clean everything you can reach.

3. Bolt on the new derailleur, leaving it loose enough to move.

4. Install the chain. The chain will be on the small chainring.

5. Position the derailleur correctly. The outside plate must be the correct height above the big chainring and parallel to it.

a. Position the outside plate of the derailleur 1-2 mm above the big chainring. Many derailleurs come with a taped-on guide for this step. Usually, the closer the derailleur to the chainring the better.

Position Outside Plate 1-2 mm above Big Ring

b. Angle the outside of the outside plate of the derailleur so it is exactly parallel to the big chainring. This can be confusing, because the outside plate is often not straight. This is the step most often screwed up, so if you have shifting problems look first to this angle.

Position Outside Plate Parallel to Rings

c. Tighten the the derailleur attachment bolt tight enough for it to stay put, but not so tight as to strip it or damage the frame.

6. Set the L stop screw. "L" stands for low gear, which is the smallest chainring--the most inside ring. If you can't tell which stop screw is which, manipulate them. The one that moves the derailleur when it is in its natural position (low gear) is the L stop.

a. Shift the rear derailleur so the chain is on the low cog--the biggest cog on the rear--the one that is the most inside.

b. The front derailleur must be on the low chainring--the smallest ring on the front--the one that is the most inside.

c. Twist the L stop screw until the inside plate of the derailleur almost touches the chain. You want the chain to easily shift in to the small ring but never come off to the inside.

Adjust L Stop Limit Screw--Inside Plate Close to Chain

7. Adjust every barrel adjuster between the front derailleur and the shifter by advancing them clockwise until they are shut, and then rotating them counterclockwise one rotation. Road bikes may have a barrel adjuster on the cable-line attached to the frame.

8. Shift in to the lowest gear (the position  where as much cable as possible is let out from the shifter). The chain must be on the small chainring.

9. Attach the cable to the derailleur. The cable attachment bolt, or its washer, will have a groove on the bottom where the cable is intended to run. Attach the cable at the exact correct place--if you do not your shifting will suck. Before tightening the bolt, pull the cable tight with your fingers (some mechanics prefer to pull the cable with pliers), trying not to move the derailleur in the process.

10. Set the H stop screw. "H" stands for high gear, which is the largest chainring--the most outside ring.

a. Shift the rear derailleur so the chain is on the high cog--the smallest cog that is the most outside.

b. Shift the front derailleur so the chain to the big chainring.

c. Pull on the cable with your free hand while pedaling. If the chain comes off the big chainring, or if the chain won't shift to the big chainring, the H stop needs adjustment. Twist the H stop screw until the inner surface of the outside plate of the derailleur almost touches the chain when it is in the big chainring. You want the chain to easily shift to the big ring but never come off to the outside, no matter how hard you pull the cable with your hand.

Adjust H Stop Limit Screw--Outside Plate Close to Chain

11. Make adjustments for smooth shifting in to each gear.

a. Shift to the small chainring, with the rear derailleur in a middle cog. Push the front shifter one click. If the chain does not go in to the next ring, twist the barrel adjuster counterclockwise to tighten the cable until you get your shift. If you have to extend the barrel adjuster almost to its end, stop. Return the barrel adjuster to its original position (all the way clockwise, then one rotation counterclockwise), and retighten the cable at the derailleur. Adjust chain tension until shifting to each gear is smooth.

b. While in the middle chainring, shift through all the rear gears. There should be no chain rub. If there is, adjust cable tension, or re-examine whether the derailleur is in the proper position.

c. Shift many times. You may adjust the stop screws so the shift to the extreme gears is easy, but be sure the chain won't come off.

12. Test and stress the system by shifting a lot of times, and test ride your bike. Tweak as necessary. If you have trouble, you are not alone. The front derailleur is the hardest component to get to work right.

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