Front Derailleur Adjustment

Pre Adjustment Inspection

Abbreviations:

FD = Front Derailleur

CW = Clockwise

CCW = Counter Clockwise

Check that the FD Cable Housing has no kinks, sharp bends or damage.

Check that the FD Cage has no abnormal bends or damage. Note that many newer front derailleurs have oddly shaped cages. Derailleurs designed for triple cranksets may have many different bends.

The FD shown at left has specially shaped cageplates.

Make sure the FD Shifter operates smoothly and has no damage.

The chainrings should spin smoothly with no bends or missing teeth.

Note that many newer chainrings have some oddly shaped teeth. These are a design feature to smooth out shifting. The oddly shaped teeth will generally repeat two to four times on one chainring.

FD Height: The bottom of the FD cage should be 1-1.5mm above the highest tooth on the biggest chainring.
(Rotate the chainring a full revolution to check for the narrowest gap.)

Move the FD outside cage plate over the biggest chainring to check this gap.

You can do this with the shifter, or by pulling the FD cage towards the biggest chainring by hand.

FD Angle: The outside cageplate should be parallel to the biggest chainring.

Set the chain on the middle chainring, and sight from the top of the FD down towards the biggest chainring.

Adjustment

Step 1: Set FD Height and Angle (if necessary)

Shift the FD shifter to lowest gear. Turn front derailleur shifter barrel adjuster fully CW.

Loosen the FD cable anchor nut until the cable is free to move.

This will allow the FD to go into its resting position, which is typically all the way toward the frame of the bike.
(Note: Some types of FDs rest in the opposite direction.)

This is also required to allow free adjustment of the FD after the FD mounting clamp is loosened.

Loosen the FD mounting bolt, just enough so that the FD clamp can be hand-rotated.

Hold the front derailleur cage with one hand to rotate and hold it in place. The other hand can be used to loosen and tighten the mounting bolt.

Set the gap between the bottom of the FD cage plate and the top of the biggest chainring to 1-1.5mm.

Set the FD angle such that the FD outside cage is parallel to the Biggest Chainring.

Tighten the FD mounting bolt, then pull the FD cage by hand towards the biggest chainring to check the FD height and angle.

Repeat the process of loosening the clamp, adjusting, then tightening the clamp until the height and angle of the FD are correct.

Step 2: Set Low Gear Limit Screw

Make sure the chain is in the smallest chainring in front, and the largest cog in the rear. (Lowest gear combination)

Make sure the FD shifter cable is not under tension. Loosen the FD cable anchor nut if necessary.

Locate the low gear limit screw. Most front derailleurs have an "H" and an "L" stamped next to two small screws. These are the High (H) and Low (L) gear limit screws.

If there are no markings next to the screws, you can determine which is the high and which is the low by turning one, then the other.

With the derailleur shifted to the lowest gear, when you turn the Low gear limit screw clockwise, it will move the derailleur away from the frame of the bike.

Using a small flat head screwdriver, adjust the FD Low Limit Screw to achieve a 1 - 1.5mm gap between the FD inside cage plate and the chain.

Turning the Low gear limit screw CW will move the derailleur away from the bike, and turning it CCW will move the derailleur towards the bike.

Spin the crank arm slowely to verify this spacing throughout the full length of the chain.

Step 3: Re-Anchor the FD Cable.

Make sure the FD cable anchor nut is loose and the cable is free.

Turn the FD shifter adjuster barrel fully clockwise, then unscrew it one turn.

Pull the FD cable tight with one hand, and tighten the FD cable anchor nut with the appropriate tool.

Make sure the cable is routed properly through anchor plate, and that the anchor plate is seated correctly.

Most cable anchor plates have a groove cut in them that the cable should sit in.

Shown at left: Front Derailleur Cable is resting in the groove on the cable anchor plate.

Step 4: Set High Gear Limit Screw

Shift both the front and rear derailleurs into the highest gear (biggest chainring on front, smallest gear on back).

If the front derailleur will not shift all the way to the biggest chainring, unscrew the high gear limit screw until you can shift onto the biggest chainring.

The High gear limit screw is marked with an "H" and is right next to the Low gear limit screw.

By hand, pull the FD away from the bike as far as possible. At this point, it is resting against the High gear limit screw.

If you can't pull the derraileur far enough for it to reach the limit screw you may need to release the cable.

Still holding the front derailleur at its farthest outward point, check the gap between the outside cage plate of the FD and the chain.

There should be a 1-1.5mm gap between the derailleur and the chain.

Spin the crank arms to check this gap over the whole length of the chain.

If the chain moves left and right excessively (more than 1mm), the big chainring is likely bent out of true. You will need to true the biggest chainring, and possibly the middle and smallest chainrings too, or the chain will likely rub against the derailleur cage.

Adjust the high gear limit screw such that there is a gap of 1-1.5mm between the FD outside cage and the chain when the FD is at its farthest outward point.

The High gear limit screw is marked by an "H", and it is next to the Low gear limit screw.

Step 5: Set FD Cable Tension

Shift the chain to the lowest gear (biggest cog in rear and smallest chainring in front).

While turning the crank arms, shift the front derailleur from 1st to 2nd gear (move the chain from the smallest to the middle chainring), pushing or turning the shifter mechanism past the 2nd gear indent if necessary.

If the chain will not shift from first to second gear, release the shifter and increase the cable tension by turning the barrel adjuster counter clockwise.

Re check the shift from first to second gear, shifting past 2nd gear if necessary to get the chain to shift properly.

If you have to turn the barrel adjuster more than 4 full turns out (CCW) to get the chain to shift into second gear, you will need to re-anchor the shift cable.

Shift back into the lowest gear and screw the barrel adjuster all the way in (CW). Loosen the cable anchor nut, pull the cable tight by hand, and re-tighten the cable anchor nut.

Now repeat the process of checking the shift action, and tightening the barrel adjuster until the chain shifts smoothly from first to second gear.

Now carefully watch the shift from second gear to first gear.

If the chain has a tendency to stand on top of the teeth of the chainring, or actually fall all the way off the inside of the smallest chainring, then you will need to adjust the low gear limit screw, tightening it slightly so that the derailleur cage will not move so close to the frame of the bike.

Re-check this shift (2nd-1st) and repeat the low gear limit screw adjustment if necessary.

If you cannot get the chain to shift from 2nd gear back to first, or it takes a few seconds before the chain shifts, then you will need to slightly loosen the low gear limit screw (turn CCW).

Also check to make sure that when the chain and derailleur are in first gear, that the front derailleur cable is not pulling on the front derailleur, and stopping it from moving to it's farthest inward position.

When you shift into low gear, the front derailleur should be resting against the low gear limit screw,

Shift the chain back onto the middle chainring. Check for chain rub with the rear derailleur on the lowest gear (largest cog).

If your shifter has trim gear, or an intermediate gear, try shifting back slightly to this trim gear to see if the chain rub is aleviated.

If you don't have a trim gear, or it does not get rid of the chain rub, decrease the cable tension slightly to try and get rid of this chain rub.

Re-check the shift from the smallest to the middle chainring.

If you cannot get the chain to shift up onto the middle chainring without the derailleur cage rubbing on the chain (with the chain on the low gear in the rear), then you will need to adjust the other parameters of the derailleur (height, angle etc.).
Consult an instructor about this advanced technique.

Shift the chain onto the smallest chainring, and the smallest gear on the back. If the chain rubs against the derailleur cage, you can either clear this condition with trim gear, if available, or allow it to exist because this is an undesirable gear combination due to severe chain skew.

Now shift the chain onto the middle chainring, then up onto the largest chainring.

If the chain will not shift up to the largest chainring, try pulling the derailleur all the way outward toward the high gear limit screw to make the shift.

If the chain still does not shift, or shifts very slowely, you will need to unscrew the high gear limit screw until the chain shifts easily onto the largest chainring when you pull the front derailleur all the way against the high gear limit screw (away from the frame of the bike.)

If the front derailleur pushes the chain all the way off the largest chainring, or causes it to "stand" on top of the chainring before settling onto the gear, then you will need to adjust the high gear limit screw to bring the front derailleur in slightly toward the frame of the bike.

An example of the chain pushed too far outward. The chain has essentially fallen off the Biggest Chainring. Check both the FD High Limit Screw setting and the FD angle.

Once you have gotten the chain to shift onto the largest chainring, check for chain rub with the chain on the smallest rear cog.

If necessary, increase the cable tension slightly with the barrel adjuster to clear this chain rub.

Also check to make sure that the high gear limit screw is not stopping the front derailleur from moving over farther away from the frame of the bike.

With the chain still on the largest chainring, shift to the largest rear cog, and check for chain rub in this gear combination.

If there is chain rub, you can use trim gear if available to clear this condition.

If you don't have trim gear, it is best to let this cross gear chain rub to exist, so that there is no chain rub in the high-high gear combination.

Step 6: Final Check

Repeatedly shift the front derailleur between the chainrings, watching and listening to the shifting action.

The front derailleur should now shift between the three chainrings smoothly, without throwing the chain off the high or low gear.

There should be no chain rub in the highest gear combination (big chainring/ small cog) and the lowest gear combination (small chainring/ big cog).

There should be minimal rubbing in the cross gears (big chainring/ big cog, and small chainring/ small cog).

If the front derailleur is not satisfying all of these conditions, then you most likely need to adjust one or more of the physical parameters of the derailleur (height, angle, etc.) in order to improve shifting performance.

You should consult an instructor about this advanced technique.

Once you are done adjusting the front derailleur in the work stand, test ride the bike to check the shifting action in all gear combinations and adjust if necessary.