The front derailleur is the metal "cage" attached or clamped to your seat post that moves your chain from one chain ring to another. It moves from side to side, carrying the chain along with it as you click the appropriate shift lever.
You should check, clean and lube your front derailleur regularly to make sure it functions. You should check your front derailleur quickly before each ride.
The easiest way to check your front derailleur is with your rear wheel off the ground.
- Whilst in this position rotate the pedals and shift your front gear lever through its full range. If your front derailleur is properly adjusted, the chain will shift quickly and easily from one ring to the next and without overshooting or jumping off the chain set.
Got a problem? Get the answer
Front derailleur problems involve slow or inaccurate shifting. A front derailleur usually malfunctions because:
1. It's dirty and needs lubricating
2. The cable is damaged or incorrectly tensioned
3. The mechanism is not positioned properly on the seat tube
4. The limit screws are not adjusted correctly
See the navigation grid above for specific information regarding how to effectively overcome these difficulties.
If, despite the adjustments described, shifting difficulties persist, you may have a more serious shifting problem. An experienced cycle mechanic should be brought in to help.
Problems caused by dirt
Many front derailleur problems are caused by simple dirt, grit or insufficient lubrication. Even small amounts of dirt and grit can cause problems, so keep it clean and re-lubricate every month or so, depending on riding conditions.
Clean the derailleur by brushing all exposed parts with a stiff brush. Stubborn dirt is best removed by wiping with a clean rag soaked in degreaser. Be sure to clean the derailleur mechanism thoroughly but carefully, including the hard to reach areas of the main body and arm.
When re-lubing, focus on the moving pivots of the mechanism. It is best to use a spray lubricant designed specifically for bikes and, whilst lubing, shift the derailleur back and forth while spraying so you can work the lube into the tough to reach places. Wipe off excess lubricant, this will only attract dirt.
Problems caused by cable damage or incorrect tension
If a cable is very obviously damaged, it must be changed. Better to do it now, than have it "snap" whilst out on the trail. Luckily most problems with cables only require minor adjustment.
Most modern bikes have fine-tuning devices called barrel adjusters. These simple, round adjustment knobs, are usually built into derailleur systems and are typically located on your gear lever. These adjusters allow you to fine tune your derailleur by increasing or decreasing the tension of your cable.
Most bikes with "indexed" derailleur systems have barrel adjusters but not all. Plus, this method of adjustment is used more for fine adjustment of the rear derailleur than the front.
To fine-tune your front derailleur using your barrel adjuster, start with your chain on the largest front ring and largest rear cog.
- Shift your chain down to the next smallest chain ring and check to see how close the inside surface of the chain is to the inside wall of the derailleur cage.
- The two surfaces should be as close as possible (approx. 0.5mm) without touching.
- Turn the barrel adjuster counterclockwise to move the derailleur cage inward i.e. away from the chain surface. Turn it clockwise to move the cage outward.
Repositioning the front derailleur
To check the position of your front derailleur:
- Shift it so that the derailleur arm is positioned over the largest chain ring.
- The "cage", the curved section of the derailleur that the chain passes through, should be approximately 2mm above the teeth of the chain ring.
- The outer plate of the cage should be lined up parallel with the chain ring.
To reposition your front derailleur:
- Loosen the mounting bolt that holds it onto your frame.
- Re-position the derailleur by sliding it up and down and/or rotating it slightly from side to side. You may have to loosen the derailleur cable in order to move the body.
- When properly re-positioned be sure to retighten the mounting bolt carefully before riding.
Poorly adjusted limit screws cause many shifting problems. To be at it's most effective the cage must move from side to side within a very specific tolerances.
Limit screws control the inner and outer limits of your arm's sideways movement. These small screws are typically located next to one another on the main derailleur body.
Each screw controls one extreme of the derailleur movement. The "outer stop" screw determines the farthest distance the derailleur will travel away from the frame. The "inner stop" screw determines how close the derailleur will travel inwards toward the frame. Tuning these 2 limit screws correctly will ensure your derailleur performs without problems.
Which is which? Inner and outer limit screws are identified by many methods. Most are labeled with "L" for low gear, which refers to the smallest chain ring, or "H" for high gear, which refers to the largest.
Setting the inner stop.
The first step is to see how far the derailleur swings in toward your frame. To do this, you must shift the derailleur to the innermost chain ring and let the tension out of the cable by loosening the bolt that anchors the cable to the body. Loosening this cable will ensure that the arm is free to swing freely.
Then shift your chain to the smallest chain ring and the largest rear cog. Use your inner limit screw to position the inner wall of the cage so that there is 2mm of clearance at their closest point.
Once you've set your inner stop, with your chain still on the smallest chain ring, pull the cable taut and re-connect and tighten.
Setting the outer stop
Now shift your chain to the largest chain ring and the smallest rear cog. Use your outer limit screw to position the outside face of the cage 2mm away from the outer surface of your chain at their closest point.
It is this adjustment that stops your chain from overshooting the outermost chain ring and falling off your bike. Since some shifting systems do not automatically shift the derailleur as far as it can, pull outward slightly on the front derailleur cable as you set and test your outer limit adjustments. This added cable tension will ensure that the chain can't be thrown.