How to adjust a front derailleur
This entry was posted on December 20, 2012.
The front derailleur is responsible for shifting between your chainrings (the forward set of gears on your bicycle). The derailleur consists of a guide or cage for your chain that can be shifted from side to side by means of a cable that follows the frame of your bike and attaches to your shifting levers.
On new bikes, these cables are fresh, and may stretch a small amount over the first several months of riding your bike. This can cause your derailleur to become slightly loose and rub against your chain, which puts wear and tear on both parts and decreases the efficiency of your pedaling.
Fortunately, adjusting your front derailleur is quite easy and only takes a basic set of tools and a few minutes. You may have to adjust the derailleur every few months if you ride a good deal, or every few years if you are a more casual rider, so it pays off to learn this simple technique. We will also explore how to adjust the height of your derailleur, which can effect the smoothness of shifting gears.
It is important to note that crossing the chain -- riding in the easiest chainring and hardest sprocket, or vice versa -- is generally a bad idea. This compromises the strength of your chain and can cause rubbing against the derailleur. If your chain is rubbing and you ride in these gears, it’s you that needs to adjust, not the derailleur!
Time required: 15 minutes
- 5mm Allen wrench (aka hex wrench)
- Small Philips-head screwdriver
- Ruler or measuring tape (optional)
Step 1: Let’s start by adjusting the height of the derailleur. Shift into the largest chainring in front. Now pull out a ruler: the forward portion of the derailleur chain guide should be between 3-5 millimeters above the teeth of the largest gear in your chainring.
Step 2: If the derailleur is too low or too high, shift into the smallest chainring of your front gears and the smallest sprocket at the back. This releases the tension on the shifting cable. If your derailleur is situated at the correct height, skip to step 6.
Step 3: Grasp the derailleur with your left hand to hold it in place. Using a 5mm allen wrench (hex wrench), loosen the bolt on the forward portion of the derailleur mount where it attached to the bike frame. Use your hands to carefully adjust the height of the derailleur. Make sure that the derailleur is not touching the teeth of the chainring, and that the chain cannot slip out from underneath the derailleur.
Step 4: Gently adjust the side-to-side angle of the derailleur, so that the outer plate of the derailleur is parallel with the chainring. The chain may be just barely touching the inner surface of the outer plate of the chain cage.
Step 5: Re-tighten the bolt to secure the derailleur mechanism in place. Try pedaling and shifting throughout your gears to see if rubbing is still occurring or if shifting is causing problems.
Step 6: To fine tune the derailleur position, let’s adjust the limiter screws on the top side of the derailleur mechanism. The upper screw keeps the chain from slipping off the inner side of the gears, and the lower screw keeps the outer side in check. Let’s start with the lower screw. First, shift into the largest chainring in the front and your smallest cog in the back. Use your screwdriver to turn the lower screw clockwise to allow slightly more room between the chain and the outer edge of the derailleur; counterclockwise will reduce this distance. Tighten it up until there is just a millimeter or two of spacing. This will keep the chain in position while not allowing rubbing.
Step 7: Last step! Shift into your smallest chainring in the front and your largest cog in back. Turn the upper limiter screw clockwise to move the derailleur slightly outward, reducing the space between the inner plate of the chain cage and the chain itself. If you need more space, turn the upper screw counterclockwise. This is the mirror image of step 6, so make sure there is just enough space between the chain and the inner edge of the derailleur.
Step 8: Take a test ride! If you followed these directions carefully, you should be shifting smoothly and leaving those annoying metal-on-metal rubbing sounds behind. If you are still experiencing rubbing, use these instructions to adjust your derailleur further as necessary.