How To Adjust A Bike Derailleur

What is a derailleur?

A bike has two derailleurs, one in the front and one in the back. A derailleur is responsible for moving the chain out and up, which allows the bike to shift to different cogs (and gears, respectively). All cycles have one, even folding bikes!

How does it work?

The rear derailleur on a bike makes it possible for a bike to shift gears by pushing the chain from one cog onto another. The front derailleur on a bike shifts between gears by moving the bike chain from ring to ring on the crankset. All derailleurs feature a spring that is responsible for keeping the chain moving in one direction. Most of the force behind this piece of machinery is provided by the person riding the bike.

Why is it needed?

The derailleur is an essential bike part for smooth shifting with minimal rider effort. Failure to adjust the derailleur properly could cause the chain to slip off and damage the bike’s frame.

How do I adjust it?

Here are a few signs that you should adjust your derailleur:

• If you push or click the shifter and the chain doesn’t quite catch
• If you feel a hesitation when you shift into a harder gear
• If you hear a clicking sound when you’re on the largest cog

Are you experiencing one of these issues? Then it’s time to adjust your derailleur!

1. Ensure your derailleur is at the proper height. If the cage is too high, it may cause your bike to shift incorrectly or in a poor manner. If the cage is too low, it is likely to catch on the gears. The gap between the teeth on the front gear and the bottom of the cage should be only about as wide as a penny’s length. In order to raise or lower the derailleur, shift to the lowest gear. This relieves cable tension. Loosen the clamp bolt on the derailleur and shift it wither up or down depending upon which way you need to adjust the height. Retighten the bolt and shift back to middle gear.
2. Is your derailleur at the proper angle? The derailleur cage should be almost parallel to the chain. If it too far in one direction or the other, it may case poor shifting. Shift to the lowest gear and view the chain from directly above it. Is it parallel to the cage? If it needs to be rotated in either direction, loosen the clamp and rotate the derailleur to the correct angle. Shift back to a higher gear and observe the chain. If it is parallel, your work is finished! If not, keep adjusting until the alignment is correct.
3. Put the bike into the lowest gear possible (closest to the spokes)
4. Look at the rear sprockets and make sure they’re not touching the cog. You’ll know if this happens while riding, because it will make a loud noise when the bike is trying to shift into the lowest gear.
5. If the cogs are touching the cassette (where the chain connects to), turn the derailleur alignment screw clockwise. This should increase tension so the cogs shift away from the cassette. If the cogs are too far away from the cassette, you need to loosen the screw until the cog and cassette touch and then tighten slightly.
6. Is the lower cable tense? Good, now shift to the highest gear. Look at how the chain moves along the smallest of the cogs.
7. If it looks like it might come off of your bike’s axle, get out your wrench and tighten the “H” screw. If the chain looks like it’s rubbing onto the next gear, loosen it. Watch the derailleur as you tighten or loosen the screw. It should move just a tiny bit. When you’re finished, readjust the cable until the gear shifting is smooth.
8. Now, shift into the lowest gear and make sure the chain does not fall off when doing so. Does the chain look like it is leaning toward the spokes? If so, tighten the “L” screw. If your bike seems like it wants to shift downwards, loosen the “L” screw. Always test the adjustments you have made, and if needed perform steps 5 and 6 again.
9. At this point, you have shifted into both the highest and lowest gear and adjusted both the “H” and “L” screws. To ensure they screws are in the correct place, try to shift through all the gears in both directions so you can tell if your bike is now shifting properly. If the bike is having troubling when you try to shift down or the chain is very close to the smaller cogs, tighten the cable by moving the tension screw counterclockwise (to tighten it) until the shifting is correct. Likewise, if the bike is not shifting up very well or the chain sticks to the larger cogs, loosen the cable by adjusting the tension screw clockwise (to loosen it).
10. Look at the rear derailleur. Is it out of shape or bent in any way? It shouldn’t be! If it bents in toward the spokes, it is definitely bent and could cause issues when you’re riding. Look at the rear derailleur from behind. There should be no sideways slant. The two pulleys in the back of the bike should line up exactly underneath one another. Check to make sure these pulleys and their tension lines are lined up with the sprockets that are above them. If they do not line up, do not try to pull the derailleur into the proper place. This often causes the cage to bend. Instead, remove the rear derailleur to straighten it out. Some bike shops have special tools for this. If you’re not near a bike shop, you can perform a rough adjustment with an adjustable wrench.
11. Check your chain length. A chain that is too short can jam often and possibly ruining the rear derailleur. If it is too long, it will have slack in some gear combinations.
12. Lubricate the chain, the pivot points, and all of the screws on the bike. Stiff chain links can detrimentally affect how well the bike shifts.