Things You'll Need:
- Bike stand Metric hex keys screwdriver pliers or a "third hand" tool
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Step 1
Derailleur height and angle is usually controlled by the same screw that secures the derailleur to the frame. By loosening that screw the derailleur can be moved up and down, or twist left and right. Set the height of the derailleur so that it is no more than two millimeters above the largest chain ring (the gear that the chain goes around). The closer the better, but make sure the derailleur cage (the thing that rubs the chain) doesn't touch the chain rings at any point. Also, adjust the derailleur so the cage is parallel to the chain rings.
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Step 2
Next move to the low limit, one of two screws on the top or side of the derailleur that adjusts how far the cage can move to the right and left when there is little to no tension on the cable. It is best to do this with the cable removed completely. With the rear derailleur in the largest (easiest) gear and the front derailleur in the smallest chain ring, screw the low limit clockwise to move the cage to the right and counter clockwise to move it to the left. Adjust it so there is between one and three millimeters distance between the inside of the cage and the chain, with absolutely no rub.
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Step 3
Before working on cable tension, the cable must be pre-stretched, especially if the cable is new. Do this by firmly clamping the cable to the derailleur, then pull down with your hand. If you have soft skin use a tool for grip, but don't use too much leverage or you'll break the plastic cable housing.
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Step 4
Now work on the cable tension by loosening the clamping bolt with the shifter in first gear. Pull the cable tight and clamp it down -usually the cable can be pulled without tools but sometimes it helps to use pliers or a "third hand" tool.
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Step 5
If you have a triple chain ring system, shift to the second chain ring, as indicated by your shifter. If the cable is properly tensioned the chain should not rub on the cage when the rear derailleur is in its smallest (hardest) and largest (easiest) gears. Sometimes the cage rubs in both smallest and largest rear gears, in which case use the second smallest and largest gears as a guide. If the chain rubs when the rear is in the smallest gear, add tension; if the chain rubs when the rear is in the largest gear, reduce tension. Use the barrel adjuster, a turn-grip usually found where the cable meets the shifter, to do fine adjustments.
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Step 6
If you have a double chain ring the shifter should give you two positions, or an extra click, before shifting to the large ring. The cable is set correctly when you get no rub from the small rear gear after the second click. If not, add tension.
You should also get at least two settings in the big ring and when adjusted properly it can avoid rub in every gear. If it rubs in the easy gears reduce tension.
In the event that you get chain rub when in the biggest front and rear gears AND the smallest front and rear gear, don't worry about it and move on. The manufacturers don't want you cross-chaining like that anyway. -
Step 7
The last thing to adjust is the high limit. Do this in the largest chain ring and the smallest rear gear. The high limit screw works the same way as the low limit screw, and the goal is to get the cage as close to the chain as possible without touching it. Spin the cranks a few times to make sure there is no touch at any point.
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Step 1
Test first in the stand by making sure the shifting is quick and without skips in all chain rings with the rear derailleur on the largest and smallest gears.
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Step 2
Test on the road, sidewalk, or parking lot using all gearing combinations. You may notice different results when you have some weight on the pedals.
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Step 3
Have a knowledgeable friend or bike mechanic check your work over to make sure you didn't forget anything.
