4. Ensure that your rear derailleur inner limit screw prevents the derailleur from contacting the spokes.
The low-gear limit screw stops the inward movement of the rear derailleur, preventing it from going into the spokes; it's often labeled "L" and is usually the bottom screw.
- Shift the chain to the inner chainring on the front. Shift the rear derailleur to the largest cog gently, in case the limit screw does not stop the derailleur from moving into the spokes.
- If the derailleur touches the spokes or pushes the chain over the largest cog, tighten the low-gear limit screw until the derailleur does neither.
- If the derailleur cannot bring the chain onto the largest cog, loosen the screw one-quarter turn. Repeat this step until the chain shifts easily up to the largest cog but does not touch the spokes or push the chain over the top of the cog.
5. Adjust your left shift cable's tension so that your front derailleur works optimally.
- With the chain on the inner chainring, remove any excess cable slack by turning the barrel adjuster on the cable stop counterclockwise (or loosen the cable-fixing bolt, pull the cable tight with pliers, and tighten the bolt).
- Check that the cable is loose enough to allow the chain to shift smoothly and repeatedly to the inner chainring.
- Check that the cable is tight enough that the derailleur starts to move as soon as you move the shifter. Fine-tune while riding.
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Illustrations by Todd Telander, courtesy of VeloNews.