Gear Indexing & Adjustment
Skipping gears, chain falling off, or noisy shifting? Usually just cable tension. The barrel adjuster on your rear derailleur is the magic dial — quarter turns solve most problems. (Fixie riders: skip this one, you've transcended gears.)
Park Tool's definitive guide. Systematic and thorough.
If shifting to larger cogs is sluggish (harder to go up), the cable is too loose — turn barrel adjuster anti-clockwise.
If shifting to smaller cogs is sluggish (harder to come down), the cable is too tight — turn barrel adjuster clockwise.
Limit screws (H and L on the derailleur) prevent the chain falling off the top or bottom of the cassette. Only touch these if the chain is actually dropping off.
New cables stretch in the first 100 miles. Expect to re-index after your first few rides with new cables.
Put bike in a work stand or flip it upside down (protect the saddle)
Shift to the smallest rear cog. Pedal and check the chain runs quietly
If it's noisy or trying to shift up, the cable is too tight — turn barrel adjuster clockwise ¼ turn
Shift up one gear at a time through the full range. Each shift should be crisp and immediate
If upshifts are sluggish: barrel adjuster anti-clockwise ¼ turn
If downshifts are sluggish: barrel adjuster clockwise ¼ turn
Repeat until all shifts are clean in both directions
LIMIT SCREWS: Only if chain falls off — H screw limits outward movement, L screw limits inward
Check the derailleur hanger isn't bent (look at it from behind — it should be vertical)
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