Derailleur setup & indexing
Crisp, silent shifts — every gear, every time.
Skipping, hesitating or noisy gears usually just need indexing. Set the high/low limits, dial the B-tension, tension the cable (or micro-adjust electronic), then fine-tune the barrel adjuster until every shift is instant.
Shimano
Mechanical + Di2. Di2 sets limits mechanically then micro-adjusts electronically in E-TUBE.
Torque specs
| RD mounting bolt | 8–10 N·m |
|---|---|
| Cable fixing bolt | 6–7 N·m |
| Shifter clamp | 6–8 N·m |
Manufacturer-claimed — always confirm against your model manual.
Video walk-throughs
Shimano rear derailleur indexing (limits + B-tension)
Park Tool
Di2 adjustment in E-TUBE
GCN Tech
Opens a YouTube search — we link out rather than embed unverified videos.
Manuals & documents
Further reading
Mechanic's tips
- Set H and L limits with the barrel adjuster fully in.
- Di2 still needs the mechanical limits set first.
Tools you'll need
2 / 2.5 / 4 / 5 mm hex keys
Limits, clamp, mount
Cable cutter
Mechanical only
Small screwdriver
H / L limit screws
Hanger alignment gauge
The #1 hidden cause of bad shifting
Repair stand
Pedal & shift freely
Step by step
- 1
Check hanger alignment
A bent hanger defeats every other adjustment — gauge it first.
- 2
Set the H limit
Stops the chain overshooting into the smallest cog / off the cassette.
- 3
Set the L limit
Stops the chain diving past the biggest cog into the spokes.
- 4
Set B-tension
Guide-pulley-to-cog gap for clean shifts across the range.
- 5
Tension the cable
Mechanical: pull cable taut in the smallest cog. Electronic: skip.
- 6
Index
Barrel adjuster (mech) or micro-adjust in the app (Di2 / AXS).
- 7
Fine-tune under load
Shift up and down while pedalling; nudge until instant.
- 8
Check cross-chain
Confirm no rub in the extreme gears.
Frequently asked
Why do my gears only skip when I pedal hard? +
That is a cable-tension symptom, not a broken part: under load the derailleur needs slightly more pull to sit dead-centre on each cog. Add a quarter-turn of tension at the barrel adjuster (or shifter, for older Shimano) and re-check across the whole cassette.
Is a hanger alignment gauge really necessary for a home tune? +
Yes — a bent hanger is the single most common cause of gears that will not index cleanly no matter how carefully you set limits and cable tension. A basic gauge is inexpensive and takes the guesswork out before you touch anything else.
Do electronic derailleurs (Di2 / AXS) still need this whole process? +
The mechanical side — hanger alignment, H/L limits and B-tension — is identical. Only the fine indexing step changes: instead of a barrel adjuster you use micro-adjust buttons in the E-TUBE or AXS app, in half-click increments.
How often should I actually re-index? +
Budget a check every 2 500 km or 12 months, and always after fitting a new cable, chain, cassette or derailleur hanger — cable stretch and bedding-in are the usual culprits for drift between services.
How we source this
- Steps and standards are drawn from the official Shimano, SRAM and Campagnolo dealer/service manuals plus Park Tool's public repair library — the same references a shop mechanic would use.
- Torque values are manufacturer-claimed specifications, not independently measured by BikeBuy — always confirm the figure stamped on your specific derailleur, mount and frame against its model manual before applying a torque wrench.
- Video links point to the manufacturer's own channel or a Park Tool search result; BikeBuy never fabricates a YouTube video ID or embeds an unverified upload.
- This is a general field guide for typical current mechanical and electronic setups — cross-check details for older, long-cage or non-UDH-hanger drivetrains against your specific model manual.