Front Derailleur Adjustment — Height, Limits & Cable

Drivetrain · Beginner–Intermediate · ~15 min read · 8 steps

Drivetrain

Front Derailleur Adjustment

Front derailleurs are mechanical devices of surprising sensitivity — a cage that's 1mm too high or rotated a few degrees out of alignment will cause chain rub, poor shifting, or both. The good news is they follow a strict setup sequence that makes the process reliable once you understand what each adjustment actually does.

How a Front Derailleur Works

A front derailleur is a cage that pushes the chain sideways onto a different chainring. Unlike the rear derailleur, which moves constantly under indexing, the front derailleur only moves to two or three positions (matching your chainring count). It has no indexing spring per se — the cable pulls it out, and a return spring pulls it back in. This means cable tension and physical cage position are the entire mechanism. There is no barrel adjuster on most front derailleurs; you set tension at the cable anchor bolt.

Three separate adjustments must be correct before the front derailleur can work well, and they must be set in order:

Cage height and angle — physical derailleur position on the seat tube
Limit screws (L and H) — how far inward and outward the cage can travel
Cable tension — how strongly the cable pulls the cage outward

If the front derailleur is freshly installed or has been moved, you must go back to step 1. Adjusting cable tension on a mispositioned derailleur wastes time — the position defines everything downstream.

Step 1 — Set Height and Angle

Set cage height: 1–3mm clearance above chainring

Loosen the clamp band (or braze-on bolt) just enough to allow the derailleur to rotate on the seat tube. Shift to the large chainring. Look down from above: the outer plate of the cage should sit 1–3mm above the tallest point of the large chainring teeth. Too high and the chain won't shift cleanly. Too low and the cage will contact the chainring. 2mm is the ideal for most setups.

Set cage angle: parallel to the chainring

While the clamp is still slightly loose, rotate the derailleur body until the outer cage plate is perfectly parallel to the chainring — viewed from above, the outer and inner cage plates should describe an arc that matches the curve of the chainring. Most chainrings are 110 or 130mm BCD and very similar in curvature. A front derailleur that's rotated inward at the front will rub on the downshift; rotated outward at the front will rub on upshifts. Tighten the clamp to 5–6 Nm.

Step 2 — Set the Limit Screws

The L (low/inner) limit stops the cage from pushing the chain inward off the small chainring. The H (high/outer) limit stops it pushing the chain outward off the large chainring. Unlike the rear derailleur, front limit screws are physical hard stops — setting them correctly protects against dropped chains.

Set the L limit (small chainring, inner stop)

Shift to the small chainring and the largest rear sprocket (lowest gear combination). Disconnect or fully slacken the cable — with no cable tension, the derailleur should sit at its innermost position. The inner cage plate should clear the chain by 0.5–1mm — close enough to guide but not rubbing. Turn the L screw clockwise to push the cage outward (more clearance), counter-clockwise to allow more inward travel. With L set correctly and no cable, the chain should run on the small ring without touching the cage.

Set the H limit (large chainring, outer stop)

Shift to the large chainring and smallest rear sprocket (highest gear combination). Pull the cable to full tension and hold it or temporarily clamp it. The outer cage plate should clear the chain by 0.5–1mm on the outside. Turn the H screw clockwise to pull the cage slightly inward (less clearance), counter-clockwise to push it further outward. If H is too tight, the derailleur can't reach the large ring. If too loose, the chain can throw off the outer edge on hard pedal strokes.

A dropped chain on the outer side of the large chainring can jam in the frame/chainring gap and damage the frame. Set the H limit conservatively — err on the side of slightly too tight, then loosen by quarter-turns until shifting works cleanly.

Step 3 — Set Cable Tension

Set tension with the chain on the small ring

With the chain on the small chainring and limits correctly set, route the cable through the anchor bolt clamp. Pull it taut with your fingers — firm but not forceful — and tighten the anchor bolt to 5–6 Nm. Now shift to the large ring: the derailleur should move the chain cleanly in one click. If it hesitates or won't reach the large ring, the cable tension is too low — add tension by re-routing with the cable pulled more firmly, or if your shifter has an inline barrel adjuster, turn it counter-clockwise.

Test downshift and trim

Shift back to the small ring: the cage should pull fully inward cleanly. If it won't return fully (chain rubs on inner cage in small ring), cable tension is too high. If it returns but sluggishly, consider checking cable friction or housing condition.

Understanding Trim Positions

Modern Shimano STI and SRAM DoubleTap shifters have "trim" — a half-click position that slightly adjusts the front derailleur cage inward or outward without actually changing chainring. This compensates for chain angle when using cross-gear combinations:

Large chainring + large sprocket (cross-chain, not recommended but common): use the trim inward position to prevent chain rub on the inner cage plate.
Small chainring + small sprocket (also cross-chain): use the trim outward position if the chain rubs the outer cage plate.

Trim is activated by a partial lever movement before the full click. On Shimano STI, a small movement of the brake/shift lever without a full shift click activates trim. If chain rub in cross-gear combinations persists even with trim engaged, the derailleur position or cable tension needs adjustment.

Persistent Chain Rub Troubleshooting

Rubs on inner cage in large ring: H limit too tight or cable tension too high — loosen H screw by quarter-turns, or reduce cable tension slightly.
Rubs on outer cage in small ring: L limit too tight — loosen L screw. Or cable tension too high.
Rubs only in cross-chain gears: This is normal chain angle physics. Use trim, or avoid extreme cross-chaining by changing gear combinations.
Cage contacts chainring on shift: Cage too low — re-check height (minimum 1mm above largest ring tooth).
Slow or missed shifts on upshift: Cable tension too low, or cable housing kinked/frayed. Check housing condition before adding tension.

1× drivetrains (a single chainring with a wide-range cassette, common on modern MTB and gravel bikes) have no front derailleur at all — this guide applies only to 2× and 3× setups.