How to Adjust a Bicycle Derailleur: Step-by-Step Rear Derailleur Tuning

Most shifting problems come down to two things: cable tension and limit screws. With a few minutes and a screwdriver you can fix them yourself.

What you’ll need

• A Phillips screwdriver
• A hex key (usually 5 mm) for the cable clamp
• A way to lift the rear wheel. A bike repair stand makes this much easier.

Before you start

• Clean and lube the chain.
• Check that the wheel is seated straight in the dropouts.
• Look at the derailleur hanger from behind. If it’s bent, no adjustment will fix shifting; it needs straightening or replacing.

Step 1: Set the limit screws

The “H” and “L” screws stop the derailleur from moving too far.

1. Shift to the smallest cog. Turn the H screw until the upper pulley lines up directly under that cog.
2. Shift to the largest cog, pushing gently on the derailleur. Turn the L screw so the chain can reach the largest cog but can’t go into the spokes.

Step 2: Set cable tension

1. Shift to the smallest cog.
2. If the cable is slack, loosen the clamp bolt, pull the cable snug by hand and retighten.
3. Shift up one cog at a time. If it’s slow to climb to a larger cog, turn the barrel adjuster counterclockwise (adds tension).
4. If it’s slow to drop to a smaller cog, turn it clockwise (reduces tension).
5. Use quarter-turns and test after each.

Step 3: Test ride

Shift through all gears under light pedaling. Fine-tune with the barrel adjuster while riding.

Common problems

• Skipping under load: often a worn chain or cassette, not adjustment.
• Noisy in the middle gears: small tension tweak.
• Won’t hold adjustment: cable stretch on new cables (normal), or dirty housing.

Tools worth having

A multi-tool handles most roadside tweaks. For regular home maintenance, a stand like the Feedback Sports Sprint holds the bike at working height.

When to see a shop

Bent hangers, electronic shifting and worn drivetrains are often best left to a mechanic. Regular checks also help prevent flats; see our flat prevention tips.

Understanding how a rear derailleur works

The rear derailleur moves the chain across the cassette when the shifter pulls or releases the cable. Three things control where it ends up:

• Cable tension sets how far each click moves it.
• Limit screws set the outer stops so the chain can’t fall off either end.
• The B-tension screw sets the gap between the upper pulley and the cogs.

If one is off, shifting suffers. That’s why it helps to adjust them in order: limits, then cable tension, then B-tension.

Step 4: Set the B-tension

1. Shift to the largest cog (or the smallest, depending on the brand’s instructions).
2. Look at the gap between the upper pulley and the cog. Most manufacturers recommend about 5 to 6 mm.
3. Turn the B-tension screw in to increase the gap or out to reduce it.
4. Too small a gap causes a rough, noisy sound; too large makes shifting slow.

Checking the derailleur hanger

A bent hanger is one of the most common causes of shifting that won’t adjust. Signs include:

• The derailleur looks tilted when viewed from behind.
• Shifting works well in some gears and badly in others.
• The chain jumps after a crash or after the bike fell on its drive side.

A bike shop can straighten a hanger with an alignment tool in a few minutes. Replacement hangers are specific to each frame, so keep a spare if you ride a lot.

Cable and housing care

• Replace cables and housing when shifting feels gritty or slow, often once a year for regular riders.
• New cables stretch slightly, so expect to fine-tune after a few rides.
• Keep the housing ends cut cleanly and capped with ferrules.

Front derailleur basics

The front derailleur uses the same ideas:

1. Set the height so the outer cage clears the big chainring by 1 to 3 mm.
2. Align the cage parallel to the chainrings.
3. Set the low and high limit screws so the chain doesn’t drop off either side.
4. Adjust cable tension with the barrel adjuster or inline adjuster.

Maintenance that keeps shifting crisp

• Clean the chain and cassette regularly.
• Lube the chain lightly and wipe off the excess.
• Check chain wear with a chain checker. Replace a worn chain before it wears out the cassette.
• Keep jockey wheels clean; grit builds up fast.

A repair stand helps for all of these jobs, since you can spin the pedals and watch the drivetrain at eye level.

Troubleshooting chart

• Chain won’t go to the largest cog: L limit too tight, or cable too loose.
• Chain drops into the spokes: L limit too loose. Fix immediately.
• Chain won’t go to the smallest cog: H limit too tight, or cable too tight.
• Rattling in one gear: small cable-tension adjustment.
• Ghost shifting: worn chain or cassette, a bent hanger or dirty cables.

Quick roadside fix

If shifting goes wrong mid-ride, turn the barrel adjuster a quarter turn at a time while pedaling gently on a quiet stretch. Counterclockwise helps when the chain won’t climb to larger cogs, and clockwise helps when it won’t drop to smaller ones. Save bigger adjustments for home.

Frequently asked questions

How often should I adjust my derailleur?

Only when shifting gets noisy, slow or skips. New bikes and new cables usually need a small tweak after the first few weeks.

Do I need special tools?

A screwdriver and hex keys are enough for most adjustments. A repair stand makes the job easier, and a chain checker helps with maintenance.

Why does my bike shift badly after a crash?

The hanger may be bent. Have it checked before adjusting anything else.

When should I take it to a shop?

For bent hangers, electronic shifting, worn drivetrains or if adjustments don’t help.

A video from Park Tool showing how to set the limit screws and indexing on a rear derailleur.

Top image: “Derailleur and bike chain” by Alextredz (resized and cropped), CC BY-SA 4.0, via Wikimedia Commons.