How to Adjust Rear Derailleur

Bike maintenance has gotten complicated with all the conflicting advice flying around. As someone who’s been wrenching on bikes for over a decade, I learned everything there is to know about rear derailleur adjustments. Today, I will share it all with you.

Tools Needed

Before we dive in, let’s talk about what you’ll actually need. I’ve done this with a bare-bones toolkit, and honestly, you don’t need anything fancy:

• Bicycle stand (optional, but makes life easier)
• Phillips screwdriver
• 5mm Allen wrench
• Needle-nose pliers
• Bike chain lubricant

Preparation

First things first – get your bike in a position where you can actually work on it. Place it on a stable surface or use a bike stand if you have one. The rear wheel needs to be off the ground so you can spin it freely while making adjustments. Take a minute to check your drivetrain components for any obvious wear and tear. If something looks really worn, replace it before you start tweaking things.

Check your Derailleur Hanger

Probably should have led with this section, honestly. A bent derailleur hanger will make all your adjustments pointless. Use an alignment tool to check if it’s straight, or if you don’t have one, take it to a bike shop. That’s what makes a properly aligned hanger endearing to us bike mechanics – it’s the foundation for everything else to work correctly.

Set High and Low Limit Screws

These screws are your safety net. They prevent your chain from derailing into your spokes or falling off completely. Look for the screws marked H (high gear) and L (low gear) on your derailleur body.

Adjust the High Limit Screw

Here’s what you do for the high limit:

1. Shift your chain to the smallest cog
2. Find that H screw on the derailleur body
3. Turn it slowly until the jockey wheel lines up perfectly with the smallest cog

Adjust the Low Limit Screw

And for the low limit:

1. Shift your chain to the largest cog
2. Find the L screw on the derailleur body
3. Turn it until the jockey wheel aligns perfectly with that largest cog

Adjust Cable Tension

This is where most people get tripped up. Cable tension is what determines how responsive your shifts feel. If it’s too loose, you’ll struggle to shift up. Too tight, and you won’t be able to shift down smoothly.

1. Start by shifting to the smallest cog
2. Use the barrel adjuster to fine-tune things – clockwise loosens, counterclockwise tightens
3. Shift through the gears and feel how they respond. Keep adjusting until the shifts are crisp and precise

Indexing Adjustment

Indexing is what makes your shifter click into each gear cleanly. When it’s dialed in right, each click moves the chain exactly one cog. No more, no less.

1. Shift to the second smallest cog
2. Use the barrel adjuster to make sure the derailleur moves the chain smoothly with each shifter click
3. Test by running through all the gears, both up and down
4. Make small adjustments until it feels perfect

B-Tension Adjustment

This screw controls how close the derailleur sits to your cassette. Get it wrong, and the upper pulley can smack into your larger cogs when you shift.

1. Find the B-tension screw (usually at the top of the derailleur)
2. Shift to your largest cog
3. Adjust the screw until there’s about 5-6mm of clearance between the upper jockey wheel and the cog

Inspect and Lubricate the Chain

A gunked-up chain will sabotage even the best derailleur adjustment. Take a few minutes to clean and lube it properly.

1. Clean the chain with a degreaser – get all that black grime off
2. Apply lubricant evenly across all the chain links
3. Wipe off the excess with a clean cloth (you want lube inside the links, not on the outside)

Final Checks

Now for the real test – take your bike for a spin. Shift through all the gears under load and listen for any weird noises or hesitation. If something still feels off, come back and make small tweaks until it’s dialed in. Keep your drivetrain clean and well-maintained, and these adjustments will hold for a good long while.