Having a properly adjusted rear derailleur, such as knowing how to adjust rear derailleur on a mountain bike, is essential for optimal shifting performance on your mountain bike. A derailleur that is out of adjustment can cause issues like the chain slipping gears, making excessive noise, getting stuck between cogs, or even derailing completely.
Thankfully, adjusting a rear derailleur is a straightforward process that most mountain bikers can tackle themselves with some basic tools and mechanical know-how.
When to Adjust Your Rear Derailleur
Here are some signs that indicate it’s time to adjust your rear derailleur:
- When the Chain is slow to shift gears or skip gears entirely.
- When the Chain rubs on the derailleur cage or makes excessive noise when pedaling.
- When You experience “ghost” shifting where the gears seem to change on their own.
- When the Chain falls off the derailleur pulley wheels into the frame.
- When Gears don’t reach the smallest or largest rear cog.
If you notice any of these issues, it’s likely time to dial in your derailleur adjustments. Doing so can dramatically improve shifting performance.
Rear Derailleur Components You Should Know Of
Before jumping into the adjustment process, it helps to understand the components that make up a rear derailleur:
- Cage – Holds the jockey wheels and moves the chain between gears.
- Jockey Wheels – Guide the chain between rear cassette cogs.
- Tension Spring – Provides constant downward tension to take up chain slack.
- Limit Screws – Control how far the cage can move inboard or outboard.
- B-Tension Screw – Adjusts how close the top jockey wheel sits to the cassette cogs.
- Barrel Adjuster – Fine tunes the cable tension.
Knowing the function of each component will help you accurately diagnose issues and make proper adjustments.
Adjusting a rear derailleur doesn’t require many specialty tools. Here is what you’ll need to have on hand:
- 4mm & 5mm hex wrenches
- Phillips head screwdriver
- Cable cutters
You may also find the following helpful, though not mandatory:
- Bicycle work stand
- Rear derailleur hanger alignment tool
- Chain wear gauge
Step-by-Step Adjustment Instructions
Now let’s walk through the full rear derailleur adjustment process from start to finish:
Step 1: Check Hanger Alignment
Before adjusting the derailleur itself, inspect your rear derailleur hanger to make sure it is properly aligned. The hanger is the tab that the derailleur mounts to on the frame. If the hanger is bent from a crash or impact, it can prevent accurate derailleur adjustments. Use a hanger alignment tool to realign if needed.
A properly aligned hanger ensures the derailleur cage sits parallel to the cassette.
Step 2: Clean & Lubricate
Cleaning and lubricating the drivetrain first will allow for smooth adjustments. Using a rag, wipe down the rear cassette, chain, and derailleur body to remove any dirt and debris. Then apply a lubricant like Tri-Flow to keep things running smoothly.
Step 3: Adjust Limit Screws
The limit screws control how far inboard and outboard the derailleur cage can shift. Start by shifting to the smallest rear cog and adjusting the inner limit screw so the chain runs centered without rubbing. Then shift to the largest cog and adjust the outer limit screw accordingly.
Step 4: Set Low Gear Adjustment
Shift to the smallest rear cog. Then use the cable tension barrel adjuster to remove any slack in the cable until the chain runs quiet and doesn’t hesitate when shifting between the smallest two cogs.
Step 5: Set High Gear Adjustment
Upshift through the gears until you reach the largest rear cog. Then use the B-tension screw at the rear of the derailleur to adjust the spacing between the top jockey wheel and cassette. There should be just enough room so the chain doesn’t get jammed between.
Aim for a 5-6mm gap between the jockey wheel and largest cog.
Step 6: Check Middle Gears
Now shift through every gear to make sure it changes smoothly without hesitation. Make fine adjustments to the barrel adjuster and B-tension screw until shifting performance is crisp and precise.
Step 7: Replace Cable (If Needed)
If adjustments don’t solve shifting issues, the shifter cable and housing may need replacement. Shift to the smallest cog, undo the cable anchor bolt, and pull out the old cable. Run the new cable through the shifter, housing, and derailleur according to the manufacturer’s instructions.
Use fresh shifter cable grease when installing the new cable for smooth running.
Step 8: Test Ride
Take the bike for a test ride after adjustments to check performance under real riding conditions. Make any additional tweaks needed to get the shifting dialed.
And that covers the full rear derailleur adjustment process from A to Z! Just following these steps methodically will get your shifting tuned up and performing like new again.
Common Rear Derailleur Adjustment Issues
Here are solutions to some of the most frequent problems that occur when adjusting a rear mountain bike derailleur:
Chain rubbing on derailleur cage in certain gears – Loosen the limiting screw on the side the chain is rubbing towards slightly to provide more clearance.
Chain won’t reach the largest rear cog – Turn the B-tension screw counter-clockwise to move the upper jockey wheel closer to the cassette.
Delayed shifting – Use the barrel adjuster to increase cable tension and eliminate slack causing slow shifts.
Getting familiar with how to troubleshoot these common issues will help you quickly diagnose and fix any adjustment problems.
Rear Derailleur Maintenance Tips
Proper ongoing maintenance will keep your rear derailleur adjusted optimally:
- Periodically check derailleur hanger alignment
- Keep pulley wheels clean of debris
- Apply lube to all pivot points
- Inspect cable for fraying and replace if needed
- Wipe grime off jockey wheels and cassette cogs
Catching issues before they worsen will prevent more significant drivetrain damage down the road.
Frequently Asked Questions
What tools do I need to adjust a rear derailleur?
The basic tools needed are 4mm & 5mm hex wrenches, a Phillips head screwdriver, cable cutters, and grease. A derailleur hanger alignment tool and bike work stand also come in handy.
How do I stop chain rub on my rear derailleur?
If the chain rubs the derailleur cage, adjust the limiting screw on that side inward slightly to provide more clearance. The B-tension screw can also help adjust clearance between the upper jockey wheel and cassette.
Why does my bike skip gears when shifting?
Gear skipping is typically caused by a rear derailleur in need of adjustment. Properly setting the limit screws, B-tension screw, and cable tension will help gears shift smoothly without hesitation.
Can I adjust my rear derailleur myself?
Yes, adjusting a rear derailleur is a DIY project any mountain biker can tackle at home with basic mechanical skills and the proper tools. Following step-by-step instructions makes the process straightforward.
How often should I adjust my rear derailleur?
A general rule of thumb is to check rear derailleur adjustments every 2-3 months. But anytime you experience shifting issues like skipping, hesitation, or noise, it means your derailleur needs to be tuned up.
Adjusting the rear derailleur on your mountain bike, specifically knowing how to adjust rear derailleur on a mountain bike, is essential to keep your drivetrain performing well.
Follow the step-by-step process using the proper tools and settings to dial in shifting that is fast, quiet, and accurate across every gear. Taking time to regularly maintain and fine-tune your derailleur will lead to a more enjoyable and problem-free riding experience.
Related Post You may be interested to Read: How To Adjust Mountain Bike Brakes? How To Remove Mountain Bike Pedals? How To Bleed Mountain Bike Brakes?
Mahin Abrar is a passionate writer and outdoor enthusiast. As a regular contributor to Bikepics.net, Mahin shares his knowledge and experiences in the fields of biking, cycling, hiking, and camping. With a deep understanding of these activities and a keen eye for detail, he offers valuable insights and practical advice to help readers get the most out of their adventures. Whether you're a seasoned pro or just starting out, Mahin's writing is sure to inspire you and guide you on your journey.