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15 February 2025

9 minute read

How to Fix a Bike Chain That Keeps Falling Off

You've probably experienced the frustration of riding your bicycle only to have the chain slip off repeatedly. It's a hassle you're ready to leave behind. What causes this pesky problem, and how can you solve it?

Jake Fieldsend

Jake Fieldsend

Founder & CFO

How to Fix a Bike Chain That Keeps Falling Off

You've probably experienced the frustration of riding your bicycle only to have the chain slip off repeatedly. It's a hassle you're ready to leave behind. What causes this pesky problem, and how can you solve it? This article provides practical insights and a step-by-step guide to help you fix a bike chain that keeps falling off, ensuring safer and smoother rides. Let's dive into the reasons why chains misbehave and how you can regain control over your cycling adventures.


1. Understanding Why Your Bike Chain Falls Off


1.1 Common Reasons for a Chain Falling Off


Your bike chain seems to have a mind of its own, right? It's not just you—various mechanical factors could be to blame. Here's what usually goes wrong:


  • Poor Alignment: If your chain isn't properly aligned with the gears, it's more likely to drop when shifting. This misalignment can occur due to improper derailleur settings or bent components.
  • Loose Components: Over time, bolts and nuts may loosen, causing components like the derailleur to shift out of place. Regular inspections can prevent this issue.


To avoid these pitfalls, make sure to regularly check alignment and tighten any loose parts. Spotting these signs early on can save you a lot of trouble during a ride.


Pro-tip: Always keep a set of Allen keys in your saddlebag for on-the-go adjustments. You never know when you'll need a quick fix!


1.2 Impact of Wear and Tear on Chains


Chains face constant stress with each pedal stroke, which eventually leads to wear and tear. Let's break down what this means:


  • Material Wear: A worn chain can develop 'stretch', making it too slack to fit snugly on gears. Regular use wears down the metal, which lengthens the chain and affects its fit.
  • Damaged Links: Bent or damaged chain links reduce its efficiency and stability. You risk sudden failures if damage isn't addressed.


Keeping your chain well-lubricated and cleaning it regularly can slow down wear, increasing its lifespan and reliability. Prevention is always better than a costly breakdown on the road!


1.3 How Incorrect Chain Length Affects Stability


Believe it or not, chain length plays a crucial role in keeping things running smoothly. Here's why it matters:


  • Too Long: A chain that's too long will sag and catch on other components, leading to increased chances of dropping. The extra slack gives it room to jump gears, especially on bumpy terrains.
  • Too Short: If your chain is too short, it can cause undue stress on the gears and derailleur, resulting in poor shifting and potential damage.


To measure and adjust the length of a new chain, consider the 'Big-Big' method: lay your chain over the largest chainring and largest rear cog, then add two extra links for proper tension. This will help achieve the perfect balance for smooth cycling.


Pro-tip: Count the links of a functioning old chain before replacing it. This ensures the new chain matches the required length, preventing potential fitting issues.


2. Step-by-Step Guide to Fixing a Bike Chain


2.1 Inspecting the Chain and Drivetrain


First things first, get up close with your chain and drivetrain. Begin by checking for any apparent dirt, gunk, or rust that might be affecting the chain’s performance. A clean chain is less likely to slip.


  • Look for any twists or unusual bends in the chain links. A twisted link can cause the chain to derail.
  • Examine the chain links for wear. Stretched or worn chains may not mesh properly with the sprockets, often resulting in the chain coming off.


Pro-tip: Use a chain checker tool to determine if your chain has elongated beyond its operational limits. Visit your local bike shop or online stores for this handy tool.


Consider the drivetrain components next. You need to ensure that the chainrings, cassette teeth, and derailleur pulleys are not overly worn or damaged.


  • Inspect for broken or missing teeth on both the cassette and chainrings.
  • Check if the derailleur hanger is straight and not bent.


Pro-tip: If you notice substantial wear or damage on any drivetrain components, replacing them might be more cost-effective than continual repairs. Keeping a spare chain on hand saves time and ensures you’re never caught off guard by a broken chain during a ride.


2.2 Adjusting the Chain Tension


If you've found that the chain isn’t staying on, it might be too loose. Adjusting the chain tension can help. Here’s how:


  1. For single-speed or fixed-gear bikes, adjust the rear wheel by loosening the axle nuts. Move the wheel backward to tighten the chain or forward to loosen it.
  2. For bikes with derailleurs, use the derailleur screw (often marked 'B') to adjust the tension. Remember to test after each adjustment to ensure the chain runs smoothly.


Pro-tip: A properly tensioned chain should have a gentle play of about half an inch to an inch. Too tight can strain components, while too loose can risk the chain dropping.


After tensioning occasionally, you might need to fine-tune by checking the derailleur settings. Misalignments might still cause the chain to jump.


  • Make sure the derailleur aligns properly along the cassette.
  • Fine adjustments can be made using the barrel adjuster on the derailleur cable.


Pro-tip: A quick tip is to run the chain through the entire range of gears after adjusting to ensure seamless transitions without dropping. This final check is key to spotting any tension issues.


2.3 Realigning the Derailleur for Optimal Performance


If your derailleur is slightly off, problems are bound to occur. Realigning it is crucial:


  • Begin by adjusting the high and low limit screws on the derailleur. They ensure the chain doesn't slip off the largest and smallest sprockets.
  • Use a small Phillips screwdriver for precise adjustments. Loosen or tighten the screws as necessary.


Pro-tip: The trick to correctly adjusting the derailleur is listening and observing. As you shift through gears, subtle clicking sounds often indicate misalignment.


Beyond the screws, ensure the derailleur hanger is not bent, as this can severely affect gear shifting.


  • Use a derailleur hanger alignment tool to check for warping. Even a slight bend can misalign gear changes.


Pro-tip: Regularly maintaining the derailleur can prevent bigger issues. Keeping a small toolbox with spare parts like screws and few essential tools ensures you’re prepared for on-the-go adjustments. If persistent misalignment occurs, it might be time to replace the derailleur or seek expert help.


3. When to Seek Professional Help


3.1 Identifying Issues Beyond DIY Repair


Not every bike chain issue is fixable with a DIY approach. If you've tried adjusting your chain tension and realigning the derailleur, but your chain still falls off, there might be deeper issues. Cracks in the frame or severe drivetrain misalignments will require specialised tools and knowledge beyond basic home repairs.


Consider these problems as signs it's time for professional intervention:

  • Persistent Chain Dropping: Despite frequent adjustments, the chain continues to derail.
  • Irregular Gear Shifting: Gears don't shift smoothly or skip unexpectedly.
  • Visible Frame Damage: Cracks, warps, or unusual bends in the frame.
  • Bent Chainring Teeth: This indicates potential for chain slippage.
  • Drivetrain Misalignment: Visual misalignment or angle derailing chain path.


Pro-tip: Regular checks for frame cracks and drivetrain misalignments can prevent long-term damage and costly repairs.


3.2 How Bikebook Can Assist in Finding Local Mechanics


Bikebook simplifies the often cumbersome task of locating a qualified bike mechanic. Our platform saves both time and effort by providing an easily navigable database of skilled local mechanics right at your fingertips. Simply enter your postcode to kickstart your search, making the process of finding reliable service just a few clicks away.


Key advantages of using Bikebook include:

  • Comprehensive Database: Access thousands of local and mobile bike mechanics.
  • Customised Search: Filter mechanics by qualifications, proximity, and services offered.
  • Verified Reviews: Read genuine customer feedback to inform your decision.
  • Free Use: No hidden charges; just a quick way to connect with experts.
  • Support Local Business: Engage with mechanics passionate about their communities.


Pro-tip: Use Bikebook to schedule regular bike servicing to prolong the life of your bike and ensure smooth rides.


3.3 The Benefits of Regular Professional Bike Servicing


Regular professional bike servicing can detect and rectify minor issues before they deteriorate into larger, more costly problems. This preventive approach not only enhances bike performance but also extends its lifespan. Frequent servicing ensures components like chains, gear systems, and brakes function optimally.


Consider these benefits when opting for professional bike servicing:


  • Longevity: Increases the durability and lifespan of your bike components.
  • Safety: Makes sure brakes, chains, and gear systems work correctly.
  • Performance: Keeps your bike's performance at its peak level.
  • Resale Value: Maintains and possibly increases the bicycle's resale value.
  • Cost-Effectiveness: Preventative maintenance minimises the risk of expensive repairs down the line.


Pro-tip: Schedule a professional bike service at least once every six months to catch and fix any emerging issues promptly.


In conclusion, while many chain issues can be tackled at home, it's vital to understand the point where professional intervention becomes necessary. Regular maintenance, coupled with expert advice from local mechanics sourced through platforms like Bikebook, ensures your bicycle stays in prime condition, elongating its durability and reliability. Ready to find trustable local expertise? Bikebook can help you connect with top-notch mechanics in your area, facilitating a smooth ride every time.


Frequently Asked Questions


Why does my bike chain keep falling off?

A bike chain may fall off due to various reasons such as incorrect tension, misaligned derailleur, worn-out chain components, or improper installation. Regular maintenance and checks can help prevent such issues.


How do I get my bike chain to stay on?

To keep your bike chain secure:

  • Ensure Correct Tension: Adjust to the optimal tightness.
  • Check Derailleur Alignment: Align for smooth shifting.
  • Inspect for Wear and Tear: Replace worn components.
  • Clean and Lubricate: Maintain cleanliness and lubrication.
  • Secure Fasteners: Tighten all related components properly.


Why does my bike chain come off when I pedal hard?

Pedalling hard might cause the chain to slip if there's too much tension or misalignment. Inspect chainring and derailleur positions, and ensure the chain is correctly routed.


How to stop a chain from coming off?

To prevent your chain from detaching:

  • Align Derailleur: Ensure derailleur positioning aligns with chainrings.
  • Adjust Tension: Maintain proper chain tension.
  • Check Chain Length: Ensure appropriate length and avoid excess slack.
  • Inspect for Component Wear: Replace any worn links or teeth.
  • Regular Maintenance: Regularly clean and lubricate the chain.

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