How to Replace Your Lockring & Cog: Removing Fixie Sprocket

This article will show you what a fixie cog is, when you should replace it, and how to replace it. Instructional video included!

Have you ever needed to change a bike cog but didn’t know where to start? Unfortunately, this could be time-consuming, and locating the appropriate tools can be difficult. But how do you go about replacing a bicycle cog?

This article will teach you what a cog is, when you should replace it, and how to replace it.

Remove the bolts on the rear wheel. Take the chain off the rear wheel cog. Remove the bike’s rear wheel from the frame. And use a chain whip and a cog tool to replace the cog. A lot of force will be required.

Thumbnail for a blog post how to replace your lockring & cog: removing fixie sprocket
Thumbnail for A Blog Post how To Replace Your Lockring & Cog: Removing Fixie Sprocket

What is a cog?

A cog is a gear on the rear wheel that the chain attaches to. Fixed gear bikes only have one gear, this one gear, and thus one cog. For example, the Brooklyn Fixed Gear logo features a single orange cog.

Below are a few popular fixie cogs in different sizes. Some come with lockrings, and some don’t.

My favorite fixed-gear bike (right now):

State Bicycle Co. Black Label 6061

Best overall fixed gear bike state bicycle co 6061 black label v2
My favorite fixed-gear bike (right now):

State Bicycle Co. Black Label 6061

This is my daily ride, my trusty Black Label. It’s lightweight and beautifully crafted. Looks like a beast and rides like one too. I upgraded the saddle, but everything else is pretty much as it was out of the box. I highly recommend it.

What is a lockring?

A Lockring is a thin locknut to prevent a threaded assembly from unscrewing. Lockrings are used in fixed-gear hubs to restrict the sprocket from unscrewing when the cyclist opposes pedal motion. Traditional bottom brackets use a lockring on the adjustable cup to keep the adjustment in place.

When should I change my cog?

You should upgrade your cog if it’s damaged or worn down; looking at the teeth on the cogs to check whether they’re worn down is one way to identify if you need to update a new cog.

While only one speed is available on a fixed-gear bike, they are a great way to get around. You don’t have to buy a new bike if you prefer a different speed. Changing the size of the cog on the back wheel changes the rate of travel. So, you should also consider a new cog if you want to change the gearing on your fixie.

The materials you’ll need to replace the bike cog.

Below are some of the common tools you will need if you are replacing your fixed gear’s cog.

  • Cog of appropriate size
  • A lockring
  • 15mm socket wrench
  • Lockring wrench
  • Chain whip

Need some help finding the right tools? Look no further. Below are three of the most popular Park tool to remove your cog and lockring.

Man riding a white fixed gear or single speed bike with a messenger bag. Source: adobe stock
Image of a man riding a white fixed-gear or single-speed bike with a messenger bag. Source: Adobe Stock

How do you replace a bike cog?

Here are some methods and recommendations to help you replace your bike cog. The result could be greasy fingers and soiled clothing. Wear protective gear like gloves and old clothes you don’t mind soiling. A bit of grease will also be present on the cog.

  1. Remove the rear wheel bolts

    Using an adjustable wrench, remove the 9.5mm bolts attached to the back wheel. On either side of the wheel is where you’ll find the bolt.

  2. Loosen the chain tension screw (if applicable)

    Loosen the chain tension screw that measures 4mm by 50.8mm using a hex key. Each of the sides of the wheel has a screw attached to it.

  3. Remove the wheel

    Take the chain from the cog that is on the back wheel. Next, take the rear wheel off the bike and remove it from the frame.

  4. Remove the lockring

    Utilizing a lockring wrench, take off the lockring that is located on the back tire. Turning the wrench in the clockwise direction will loosen the lockring.

  5. Loosen the cog

    You will need an adjustable pair of pliers and a chain whip to loosen the cog. Whip the chain through the cog-like a whip. When you pull the chain whip handle up, the cog will rotate in the opposite direction clockwise. To dislodge the cog will need a significant amount of effort.

    Position the chain whip accurately on the cog before attempting to remove it. At first, you’ll need to apply some serious force to the cog to loosen it. Your hand could be sliced on the cog or fall to the floor if the tool slips out of your hand.

  6. Replace the cog

    The remaining portion of the cog can be removed with your hand. Put in a new gear in its place.


  • Cog of appropriate size
  • Lockring
  • 15mm Socket Wrench
  • Lockring wrench
  • Chain whip

If you want even more tips, watch this video called “How To Change A Track Bike Or Fixie Sprocket” from The Global Cycling Network YouTube Channel.

A video called “How To Change A Track Bike Or Fixie Sprocket” from The Global Cycling Network YouTube Channel.

Frequently asked questions (FAQs)

Do you still have questions? Below are some of the most commonly asked questions about replacing bicycle cogs.

What is the best fixie gear ratio?

The typical gear ratio for a fixie is 44/16. Because of this ratio, you can accelerate quickly enough to tackle steep inclines while maintaining a respectable enough top speed to traverse flats and undulating terrain.

Why does a fixie gear ratio matter?

Your ability to skid is also determined by your fixie ratio, which influences your speed and acceleration. Only one-sided skidding is possible with a greater ratio. Therefore, it could be the best choice for you. On the other hand, it’s easier to run lower ratios if you’re ambidextrous because you can skid with either foot (skid positions come around less frequently on lower ratios).

How do you choose a fixie gear ratio?

If you’re just starting a fixie, a standard ratio is recommended, around 44/16. However, if you want to experiment with different ratios until you discover the one that works best for you on your fixie, is a fantastic free resource that can help you get there.


All bike parts are vital in ensuring a smooth ride. So, when something goes wrong with your bike, you should never hesitate to take it in for repair. But before you do, ensure you understand everything about the problem and how it may be rectified. Then, following our tips and tricks, you can easily fix the problem without calling professionals.

This article covered what a cog is, how to replace a cog, and provided tips on choosing the right one for your needs. Here are some key takeaways:

Key takeaways

  • The gears on the back wheel are known as “cogs.”
  • A worn chain will also cause your cassette and chainring teeth to wear out.
  • Looking at the teeth on the cogs to check whether they’re worn down is one way to identify if you need to update a bike cassette.
  • Clockwise refers to a cog threaded clockwise (left-hand) around a hub.
  • Your derailleur has a cable connecting cogs to move them up or down against friction from cables.
  • The derailleur is a mechanism that allows the rider to shift their gears.
  • Most freehub hubs are the same and can be found on almost all road bikes, mountain bikes, and cyclocross bicycles.
  • A freewheel is a cog attached to the outside of a sprocket that works with a freewheel.
  • Your chain’s freewheel part needs to be taken off and replaced with new cogs.
  • The most common way to remove an axle is using a specially designed tool called a “hex wrench” (or hex key).

Did we cover everything you wanted to know? Let us know in the comments section below (we read and reply to every comment). If you found this article helpful, check out our full blog for more tips and tricks on maintaining your bike. Thanks for reading, and stay fixed.

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Bradley Knight Image
Written by Bradley Knight, Staff Writer

Hey there! My name is Bradley, and I've been riding fixed for years. I love all the joy and pain that comes with this unique style of cycling and the passionate community that drives it. If you love fixed-gear bikes, this is the place for you.

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Jordan is a seasoned editor with over seven years of experience. His passion for writing and storytelling started when he was a teenager, spending countless hours reading books and creating his own stories.

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