Replacing the Lockring and Cog on a Fixed-Gear Bike

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Introduction: Replacing the Lockring and Cog on a Fixed-Gear Bike

So you love your fixed gear bike, but that back cog is just a little too slow, and you want a slightly tougher drive ratio. Or maybe your lock ring is coming a little loose, and you need to remove it and apply some locktite. Maybe you're even starting to build your own bike, and need to install the cog and lock ring on the back wheel. Whatever the cause, removing and replacing the cog and/or lockring is a regular part of maintaining a fixed gear bike. This guide is here to help you walk through the process quickly and easily, so you can get the most out of your fixed gear.
If you are just installing the cog and/or lockring, and don't need to remove an old one, start from Step 5.

Step 1: What You'll Need

Materials and Tools:

  • Singlespeed or track wheel
  • Cog of appropriate size
  • Lockring
  • Lockring wrench
  • Chain whip or chain pliers
  • Grease
  • 15mm Socket Wrench

If you are unsure what any of these are, check the glossary below.

Glossary

Chain Whip - The chain whip is a tool used to tighten and loosen cogs and cassettes on bikes. A chain whip has a handle, with a section of chain attached to the end. When choosing a chain whip, whips with longer handles are usually better, as they help you get more leverage on the cog. Personally, I use this chain whip from Park Tools.

Cog - The cog is the gear on the back wheel. The size cog that you use is up to you. A smaller cog will let you go faster, but will make it harder to a accelerate and go up hills. The appropriate cog size is relative to the size of the chainring (the gear on the pedals). This article gives some good information about some of the common gear ratios. I personally use a 16-tooth cog and a 46-tooth chainring.

Lockring - This is the notched, circular piece threaded against the outside of the cog. They can come with anywhere from two to six notches, and are reverse-threaded, so they are loosened by turning to the right. Some examples of lockrings include:

Lockring Wrench - The lockring wrench is a specialized tool specifically for tightening and loosening the lockring on the back wheel. The wrench wraps around the lockring, and has one or two teeth that fit into notches on the lockring. If you don't already own one, you will need to buy one. I personally use this one

Step 2: Remove the Back Wheel

Above: loosening the mounting nuts on the rear wheel; removing the chain from the cog; removing the rear wheel from the frame

Before you're able to access the lockring and cog, you'll need to get the back wheel off of your bike. If you already have the wheel off of your bike, feel free to skip to step 3.

Steps:

  • Use the 15mm socket to loosen the nuts holding the back wheel in place.
  • Slide the wheel as far forward as it can go. This will loosen up the chain around the back cog.
  • Pull the chain off the back cog once it is loose enough, and let it hang.

CAUTION: If you have to spin the wheel to get the chain off, keep your hands and clothing clear of the cog. If your hand gets caught between the cog and the chain while it's spinning, it will be pulled through and you could easily lose a finger.

  • Pull the back wheel out of its slots in the frame, and move on to the next step.

Step 3: Remove the Lockring

Above: Using the lockring wrench to loosen the lockring

The next step is to take the old lockring off of the back wheel. If you are unsure of what this means, check the glossary in the Introduction.

Steps:

  • Place the lockring wrench around the lockring
  • Turn to loosen it, as you would with a normal wrench. Please Note that the lockring is reverse threaded, so you will have to pull to the right to loosen it.

CAUTION: Be sure to hold the lockring wrench on tightly. It is easy for the tool to slip off, which can cause injury or damage the lockring. It will take a lot of effort to get the lockring to break free, so be careful not to let the wrench slip.

Step 4: Remove the Cog

Above: Using the chain whip to loosen the cog

Once you've removed the lockring, you're ready to remove the cog.

Steps:

  • Wrap the chain whip around the cog.
  • Hold on to the wheel, and turn the whip handle to the left. Be aware that the cog will be on tightly, so you will likely have to put a lot of force in to get it to break free.
  • Turn cog to the left by hand to get it the rest of the way off.

Step 5: Prepare the Threads

Above: Applying grease to the cog theards

Now that you've gotten the cog and lockring off, you'll need to get ready to put the new cog and lockring back in place. At this point, feel free to do whatever work you might need to do on the lockring or cog. If you are planning on painting them, do so now.

Steps:

  • Optionally, consider applying some loctite to the threads on the wheel. Loctite is a glue-like paste that will help prevent the lockring from coming loose while you ride. If you want to do so, use a rag or paper towel to spread a dab of loctite on the threads that hold the lockring.
  • Use a rag to smear a small amount of grease on the threads that will hold the cog. This will allow the cog to tighten down more easily.

Step 6: Install the New Cog

Above: Using the chain whip to tighten the lockring

At this point, everything is ready to be put back together.

Steps:

  • Start threading the cog onto the wheel by hand. Obviously, if you are replacing the cog, you should be putting the new cog in place. The cog is threaded normally, so righty tighty, lefty loosey.
  • Use the chain whip to tighten the cog as tightly as you can.

CAUTION: Be sure to tighten the cog as tightly as you can. You don't want the cog moving about while you are riding. If you feel like the chain is slipping when the bike is all back together, it's likely that it's actually the cog turning on the threads because the cog and lockring aren't tight enough. If this happens, come back to this step, and really crank down on the cog and lockring.

Step 7: Install the New Lockring

Above: Tightening the lockring in place with the lockring wrench

Steps:

  • Thread the lockring onto the wheel by hand. Again, the lockring is reverse-threaded, so you will have to turn it to the left to tighten it.
  • Put the lockring wrench in place around the lockring.
  • Turn the wrench to the left to tighten the lockring in place. As mentioned in the previous step, be sure to tighten this as tightly as you can. You don't want the cog to loosen while you're riding.

Step 8: Put the Back Wheel in Place

Above: tightening the cog-side nut with the chain properly tensioned

Putting the wheel in place can be very tedious. You will need to give the chain enough tension that it won't sag or slip on the cog, aving the chain too tight will prevent the wheel from spinning freely. Getting the balance while keeping the wheel straight may take a few tries.

Steps:

  • Slide the rear while back into the slots on the frame.
  • Put the chain around the cog.
  • Pull the wheel back so the chain is taught around the cog.
  • Tighten the nut on the cog-side of the wheel.
  • Straighten the wheel in the frame, and tighten the other nut.
  • If the chain is too tight or too loose, loosen the cog-side nut, shift it forward or back, and tighten it again.
  • If the wheel is out of line (i.e. pointing to the left or right), loosen the other nut, straighten the wheel, and tighten it again.
  • Repeat the last too bullet points until the wheel is straight and the chain is taught.

Once the wheel is aligned and the chain is taught, your bike should be ready to ride.

CAUTION: Ride with extreme care when testing out these changes. If the cog and lockring are too loose, the cog can slip, which could prevent you from stopping quickly, or could jolt the bike enough to cause you to lose your balance. Put on a helmet and ride around gently for a few minutes and get a feel for the new gearing to avoid an injury if anything is wrong.

Once you have ridden enough and are confident that the bike is safe, you're free to enjoy your bike. Ride safely!

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    Excellent instructions. This is something that might not be useful to the casual browsers on the site, but anyone searching specifically for this procedure will be thrilled to find this Instructable. Thank you for taking the time to write up the process!!