Fixed Gear MTB: Remove/Install Track Cog

A new track cog was puchased for an off-road fixed gear mountain bike. The goal was to remove the old track cog and install the new track cog.

The Problem

The lockring was easy to remove, but the old cog was stuck onto the hub.

First attempt, a chain whip was used to try and loosen the cog, but the cog would not budge.

Second attempt, the lockring was removed and the wheel was placed back on the mountain bike. From there, braking was attempted as was stomping on the pedals in reverse direction. Unfortunately the cog would not loosen.

Reverse Rotafix

After two failures, the internet was used to uncover another method know as the Reverse Rotafix.

According to Wikipedia, Rotafix

is a method of tightening or loosening a sprocket on a track bike or fixed gear bicycle.

The chain is removed from the chainring and rests around the bottom bracket shell and on the sprocket with the rear wheel in the horizontal track ends. The chain is folded over itself such that the bottom half of the chain is trapped between the sprocket and the upper half. The sprocket is then prevented from turning because the chain is wrapped around the bottom bracket. It is essential to take steps to protect the paintwork on the bottom bracket shell from damage by the chain.

Removing the sprocket is done by reversing the chain fold so that it is on the bottom, and turning the wheel forwards so that the sprocket turns counterclockwise. This is called the Reverse Rotafix.

  • However due to risk of damage to the bike and parts, the Reverse Rotafix was not an option.

The Final Solution

Chain whip + rubber mallet. Yes, it was that simple!

Instructions: Fixed Gear Cog Removal

  1. Remove the rear wheel from the mountain bike.
  2. Remove the lockring (reverse threaded) with a spanner wrench. Rotate clockwise to loosen it.
  3. Hold the wheel upright, with the cog facing away from your shins.
  4. Attach the chain whip to the track cog for rotating counter-clockwise.
  5. Wrap a cloth around the handle of the chain whip.
  6. Wear some gloves and hold the chain onto the cog.
  7. With the other hand hold the mallet.
  8. Whack the end of the chain whip handle (counter-clockwise direction) repeatedly with the mallet until the cog comes loose.
  9. Unthread the cog the rest of the way by hand.

Instructions: Fixed Gear Cog Installation

  1. Liberally grease the hub’s track threads and lockring threads.
  2. Liberally grease the cog’s threads.
  3. Gently rotate the cog clockwise onto the hub’s track threads. Avoid cross-threading as it can ruin the hub.
  4. Use a chain whip to tighten the cog onto the hub.
  5. Liberally grease the lockring’s threads.
  6. Gently rotate the lockring counter-clockwise onto the hub’s lockring threads. Lockring is reverse-threaded.
  7. Use a spanner wrench to tighten the lockring (counter-clockwise).
  8. Install the rear wheel onto the mountain bike. Pedal forward and stomp forward hard on the pedals.
  9. Remove the rear wheel from the mountain bike.
  10. Tighten the lockring some more, counter-clockwise, with a spanner wrench.

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