This post discusses the direction of the threads found on single and multi-cog freewheels:
Definitions
1. Multi-cog Freewheel
Multi-cog freewheels represent a cluster of cogs with a built-in ratcheting mechanism. The purpose of the ratcheting mechanism is to functionally disconnect the freewheel from the hub and allow the cyclist to coast.
2. Single-cog Freewheel
Single-cog freewheels operate on the same principle as multi-cog freewheels.
The only difference is that there’s only one cog/gear.
Multi-cog Freewheel Threading
Freewheels are not reverse threaded. They screw onto the rear hub in a clockwise direction.
The reason for the thread direction is security. When you pedal forward, the rear cogs rotate clockwise and thus tighten the freewheel onto the hub even more.
If the threading was reverse, the pedaling motion would cause the freewheel to untighten and subsequently wobble.
For that reason, a freewheel on a bike that’s been ridden a long time is often notoriously tight and requires a lot of force and leverage to unmount it. Most people use a cheater bar (a pipe that slides onto a regular wrench as an extension).
To remove a multi-cog freewheel, you need the following tools:
- A removal tool that matches the splines/notches of the freewheel.
- Wrench
- Extension bar (needed if the freewheel is really tight)
Note: If you have an older freewheel (e.g., Suntour), it’s necessary to secure the removal tool to the freewheel via the quick-release.
Once everything is set, you have to rotate the wrench or socket anti-clockwise to untighten the freewheel.
Single-cog Freewheel
Single-cog freewheels also thread onto the rear hub in a clockwise direction. The reason is once again to ensure that the pedaling motion does not untighten the freewheel.
The removal process is also similar. The only difference is that you will need a different removal tool designed specifically for single-cog freewheels.
One example of such a tool would be the ParkTool FR-6 which removes 4-notch single-speed freewheels.
Disassembling a Freewheel
To disassemble a freewheel one has to remove the lockring holding the mechanism together.
The ring is reverse-threaded and unscrews clockwise.
In a perfect world, the lockring is removed via a spanner wrench, but more often than not, one needs to tap it with a punch or a nail.
Once the freewheel is free, you can use a spanner wrench made out of a spoke such as the one in the picture to fully untighten the lockring.
Important notes: If you try to remove the lockring above when the freewheel is off the wheel, you won’t be able to because the inner part of the freewheel will spin.
For that reason, it’s recommended to keep the freewheel on the wheel for the initial untightening (the hardest bit) and then fully unscrew the lockring once the freewheel is off the wheel.
Note: The lockring above holds the freewheel’s mechanism together, not the actual freewheel. Freewheels do not need a lockring preventing them from untightening from the hub because pedaling forward tightens the hub.
Fixed-gear Cogs
Some people may confuse fixed-gear cogs with a single-speed freewheel. However, the two are very different.
A single-speed freewheel has a ratcheting mechanism which disconnects the freewheel from the hub when pedaling backward or coasting.
For that reason, a single-speed freewheel does not need a lockring to hold it tight to the hub.
Pedaling keeps the freewheel secure, and when the rider backpedals, the cog is disconnected from the hub, and there’s no chance for the freewheel to untighten.
A fixed-gear cog, however, does not have a ratcheting mechanism. Thus, there’s no coasting option, and each backpedal stroke transfers a lot of force to the cog, the hub, and the wheel.
Since there isn’t a freewheel mechanism to reduce the strain on the cog, there’s a real chance for the cog to untighten during backpedaling.
For that reason, fixed-gear cogs require the use of a lockring which prevents the cog from unscrewing.
The lockring is reverse threaded and tightens counterclockwise so that it cannot untighten during backpedaling.
The purpose of the lockring is to prevent the cog from untightening. Pedaling forward tightens the cog, but backward pedaling untightens it. When the lockring is there, the cog has no room to move and thus cannot unscrew even during backpedaling.
If the cog on a fixed-gear bike unscrews, the cyclist loses the ability to brake via the pedals. Hence why the system is engineered in a way to prevent this outcome.
Summary: What You Need To Know
1. Single and multi-cog freewheels are not reverse threaded and tighten to the hub clockwise.
2. The lockring holding the two parts of a freewheel together is reverse-threaded and untightens in a clockwise direction.
3. Fixed-gear cogs tighten to the hub in a clockwise direction but require the use of a safety lockring which tightens counterclockwise. The function of the lockring is to prevent the cog from untightening during backpedaling.
