Inspecting Your Freewheel or Cassette

Just like other parts of a bike, a freewheel or cassette will eventually wear out and have to be replaced. You can identify a worn freewheel the same way you identify a worn chainring (see Chapter 10) — by the teeth. Here are some clues for identifying worn teeth on a freewheel or cassette:

✓ They no longer have sharp edges.

✓ They look like they’ve been filed down.

✓ They lack symmetry.

✓ They have the shape of an ocean wave.

If your chain is skipping when you apply force when pedaling, it may be due to worn teeth on either the freewheel or cassette cogs or the chainring. Examine both and replace them as needed.

Sometimes only one cog will wear out — if this happens, it’s usually the cog that corresponds with the gear you use most when riding. (For many bikers, this’ll be cogs with 15 to 18 teeth.) If you have just one cog that needs to be replaced, you may be able to buy just that one cog — although often buying the entire cassette or a freewheel is cheaper.

Cleaning the Freewheel or Cassette

Caring for a freewheel or cassette is pretty straightforward. Unlike other com­ponents of the bike, where you’re concerned about the internal parts, with freewheels your goal is to keep the outside of the cogs clean. Dirt and grime quickly work their way onto the surface of the cogs and in between them.

This buildup can muck up the chain, spread dirt around your bike, and cause premature wear for all the parts.

You don’t have to remove the freewheel or cassette to clean it.

To clean the freewheel or cassette, follow these steps:

1. Remove the rear wheel from the bike by following the directions in Chapter 7.

Removing the rear wheel gives you better access to the cogs.

2. If the freewheel or cassette is very dirty, wash it with soap and water.

Avoid spraying water directly. Use a brush on the freewheel as you wash the wheel.

3. If the freewheel or cassette is not overly dirty, clean it with a rag.

Drop an edge of the rag between each freewheel cog and, while hold­ing each corner of the rag with your hands, clean between the cogs in a back-and-forth motion.

Dip the cloth or brush in degreaser before using it. But try to keep the degreaser from getting on the tire.

4. To remove dirt that’s trapped between the cogs, use a narrow brush or a screwdriver to scrape it out.

Some manufacturers make a tool with a brush specially designed for this purpose.

If the freewheel or cassette is really dirty, try removing and soaking it in a degreaser.