Removing and Replacing the Cogs
The cogs must be removed to replace spokes on the rear wheel. Or you may need
to get a specific cog free of the rest to straighten out a bent tooth.
Eventually, the teeth become worn and the entire cassette must be replaced.
(Keeping your chain clean, and replacing it every 1000 miles, helps your cogs
|To remove the cogs, you need a freewheel tool and a chain section. The
freewheel tool has a toothed ring on one end that fits into the locking wheel of
the cogs. The other end is designed to fit a wrench.
Freewheel tool. The bumps on the side
of the wheel fit into the corresponding slots on the lockring. A wrench
attaches to the end the fingers are holding in the photo.
||If you have a cassette immobilizing tool (a "chain whip," which is like a wrench with a
section of chain on the end), wrap it around the cogs. The bar should be
on the clockwise end of the curve of the chain. The small loop of chain
sits against the teeth to anchor the handle of the tool, while the loose
piece of chain wraps around the cassette.
After inserting the freewheel tool into the
lockring, use a wrench to turn it counter-clockwise
to remove the lockring.
|If you don't have a chain whip, just use a section of chain to immobilize the freewheel.
I just take an old broken chain, drape it
over the top of the big cog, then stand on the other end with my foot.
||Lift the cogs off. Each cog must fit on its neighbor
exactly, and the spacing rings between the smaller cogs must not be mixed
up. It's best to keep the whole mess together as a unit.
If you need to replace or work on a single cog, lift off the cogs down
to the damaged cog, keeping everything else together.
If you're straightening a rock-bashed tooth on a cog, note the trend of the
teeth before and after the bent tooth. The teeth on the cog are NOT exactly
straight. They have a tilting pattern that helps the teeth pick the chain up
from the adjacent cog. Note where the damaged tooth fits into this pattern, and
bend it to the proper position.
||Replace the cassette. The center of the cassette, and the
smaller freestanding cogs, has square teeth that fit onto the shaft of the
freewheel at one, and only one, position. Turn the cogs until these inner
teeth line up with the slots on the freewheel shaft.
Using the freewheel tool, replace the lockring. You don't need a chain whip
for this. As you turn the lockring clockwise, the freewheel mechanism engages
the wheel. Just keep the wheel still as you rotate the lockring.
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