Here is a simple guide for disassembling the cassette cog for you
Most of us will spend the majority of our time on the bike in between half a dozen cogs meaning those cogs will wear more than less frequently used cogs, such as the 11 tooth cog. It is possible to replace a single cog but some cassettes don't have replacement parts or are a single unit and most often you're better off changing the whole thing.
Tools you will need
PaToolsols FR-5 lock ring tool
Large cresent wrench
Tips: carefully remove the rings and note each spacer and where it goes. The rings will only slide on the cassette in one direction. Add grease to the skewer before re-inserting it
Removing 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 last longer.)
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.
Removing the cassette
A bike cassette is one of the integral parts of your bikes drivetrain. The cassette is composed of cogs or sprockets that sit on the freebody hub and are controlled in place by a lock ring. The chain embraces around the cassette and the front chain ring of the bike shapes the closed circuit that generating the power by pedaling. Every element of the drivetrain will gradually wear over time and need to be removed and replaced.
The amount of cassette you should wear to cycle will largely depend on the amount you ride, the conditions you ride in, and how well you clean and maintain your drivetrain. You may speed up the abrasion of the chain, cassette, and chain rings by riding in the wet or not properly removing the dirt and grit from your chain. Incorrectly lubing your chain will also result in premature wear of your cassette.
Here is a simple guide for removing a cassette for you.
Before you remove the cassette you must first remove the rear wheel. To do this place the chain in the smallest chain ring on the front and smallest cog on the back. This will give you some chain slack and make it easier to remove the wheel.
What You Need:
Cassette lock ring removal tool
Work start by giving the cassette a spin it, it should spin freely. Next wiggle the cassette, it should have a little play but it shouldn’t be a lot. So the same thing with the axle, it should have no play at all. If you find a lot of play in either axle or cassette, that means you may have other issues and you might want to have a bike shop check it out.
Start by placing the chain whip on the cassette. This stops the cassette from spinning when you go to loosen the lock ring; insert the cassette lockring removal tool into the lock ring now, if it doesn’t fit then you most likely have the wrong tool. Then put the crescent wrench on the lock ring tool opposite of the chain whip. Hold the chain whip in place and push down on the crescent wrench, it should come right off. Note that it may make a clicking noise as you loosen it that’s normal. The lock ring a is regular thread so lefty loose. The cassette should put right off if it fight you, wiggle it as you pull. Make sure you keep your thumb on top so you don’t send the cogs flying across the room