How does a cassette work?
A modern mountain bike's cassette, no matter how many speeds it has, slides onto the rear hub's freehub body and is tightened down with a lockring. Splines on the freehub body ensure that the cassette's shift ramps are properly aligned as the manufacturer intended. The hub's clutch mechanism, the part that allows you to coast or put down power, is built into the freehub body itself, meaning that the cassette can be removed without having to dive into the hub's internals. Removing the cassette involves loosening the lockring with a special splined tool while holding the cassette with a chain whip, a type of long wrench with a section of actual chain on the end that engages the cog's teeth. While removing the cassette isn't included in routine maintenance, it does allow for easier cleaning of the drivetrain.
Some helpful pointers before you begin:
The cassette is made up of cogs, some separate and some on a carrier as shown above, that feature notches that mate with splines on the freehub body.
• While both SRAM and Shimano cassettes can often be removed with the same tool, there are a number of different lockring tools that may or may not be best suited to your hub depending on the configuration. Your best bet is to take your rear wheel into your local shop and have them show you which model is ideal.
• Lay out the cogs and spacers on your workbench in the exact order that they were removed in. Your bike won't shift correctly if a spacer is installed in the wrong position.
• If installing a new cassette take note of the order of its parts when removing it from the box.
• Although we didn't show it below, the wheel's quick release skewer can be used to hold the lockring tool in place while you crack it loose. This is especially helpful if the engagement between the tool and lockring is shallow, as can sometimes be the case.
• Be careful not to cross thread the lockring while reinstalling the cassette. Doing so can sometimes damage the threads on the freehub, which opens a can of worms on the entire repair. Likewise, aluminum lockrings can be fragile - take your time.
• If installing a new cassette it is important to also use the new lockring if the new smallest cog is of a different size to the old one (11 and 12 teeth are the most common sizes
). Eleven tooth cogs use a smaller diameter lockring than larger twelve tooth versions. Using the twelve tooth sized lockring on an eleven tooth cog will prevent the chain from fully engaging the threads, causing it to skip under load while in the highest gear.What's needed:
• Cassette lockring tool
• Chain whip
• Large adjustable wrench
or vice (in place of a freewheel tool wrench
• Grease or anti-seize
You'll need a chain whip, lockring tool and large adjustable wrench to do this job, although a vice can be used in place of the wrench.
Step 1 - Remove the rear wheel from the frame and slide out the skewer, being careful not to lose the centering springs on each side. Install the splined lockring tool so that it is fully seated into the notches. If the engagement is quite shallow and the lockring tool is hollow you can use the QR skewer to hold it in place by reinstalling it through the hub and tool and snugging it down. Some lockring tools feature a pin that takes the place of a skewer.
Step 2 - Install the chain whip, making sure that the tool is fully engaged with the cog. The purpose of the chain whip is to hold the cassette/freehub from spinning while you loosen the lockring. If you are facing the cassette you will want the handle of the tool extending to the right as shown above.
Step 3 - It is now time to loosen the lockring. With the wheel face up on the workbench use a large crescent to turn the lockring tool counter clockwise while pulling the chain whip clock wise to hold the cassette/freehub in place. Apply even pressure to prevent the chain whip from jumping off of the cog, but if it does so repeatedly it likely means that that particular cog is so worn that the tool is actually slipping off. Move up to a larger cog and try again. If you've used the QR skewer to help hold lockring in place you'll need to remove it in order to further loosen the lockring once it's been cracked free.
Some overly tight lockrings may require a bit of body english in order to crack them loose. If this is the case place the wheel upright on the ground in front of you with the cassette facing away. While standing over the wheel, with the tools in the orientation shown above, use your body weight as an aid to help loosen the lockring by pushing down on both the wrench and chain whip.
Step 4 - Unthread the lockring and set aside. Slide the cogs up and off of the freehub, taking note of where each spacer sits, and lay them out on the workbench in a safe spot. They need to go back on in the exact order that they were removed for your bike to shift properly.
Cassettes can sometimes become stuck on aluminum freehub bodies due to the them gouging into the softer metal. This is common when the steel cogs are spaced separately instead of attached to a carrier that spreads out the load better. A screwdriver can be used to gently pry the cogs loose (be careful not to bend them), or used to tap them loose from the back side with a hammer.
Step 5 - Now is a great time to give the cogs and freehub body a proper cleaning, but be sure not to misplace any spacers while doing so. Inspect the cassette for any broken teeth or burs that can be cleaned up with a file.
Step 6 - Take note of the freehub's splines and the notches on the cogs before reinstallation. The cogs will only slide onto the cassette in one orientation thanks to an odd sized spline that is slightly smaller in thickness than the rest. This ensures that the cassette's shift points will all line up as they were designed to. The spline and corresponding notch are shown above circled in red.
Step 7 - While there is always debate about giving the freehub a light coating of grease or anti-seize, we don't ever recommend doing so. Neither will prevent the cassette from gouging into the freehub body, and a steel cassette and freehub body has very little chance of corroding enough to ever become rusted together (that same goes for aluminum cassettes and F/H bodies as well). What the grease will do, though, is attract dirt and grime and make a mess of things. The only place where a small dab of grease or anti-seized should be used is on the lockring threads to allow it to be loosened easier down the road.
Step 8 - Align the cogs correctly and slide them down onto the freehub body, being careful to install everything in the exact order required - spacers included. Some cassettes will use a large 'carrier' that many of the cogs are attached to, turning them into a single unit, while some others may use separate cogs throughout the entire cluster.
Step 9 - Some cassette and hub combinations, especially those fitted with 10 speed cassettes, will result in the last (smallest) cog not engaging the freehub's splines fully until pressure is applied. Make sure that the last cog is properly aligned before pressing it down with one hand while threading the lockring clockwise with the other until it is snug.
Step 10 - Take a close look to make sure that the cassette is spaced evenly before using a wrench to fully tighten the lockring. Look from the rear while slowly rotating the cassette. If you spot any wobbles or unevenness between the cogs you'll need to disassemble the cassette and find your mistake.
Do you have any pointers on removing and installing a cassette? Share them below!
Step 11 - Finish tightening the lockring by using a crescent wrench to turn it clockwise until it is quite snug. A torque of at least 360 inch/pounds is recommended. The QR skewer can once again be used to hold the tool in place (not shown).
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