Mountain Bike Maintenance

Fix your own bike…

Cassette (and freewheel) Removal & Cleaning

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Cassette (and freewheel) Cleaning

There are two types of rear gears (and so wheel hubs) found on MTB’s;

The freewheel is a one-piece cluster of sprockets which also contains the freewheel mechanism (the ratchets that allow the gears to spin freely in one direction but not the other, thus allowing the bike to coast, or freewheel).

The freewheel screws directly (see the middle picture above) to the rear wheel hub and can be fitted easily without the use of a tool as the force of the chain on the gears will tighten the freewheel into place, just take care that the threads have engaged cleanly and screw it down by hand as far as you can. For removal, the splined tool shown in the right-hand picture is inserted over the axle (with QR removed if applicable) and into the corresponding splines in the center of the freewheel then turned anti-clockwise.

Depending on how long the freewheel has been in place and whether or not the person who fitted it used grease or anti-seize on the threads, you may find it helpful if somebody else holds the wheel for you. Keep the wheel as horizontal as possible and use handle extensions (like a breaker bar or a length of pipe) if necessary for extra leverage.

Remember to apply a little grease or anti-seize to the threads when you refit.

The most common type of rear gears on modern 8 and 9 speed MTB’s is the cassette. As the design allows the axle bearings to be placed further out from the center of the axle and closer to the frame this design is not only more robust and durable than the freewheel design, it is also typically much lighter. The cassette is usually a multi-piece unit and will most typically be like the cassette shown in the left-hand picture above (SRAM 970), comprising of a block of sprockets held together with a bolt (SRAM) or long rivets (Shimano). The two top (smallest) sprockets are separate pieces.

The XT cassette (second picture from the left), like the SRAM 990, has a 4 or 5 arm spider that the lower 5 gears are riveted to. The upper 4 gears are individual sprockets. This kind of design is much lighter than the traditional block design.

The freewheel mechanism for a cassette hub is contained within the freehub body of the rear wheel hub. The freehub body is splined to provide a good interface with the cassette. You’ll notice that one spline recess on the freehub body is broader than the rest, and that there is a corresponding broad spline on the cassette sprockets. These broad splines must be lined up before the sprockets can be mounted on the freehub. On a 9 speed freehub body, a 7 speed cassette will need a 5mm spacer. This is fitted before the rest of the gears (see the right-hand picture above).

On XT-type cassettes with individual sprockets, pay careful attention that you’re fitting them the correct way around. Each sprocket will have a number (eg. 14T, 15T) denoting how many teeth it has; the side with the number on should be facing out.

The cassette sprockets are then held in place using a lockring, tightened to 40Nm. The third picture above shows a lockring next to the fitting/removal tool.

Because the cassette is mounted to the freehub body it is not ordinarily possible to unscrew the lockring when it is correctly tightened. To enable us to remove the lockring we need to hold the cassette to prevent it from turning and for this job we use a chainwhip. It’s a great tool to have and although a good one will set you back £/$20-30 it really should be considered one of your ‘basic’ tools.

As per the pictures above, the chain whip should be fitted to one of the middle to large sprockets for best fitting and leverage. Even at the correct torque, a lockring should free up easily with a decent sized wrench. I favour a long handled chainwhip like Park’s SR-1 so that, in the eventuality of a jammed on lockring, I can rest the end of the handle on the tyre and hold it down with my weight under my knee, leaving me with both hands free to operate the lockring tool and wrench. Depending on how tight the lock-ring is fastened (or attached with rust/crud on a poorly maintained bike), there is a risk of the tool jumping out of the splines if you don’t keep the pressure on. I find that being able to push down with my left hand whilst turning the wrench with my right reduces the likelihood of this.

Once the cassette/freewheel is in your hands, it’s just a matter of getting the culmination of compacted lube and trail dust from the teeth and the spaces in between the sprockets. Bear in mind that if you clean your cassette whenever you clean/relube your chain it will be a much, much easier task. Various companies market long-brushed brushes for getting into sprocket clusters, but I find that a toothbrush/nailbrush and degreaser (Finish Line Citrus is my choice) does the job just fine. Whatever you use, a kettle full of boiling water should be used to rinse away all traces of degreaser before drying the gears thoroughly.

It’s possible, of course, to keep your rear gears in pretty good condition without removing them. The method that I use for cleaning my cassette after a ride is shown below. Although the pictures show the wheel out of the bike, this is only for clarity. This process works extremely well with the wheel still fitted, just make sure the bike is firmly propped up and unable to roll away from you. Of course, you will need to remove the chain.

Only if necessary, I’ll start by applying a small amount of degreaser to an old toothbrush and gently working it around the sprockets. You can hold a cloth directly over your scrubbing action to prevent the unavoidable spray that you’ll create. This’ll keep unwanted fluids away from disc brake components or rim braking surfaces.

My chosen lube (Purple Extreme) and application method means that I don’t usually have much dirt to clean off, but, regardless, here’s how I wipe down the sprockets…

  • Take hold of the cloth as shown and insert it between the first two sprockets.
  • With light pressure, pull the cloth up, wiping the sprockets as you go…
  • Now pull down in the reverse action, rotating the cassette on the freehub until you are back to the position you started at.
  • Repeat this cycle until the spaces between the sprockets are clean.
  • The sprocket teeth can be cleaned by covering a fingertip with your cloth and simply wiping the surfaces clean. This may seem like it’s going to take an eternity, but you’ll find that some teeth require very little effort. If you’ve kept a cassette maintained from new and chosen a clean chain lube, this task is usually fairly swift.

Back to main guide…

Written by SteveUK MTB

March 18, 2008 at 10:29 am

12 Responses

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  1. Your information is wonderfully helpful but I need help. I figured my hub was shot and tried taking it apart (not knowing anything about overhauling it.) I removed the nuts from the non-drive side and the cassette came off with the axle and exposed the inner workings of the freewheel (i.e. the pawls and the 1/16″ diameter bearings. There were 4 micro thin washers or spacers that came out of the center and appear to be worn out. Have I gone to the point of no return? Can I fix it? Can I remove the cassette from the outer part of the freewheel? Thanks.

    steve barbee

    July 23, 2009 at 1:36 pm

    • Hello Steve. Which hub do you have? Cassettes and freewheels are two different things, although from your description it sounds as though you have a freewheel (screws on rather than held on by a lock-ring). You can identify which is which from the pictures in the guide. It would really help to have some pictures of what you have in front of you, so it it’d probably be better if we took this onto the drivetrain forum at MTBR (forums.mtbr.com). It’ll be easier to work through it with you if there are pictures to go with your description, and you’ll also be open to draw upon the experiences of some more seasoned mechanics than I. If you don’t want to sign up for the forums, give me a shout back with as much info as possible and I’ll sort you out so that you can send me pictures…

      SteveUK MTB

      July 23, 2009 at 8:49 pm

  2. Hey,
    I would not call myself an intense MTBR, but I do enjoy going off the trails every now and then. How often should I clean these sprockets and how often should I lubricate?

    Kevin

    July 28, 2009 at 7:47 pm

  3. Hi,

    From one ride to the next my free-wheel hub seems to have failed. No warning leading up to it but yet soon after the pawls grabbed again…now I’m not sure if my problem was weather related (cold and wet prior to failure – once bike warmed up, free-wheel pawls grabbed again)or if I need a new free-wheel hub.

    It isn’t easy to get service but would rather not walk out of the forrest again.

    Advise please.

    Thanks,

    Howard

    Howard White

    December 29, 2009 at 1:32 pm

    • Hello Howard,

      It’s not uncommon for freehubs to break down during cold spells. Grease, especially old stuff, can harden and prevent proper action of the pawls/springs. A common trail-side cure is to take a piss on the gears to thaw the mechanism out out.

      Not exactly nice advice, but it’s the best I have for you.

      Steve

      SteveUK MTB

      December 29, 2009 at 3:46 pm

      • Hi Steve,

        Wish I had thought of that while in the woods! You did not suggest replacement as mandatory…I’ll give ‘er another shot and a good piss as needed.

        I like your holistic approach.

        Many thanks for the quick response.

        Howard

        Howard White

        December 29, 2009 at 3:50 pm

      • No problem at all Howard, I hope that it’s a simple solution for you. It’s not something that I have direct experience of, so I don’t know if breaking down in the cold is an indication of a hub in its final hours. Better than being caught out on the trail, perhaps you could leave the wheel outside over-night to see if you can replicate the problem and then test a possible solution? The obvious caveat is that your neighbours may start looking at you in strange ways, should you be observed…

        SteveUK MTB

        December 29, 2009 at 4:06 pm

      • No worries about the neighbors, they already think I’m crackers for riding bikes all winter long!

        Good suggestion – don’t know why I didn;t think of it.

        Thanks Steve,

        Howard

        Howard White

        December 29, 2009 at 4:56 pm

  4. I use the quick-release to hold the lockring removal tool in place while undoing it. Steve’s right – they often slip if you aren’t careful and you’ll damage your hand/spokes. I use a ring spanner rather than a socket – if you’re using a socket you may need a deep (long-reach) one to fit over the QR end – obviously not the lever end!

    Rick

    January 10, 2013 at 10:40 pm

  5. What is the plastic disc called that sits behind the rear gears? Thank you.

    Steven Norbury

    April 7, 2013 at 6:50 pm

    • I’ll be honest: I don’t know. Most people refer to it as a pie plate, though. It’s there to stop the chain damaging the spokes if it comes off the bottom (largest) gear. If the derailleur low-limit screw is correctly set, there is no need for the plastic disc.

      SteveUK MTB

      April 16, 2013 at 10:15 am

  6. Thanks so much for this guide. All of the other posts are awesome as well! Bookmarked for sure. My drive train has never looked as good as it does now. I messed up my brakes though, so if you have any info on bleeding hydraulic brakes that would be fantastic

    Ben

    November 12, 2013 at 6:08 pm


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