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Nine speed cassettes (rear cog set) for your bicycle are not prohibitively expensive, but it would be nice to get a few hundred or more additional trouble free miles from them. A particular pattern of wear caused by the chain on the cog teeth creates problems that show themselves as chain skipping or hopping and poor shifting or hesitations in the movement of the chain from one cog to the next during shifting.

Pictured below is the profile of the gullet between two teeth on a typical cog.

Step 1: The Hook

Over time and use, a hook wears into the gullet profile as shown by the red color. This keeps the chain from sliding out of the gullet smoothly on every tooth during use. This hook does not need to be very pronounced for it to affect performance.

Step 2: Check for Hooking Wear

To check for the presence of hooks on your cog teeth, slide your fingernail from low in the gullet along the working edge of a cog tooth and see if your finger slides effortlessly off of the tooth or if you feel it catch a little on a hooked indentation near the top of the tooth.

Step 3: Grind Away the Hooks

You can lightly grind away the hooked portion of the cog tooth and your gear train will work better than it has for a while.

It is generally not good practice to grind from the side of an abrasive wheel, but you are removing so little material that there is no risk. You are not grinding at the bottom of the gullet. Doing so might result in uneven fit of the chain on the cog teeth. Just touch the teeth to the wheel for a second or two and move on to the next tooth.

Each cog is stamped with the number of teeth on that cog. In order to stay aware of your progress, check the number and count as you finish each tooth. You will easily know when you have finished.

I have obviously removed the rivets that hold most clusters together. To remove the rivets, lightly grind the heads away from the smallest cog. Use a nail as a punch and tap a couple of light taps to push the head out enough to get a plier onto it. Pull and twist carefully to remove the rivet. The spacers between the cogs are plastic. I learned from experience that driving the rivets out the entire way with a nail can crack the plastic spacers. Removing the rivets makes cleaning the cluster much easier. Soak in a cleaning solution and wipe, or just wipe each cog and each spacer with a rag. Be careful to remove all of the road grit. If it gets between the cogs and the spacers, there will not be enough room on the spline for all of the cogs.

Step 4: Cassette Removal

As you likely know, you need a special cassette removal tool to remove the locking ring. Once it is off, the cassette and its cogs slide off of the end of the spline. Cassette removal tools are specific to the maker of your cassette. A bike from Wal-Mart does not use the same removal tool as a bike with Shimano parts, etc. Check the web site for Park Tool.

Step 5: Assemble the Cluster

The spacers will fit onto the spline a couple of different ways. They should slide on with ease. Do not force them. The cogs will go onto the spline only one way. When the spline and a cog are properly aligned, the cog slides on with ease. The cogs will not fit if they are wrong side up.

When all cogs and spacers are on in their proper order, thread the locking ring onto the spline's end and tighten well with a big wrench.

Grinding the hooks from worn cogs helps performance and extends cassette longevity. But, if your chain is worn beyond its tolerance, or the derailleurs are not properly adjusted, or the chain has a tight link you will still have chain skip or hopping and shifting problems. If you do not know how to adjust your derailleur, there are Instructables on doing that as well as tutorials various places on the Internet. Some bicycle owner's manuals include a detailed procedure for derailleur adjustment, too.

There is a practical limit to how many times you can grind the hooks from the cogs, but it is still worth the effort at least once or twice.
<p>On reversing sprockets: As you can see in the photos, modern cogs have ramps on the faces of them to help the chain climb from the smaller to the larger ones, also the ends of the teeth are angled to make them shift easier as well. So flipping them over results in poor shifting.</p><p>The wear this 'ible addresses is due to a worn-out chain, though this is colloquially called &quot;stretch&quot; it is actually due to wear in the pins and plates (or bushings in older, wider chain) rather than actual stretching. Chains should be replaced at 1/2% stretch, and if allowed to get to 1% then the sprockets need replacing as well.</p><p>Cleaning the chain by removing from bike and immersion in solvent, drying, and then re-lubing with non-detergent oil, or gear oil will provide decent chain life.</p><p>If you count off 10 full links (20 half links) there should be 10&quot; between the pins at the ends. If it is 10.05, then the chain needs replacing, and if it is 10.1&quot; or more, then not only is the chain worn out, but it has almost certainly done damage to the sprockets as well. </p><p>Note that 10-1/16&quot; and 10-1/8&quot; are plenty close enough to the figures above. A decent ruler will do, no need for a fancy caliper. Bike shops have a purpose built gauge that makes it a lot more likely you will keep tabs on your chain wear.</p><p>Also, if you refrain from shifting under load, then the hooking doesn't impede shifting much. Prior to the ramps and twisted teeth, shifting under load didn't work for diddly, so the notion that you can (much less, should) is pretty modern.</p>
<p>If there was a way to mount the cogs from the other direction it would double its life (i guess some brands you can). In this image it appears the inner holes wont line up so needs six extra holes each. Line two cogs up, clamp, centre-punch through the top one, seperate and drill. 9*6=54 holes. Perhaps easier than trimming all those teeth.</p>
The cogs are keyed so they can go on only one way.
Heh Phil. I'm only familiar with one type of cassette, the shimano m760 9 speed and the rivet heads on outer side are flat with cog(so you would have to also grind cog face) and on the inner spoke side most heads are visible but indented into plastic spider so can't reach with grinder. Wondering what kind of cassette you have and/or how you do this rivet removal. Also, are you saying you only have to remove the small cog rivets? Not on mine. <br> <br>Would sure like to try this and get more life out of cogs. Thanks for the excellent post. <br> <br> <br>
Thank you for your comment and inquiry. It has been a couple of years since I did this last. The cassette was stock from the factory on my 2006 Specialized Allez Sport triple (27 speeds--9 speed cassette--Shimano equipped). I do not have the model number of the cassette. As I remember, the rivet heads on the spoke side were round rather than flat. I did not find the plastic spider you mention. I think I got a couple hundred extra miles out of my old cassette by grinding the hooked teeth on my old cassette. This does not give an unlimited life extension. I think this fix was worthwhile, but I also remember that when it was really, really time for a new cassette, the new cassette was a very nice improvement.
Yes, I have since learned that not all cassettes have the spider that blocks rivet head access that my XT unit has. Just saw a Sram PG970 9 speed that has a very small 1.5mm allen head screw on back that allows individual cog removal. I'm surprised you only got a couple hundred miles.
if you take the hooks off wont it work even worse
No. The hooks interfere with the smooth release of the chain from the cog teeth.
If the cassette rings are symmetrical, you might be able to double their life simply by flipping them over. Can you think of problems with that?
Your idea is clever and makes good sense. But, the experience I had in putting the cogs back on the spline is that they will not go onto the spline if they are wrong side up, that is flipped. They will go on only in their factory ordained position. Thanks for the suggestion, though.
I understand what you are saying, or, they say in the South, "I hear ya'." I biked a lot in my 20's and some in my 30's. Then I began to think I was too busy. I jogged, but eventually I tired of that. The weight began to accumulate around my middle. 28 months ago I decided no one was going to do it for me, so I began riding. It puts me into a mellow state of mind when I am out on the bike. I have racked up 7,000 miles since and try for 100+ miles per week. My "new" bike (parts shown here) now has 5,000 miles on it. Find a route you like or a time of the day when you can ride a route you like without too much traffic, and ride for enjoyment. The health benefits will come with it.
I look forward to the day I have to replace parts due to too much usage. Nice 'ible, thanks for the info!

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