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Replacing a single cog in a cassette?

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Replacing a single cog in a cassette?

Old 04-07-17, 09:49 AM
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deaninkl
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Replacing a single cog in a cassette?

A question for the knowledgeable here.. I have an 8 speed 12-26 cassette, I want to replace it with an 11-28 (Shimano HG51).. but I can't buy the HG51 locally here in Malaysia, I have found the cassette online but will take a month to get here... so.... could I take a 28 cog from another cassette, add it to my 12-26, take off the 12, and i'd still have a 8 speed.. as it is the low gear I'm looking for and am happy to give up the 12...

If for instance I took the 28T cog from a 11-32 9 speed cassette the chain size should not be an issue... or am I delirious here... just trying to overcome a very poor market for spare and parts, and taking into account that 8 speed cassettes are getting rare...

thank you.
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Old 04-07-17, 10:12 AM
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You may need to change your shifters (or go friction) to go from 8 speed to 9 speed.

You should be able to add a single 28T sprocket. You'll need a spacer too. If your cassette has several sprockets riveted together, you may need to separate them.

One problem that you'll run into is that the 11T and 12T sprockets are generally both designed to work as a first sprocket. However, the 13/14T is not, so you may have problems just dropping your 12T. Some first sprocket 13/14T are available, but that would be an extra part. Or, you could swap out something in the middle.

To go to an overall lower gear, can you use a smaller chainring?
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Old 04-07-17, 11:51 AM
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The smallest cog has a built in spacer that is required.
You could replace the 26T with the 28T however.
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Old 04-07-17, 12:22 PM
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Typically the largest 2-3 cogs are riveted together. You'd have to grind or file the rivets to separate the cogs.
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Old 04-07-17, 01:49 PM
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Can be done quite easily. If you drop the first position with the built in spacer you can put a spacer between the lock ring and the new first position sprocket. Can mean mucking about with spacers depending on the cassette to get it right.A ten speed spacer can be quite useful for this because it's thinner than an 8 speed.
Check the limit screws before you ride it.

Last edited by blamester; 04-07-17 at 01:51 PM. Reason: miss spelling
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Old 04-07-17, 04:03 PM
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Originally Posted by blamester View Post
Can be done quite easily. If you drop the first position with the built in spacer you can put a spacer between the lock ring and the new first position sprocket. Can mean mucking about with spacers depending on the cassette to get it right.A ten speed spacer can be quite useful for this because it's thinner than an 8 speed.
Check the limit screws before you ride it.
BULL!
The built in spacer part of the end cog is what engages the Free Hub splines.
Your method means the end cog will be jammed against the 2nd cog.
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Old 04-07-17, 07:42 PM
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Thanks for the answers gents, usefull to have this information. as I currently have no workshop I have gone the easier but longer route... and ordered an HG51 11-28 off eBay in the U.K., no express mail so it will take about 20-30 days to get here. But should work. That coupled with a compact crank (my bike came wing a (53/39) so now I have bought a 50/34.

Being inexperienced, and having a seller that just wanted to sell, I made the mistake of not researching, (I got a nice bike cheap, but it had a dated groupset with no spares locally). I'm 58, 30lb overweight and live in a very hilly area.... but the learning curve has been fun and the outlay to remedy things not too much, the frustration only is that I'm eager to have it all fitted and ready to ride..... kraut will go on today so tomorrow's hills should already be easier.

Thanks.
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Old 04-07-17, 09:18 PM
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HG51 Alivio 8 speed will work fine for you.

John
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Old 04-07-17, 10:05 PM
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Originally Posted by Bill Kapaun View Post
BULL!
The built in spacer part of the end cog is what engages the Free Hub splines.
Your method means the end cog will be jammed against the 2nd cog.
The number two also engages the splines with or without the spacer.
So you can use a spacer between the lockring and the cog so the lockring tightens against cassette and not the freehub and also a spacer on the other side just like every other cog. It's not impossible to do. Different sized spacers come in handy for this like i mentioned in the post.
I have a cassette where the first three have built in spacers and another where the number two is dished perhaps so they can use the same first position with different speed cassettes and different dishes on the number two.
So like i said it may only be a matter of mucking about with spacers to get the ratios you want.
And check the limit screws.

Last edited by blamester; 04-07-17 at 11:14 PM.
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Old 04-07-17, 11:11 PM
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I've removed the small cog and replaced it with a spacer. Actually I used spacers on both ends of the cassette to improve chainline slightly and when the person riding the bike will never have the chain on an 11t cog; starting with a 13t is fine. Once upon a time freewheels started with a 13t and had fewer cogs. Just removing it for the sake of not needing it would not be a good idea.

Only downside is the lack of serrations that are on the small cog for the lockring. So far I haven't had a problem after torquing the lockring.

John
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Old 04-08-17, 10:23 PM
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Yesterday I fitted a 50/34 compact crank, that is the first part of the equation, and wow what a difference on my hill this morning, it basically gave one and a half lower gears, this made all the difference, on parts of the hill I was previously having to get off and push I could get up the morning. 11-28 cassette should arrive at the end of April or early May... that should be the cherry on this fat riders cake.

thanks for the answers and great information.
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