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Old 09-02-07, 08:00 PM   #1
doctor j
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Cogs from Two Cassettes?

I posted this over in the mechanics area and got one reply which was helpful. I would like opinions/advice from my brothers and sisters here at 50+

My road bike has an 8-speed Sora triple drive train. I had the original equipment 12-24 cassette changed to a SRAM 11-28 for a century with a good bit of climbing, allegedly 6,300'+. The original cassette is in good shape. The original equipment cogs are: 12, 13, 14, 15, 16, 18, 21, 24. The new cogs are: 11, 12, 14, 16, 18, 21, 24, 28.

I've been training with the new cassette, and it appears that, for me, the 11-tooth cog is a bit too much. One the other end, the 28-tooth cog is great for hills > or = 10%

Is there any mechanical reason that I could not have the 11-tooth cog removed from the new cassette and replace it, in the proper size order of course, with either the 13-tooth or the 15-tooth cog from the old cassette?

Thanks for any assistance.
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Old 09-02-07, 08:26 PM   #2
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Sounds like it would work as long as the 12 and 13 cog is a free by itself cog. It's a simple enough thing to do if you have the cassette lock ring tool. +1 on the 28 cog. I changed to a 11 x 32 cassette for hill climbing; although also had to change dérailleur.
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Old 09-02-07, 09:12 PM   #3
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On all four of my 8-speed cassettes, only the two smallest gears are separate. The other six are in a cluster. If it's the same with yours, which is likely, you can swap the 11 & 12 for the 12 & 13. To get rid of the 11, you'll have to switch both of the two smallest gears for reasons that will become apparent as soon as you remove the cassette.

It sounds like you're going to hire this done. For about $11 at Nashbar, you can buy the tools required--a cassette lockring tool and a chainwhip. It's actually easier (and faster) than fixing a flat. Give it a try yourself.

Once you do, you may end up like I did, owning multiple cassettes, each appropriate to specific riding conditions. On my Sora road bike, I run a 13-23 around town and a 12-28 in the hills. On my Alivio hybrid, I run a 12-23 on the canal paths, and an 11-32 when fireroading.
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Old 09-03-07, 03:05 AM   #4
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You may on certain brands of cassettes also need to change the lockring as it can be "tooth specific".

If you are of a mind to, you can take the "carrier" apart and mix and match the lower gears as well. On many carriers, the lower cluster is held together by long screws or bolts or even rivits that can be carefully drilled out. Keep everything in some sembalance of order while you sort through it. The spacers between the gears are "speed" specific, ie 8 speed spacers are one thickness, 9 speed another etc.

There will be families of gears that you will get better results with (example...Shimano HG50) because the shifting details (ramps and climbing areas) will line up with adjacent gears but experimentation may produce some interesting results.

The gears do not need to be bolted back together in the cluster as they will retain their positions via the splines.

There are some good articles on this in the Sheldon Brown series along with his nifty gearing calculator.
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Old 09-03-07, 06:43 AM   #5
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If you do swap and go with the 12T, you'll probably want to use the lockring that came with the 12. If memory serves me (remember this is a 50+ forum!), there is something different about an 11 or 12 tooth cog that requires a different lockring for each (something about an 11 is dif). At least when I changed over my mtn. bike cassette, I read something about the 11T cog requiring a dif. lockring.
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Old 09-03-07, 07:02 AM   #6
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Quote:
Originally Posted by maddmaxx View Post
..The spacers between the gears are "speed" specific, ie 8 speed spacers are one thickness, 9 speed another etc...
Thanks Madd, I think you just fixed a shifting problem I've been having.
I cleaned & regreased the bearings, etc. on my rear wheel and in the
process replaced a cracked plastic spacer. I bet I accidentally put an
8 speed spacer in my 9 speed cassette. I was wondering why the
rear derailler suddenly wouldn't adjust.
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