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Old 07-23-08, 01:00 PM   #1
bryroth
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What is reduced cog spacing?

I found a good deal on a new 9-speed cassette. Says it has "reduced cog spacing" and that it is the same width as an 8-speed. Will it still work with my 9-speed brifters?
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Old 07-23-08, 01:17 PM   #2
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If it's a Shimano-compatible cassette, and you have a Shimano-equipped bike, it'll fit and work just fine.

When 9-speed was the new thing, all the ads touted "reduced cog spacing," meaning you could upgrade
your 8-speed bike with new deraillers, shifters, and cassette, but you could keep your existing rear wheel.

No innovation is painless, though... since there's less space between cogs, 9-speed bikes have to run a narrower chain that 6-7-8 speed.

I'd imagine that all you're trying to do is replace a worn-out 9-speed cassette without taking out a second mortgage to buy Ultegra or Dura-Ace, and you're wanting to try a Performance or Nashbar brand cassette.
It's a little heavier than the "good stuff," but it'll work as advertised. I've had a cheapo Performance one on
my 1999 Specialized Crossroads going on 20K miles now, and it still has all its teeth...

Go for it.
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Old 07-23-08, 01:21 PM   #3
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Actually upgrading from 7-speed Sora. So far I've bought the new 9-speed shifters (Tiagra). My RD should still work if I understand correctly. This will take care of the cassette.

Do I need a new rear wheel, based on what you said above?
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Old 07-23-08, 01:48 PM   #4
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Yep, 'fraid so.

The 7-speed cassette is narrower than the 9-speed. You can put a 7-speed cassette on a new wheel, with a 4.5mm spacer, but you can't put a 9-speed cassette on an older wheel.

Sora... are you certain that it's 7-speed? Unless the bike is dog's years old, it could be Sora-8. (If you counted the cogs, then I stand corrected.)

The RD should be okay with the Tiagra shifters. Reserve some time for much tweaking.

Good luck.
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Old 07-23-08, 01:54 PM   #5
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There are 7 cogs, but it's not old. Maybe there's a spacer? And if that's the case then I would actually NEED the reduced cog spacing in order to use 9 gears but still keep the wheel. Correct?

What does a spacer look like? Is it behind the big cog or the small cog?
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Old 07-23-08, 02:50 PM   #6
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Originally Posted by bryroth View Post
There are 7 cogs, but it's not old. Maybe there's a spacer? And if that's the case then I would actually NEED the reduced cog spacing in order to use 9 gears but still keep the wheel. Correct?

What does a spacer look like? Is it behind the big cog or the small cog?
The spacer would be about 4.5mm thick and located behind the cassette (between the largest cog and the spokes); it'd be hard to miss. If there is a spacer, then that freehub would be compatible with 8-, 9-, or 10-speed cassettes. Freehubs can be transplanted though. This all assumes you have a cassette, and not a freewheel system.

8-, 9-, and 10-speed road wheels are usually spaced 130mm (vs 126mm for 6- and 7-speed). You may need to spread your frame (hope it's steel) if replacing a 7-speed freehub with an 8-speed-plus freehub.
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Old 07-23-08, 04:02 PM   #7
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You guys are awesome, thanks for the help. That reduced cog spacing sounds like what I need. I just need to get the right chain to go with it.
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Old 07-23-08, 04:12 PM   #8
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You guys are awesome, thanks for the help. That reduced cog spacing sounds like what I need. I just need to get the right chain to go with it.
Forget about the whole "reduced cog spacing" jargon. It's just marketing. When it comes to Shimano-compatible cassettes, 8-speed is 8-speed, 9-speed is 9-speed, etc. Match the speeds of your rear shifter, cassette, and chain and call it good.
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