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Old 02-24-07, 11:22 PM   #1
aikigreg
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7-9 speed compatibility

I have a bike in need of a new crankset and cassette. The bike is currently a 7 speed. I am upgrading to a 8 speed cassette since I know the chain can handle it, but I also wanted to uy a new crankset. The crankset I want to buy says 9-speed. Any problems using a 9-speed crankset with a 8-speed chain?
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Old 02-24-07, 11:24 PM   #2
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Shimano I presume? Go to Sheldon Brown's website and look for compatibility issues.
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Old 02-24-07, 11:29 PM   #3
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yes, shimano. I've been all over sheldon's website -I can never find a darned thing there. His links for cranks are very light on info. I can't find anything on compatibility at all.
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Old 02-24-07, 11:50 PM   #4
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Originally Posted by aikigreg
yes, shimano. I've been all over sheldon's website -I can never find a darned thing there. His links for cranks are very light on info. I can't find anything on compatibility at all.
It's there somewhere. His basic point, if I recall correctly, is that cranks and chainrings don't care much about speeds. I have run 9 sp chain on a 7 sp crank with no issues. What you want to do should be fine - at least as far a the crankset is concerned. Shifter/hub/derailleur/cassette compatibility is another question. I could be wrong, but I didn't think that Shimano 8 speed cassettes would fit on a 7speed freehub.
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Old 02-25-07, 12:12 AM   #5
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Originally Posted by aikigreg
I have a bike in need of a new crankset and cassette. The bike is currently a 7 speed. I am upgrading to a 8 speed cassette since I know the chain can handle it, but I also wanted to uy a new crankset. The crankset I want to buy says 9-speed. Any problems using a 9-speed crankset with a 8-speed chain?
no
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Old 02-25-07, 04:08 AM   #6
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Quote:
Originally Posted by aikigreg
I have a bike in need of a new crankset and cassette. The bike is currently a 7 speed. I am upgrading to a 8 speed cassette since I know the chain can handle it, but I also wanted to uy a new crankset. The crankset I want to buy says 9-speed. Any problems using a 9-speed crankset with a 8-speed chain?
No, there shouldn't be any problems.

As far as Campy or Shimano goes 5-9 sp cranks are really the same. Most, but not all, 5-7 sp cranks aren't ramped or don't have the pins. These were designed to aid in moving the narrower 9 sp chain. Most 10 sp specific cranks have the chainrings closer in addition to being ramped and pinned.

Good luck

Tim
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Old 02-25-07, 08:33 AM   #7
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sheldon brown's article on shimano compatibility

Here's what you want. For chainrings, the width/thickness for different speeds are the same as the cassette sprockets in his table. You will notice a shifting difference if you try to run a narrower chain than chainwheel, eg. a 9 speed chain on an 8 speed chainwheel. Not so much the other way around. The crankset is not important, the rings are.

Last edited by vpiuva; 02-25-07 at 08:39 AM.
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Old 02-25-07, 11:44 AM   #8
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If you are going to change the cassette, by all means change the chain too. Going to 8-speed instead of 9, just because your current chain will work is the wrong kind of economy.

Chains wear quickly and a new cassette with a worn chain is a sure recipe for skipping. The chain is the least expensive component available. Get a new one.
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Old 02-25-07, 07:46 PM   #9
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Thanks y'all! That link was just what I needed, Vpiuva.

Hillrider - it's a recumbent and a brand new chain, so I don't feel like spending the $$$ to chain that as well, and am not bothered by 9 or 8 speed, but since I'm buying new stuff anyway I figured I'd try and squeeze a bit extra hillclimbing ability into it.
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