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7 speed on a 9 speed hub...doable or not?

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7 speed on a 9 speed hub...doable or not?

Old 04-19-16, 05:25 PM
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bikenh
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7 speed on a 9 speed hub...doable or not?

Is it possible to put a 7 speed cassette on a 9 speed hub. I generally only ride one or two gears on a cassette so the shifting isn't much of a factor/worry. I'm just not sure if it's possible, using spacers, or if the gear spacing is bigger on a 7 speed and it would throw the shifting off making it next to impossible to ever get the chain to sit correctly on the cassette. Also I figure I would probably have to use a 7 speed chain versus a 9 speed chain...correct?

I have a friend of mine who has worn out his old 7 speed cassette, at least the 28 tooth cog, the rest of it looks great still. My 9 speed cassette is pretty much junk on the two gears that I typically use all the time and I figure since the teeth on his looks fine on those gears why not give it a shot...don't have anything to lose and maybe a few bucks to save.
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Old 04-19-16, 06:00 PM
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It's done all the time.

1. You need a 4.5 mm spacer to fit behind your 7-speed cassette.
2. You need 7-speed shifters because the indexing is different.
3. I'm pretty sure that a 9-speed chain would work but I'd use a 7-speed chain because they're cheaper.
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Old 04-20-16, 01:47 PM
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Other things to look for:

If you're adding this as a "new" wheel to an older frame the 7 speed hubs had 8 mm axles and the 8 and above had 9 mm axles so the wheel may not fit properly though usually there's enough play that they do.

The 7 speed hubs are spaced at 122 mm (from ancient memory) while the 9 speed are 128 mm. Older steel frames can be re-spaced by a competent shop. Do not attempt to ride it by forcing the wheels into the narrower yet flexible rear triangle because this will be slightly different each try.

Because of the required spacer you have to be careful that the limit screws on the rear derailleur are properly set because the chain jumping off inside can cut the spokes.
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Old 04-20-16, 02:49 PM
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Just the advantage in De-Dishing the wheel is lost. with the wider driver needed for a 9 speed cassette.

Correction: 6, 7_ 126, road 8 +is 130 MTB and My Rohloff is 135.

122 would be 5 speed or one.

My 6 speed freewheel hubs got a spacer on the left to 130 then I took out some drive side tension on the spokes .

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Old 04-20-16, 06:34 PM
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Originally Posted by Retro Grouch View Post
It's done all the time.

1. You need a 4.5 mm spacer to fit behind your 7-speed cassette.
This is what I did. Works fine with the 7-cog.
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Old 04-20-16, 07:26 PM
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Originally Posted by Retro Grouch View Post
2. You need 7-speed shifters because the indexing is different.
I knew there would be a real catch somewhere. Granted more than likely I would end up riding it single speed on the rear and just use the front for downshifting for climbs.

For everyone else, sorry about the 'late' reply but haven't been online since last night.

I'm planning on sticking with the same 9 speed wheel/hub combo and was just looking at using a 7 speed cassette on the 9 speed wheel.
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Old 04-20-16, 10:26 PM
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If your time is worth anything at all, a new ~$20 9-speed cassette is probably the cheapest option.
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Old 04-20-16, 10:40 PM
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Originally Posted by cyclintom View Post
Other things to look for:

If you're adding this as a "new" wheel to an older frame the 7 speed hubs had 8 mm axles and the 8 and above had 9 mm axles so the wheel may not fit properly though usually there's enough play that they do.

The 7 speed hubs are spaced at 122 mm (from ancient memory) while the 9 speed are 128 mm. Older steel frames can be re-spaced by a competent shop. Do not attempt to ride it by forcing the wheels into the narrower yet flexible rear triangle because this will be slightly different each try.

Because of the required spacer you have to be careful that the limit screws on the rear derailleur are properly set because the chain jumping off inside can cut the spokes.
If you read the OP's post, this is totally irrelevant, the OP states they have a 9 speed cassette, and are looking to replace with a 7 speed cassette. The only thing we don't know is if it's a road or MTB hub, and even then that's irrelevant as they aren't changing the hub, as all that is relevant is the use of the spacer as retro grouch notes.
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