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Restoring an old bike with smaller space between the dropouts and want to use it with a "modern" 9 speed XT derailleur. The shifting needs to be fluid so I'm trying to keep "9 speed" equipment (cogs thickness and spacing), because I'm worried that using 7 speed equipment would make everything clunky (chain jumping, gears not switching smoothly).

I need to save ~5mm so I would like to get a 9spd cassette or freewheel. How would you go at removing 2 cogs of a cassette or freewheel? The ones I look at seems to have the cogs "riveted"?

Thanks!

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    Sounds like this bike should be named after a Star Trek character, if you succeed.....
    – Criggie ♦
    Commented Apr 27, 2022 at 11:17

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If you buy a Shimano cassette, they are generally riveted and to free them you need to drill or grind the heads of the rivets off. SRAM and SunRace cassettes have a single long bolt you can unscrew or drill out to gain access to the individual sprocket. This applies only to the cheaper models in the line up where each sprocket is discrete. You will run into problems trying to do this with the cassettes that use a spider for some of the sprockets.

I have previously read that you can usually get 8 out of 9 onto a 7-speed cassette body but have never tried this myself, so please let us know how you get on.

Any Shimano Hyperglide cassette with 7 through 10 sprockets will fit any Shimano Hyperglide hub with the following exceptions:

  • 7-speed hubs only accept 7-speed cassettes --though 8 or 9 sprockets can be installed on a 7-speed hub, using 9- or 10-speed spacing. It is also possible to transplant an 8- 9- 10-speed cassette body onto most 7-speed Freehubs.
  • Dura-Ace 7800 and 7801 10-speed hubs (and Ultegra wheelsets) with the aluminum Freehub body and tall splines accept only Dura-Ace, Ultegra and 105 10-speed cassettes.
  • Many older hubs have a problem with 11 tooth sprockets. Capreo hubs and cassettes (special models with 9-tooth sprocket capability) are not interchangeable with anything else, though the 5 inner sprockets are interchangeable individually.
  • 11-speed cassettes will fit only 11-speed bodies, or Mavic's Shimano-compatible bodies.

https://sheldonbrown.com/k7.html

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  • Thanks Joek. If I get such a cassette, remove drill the rivets, remove the extra 2 cogs I don't want, how do I a re-assemble the cassette together before sliding it onto the hub?
    – tweedi
    Commented Apr 27, 2022 at 12:29
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    The torque of the lockring holds the cassette together, the rivets make packaging and fitting the cassette more convenient, they don't make a functional difference when you are pedaling. The cassette needs to overhang the freehub a little so the lockring can tensionthe cassette properly. If the lockring bottoms out on the freehub when you tighten it, you will need more space taken up. So try 8 of 9 on your 7 freehub as suggested. 7 of 9 without a packing spacer will almost certainly not allow you to tighten it up properly.
    – Noise
    Commented Apr 27, 2022 at 18:47
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If it's the 9 speed XT derailleur you want to use, it can work perfectly in an otherwise 7 speed drivetrain since Shimano derailleurs from 6 thru 9 speed mountain (and 10 speed road) all share the same actuation ratio. This means it will respond correctly to the 7 speed shifter input.

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  • Excellent idea although I have questions: According to Sheldon Brown website 7 speeds cassettes or freewheel have thicker cogs and a different spacing. Will the derailleur still shift smoothly with this in mind? Another consideration: I still have a crankset with 3 chain rings at the front, therefore that would be 3 chain rings front, 7 speeds freewheel, 9 speeds derailleur, will any chain fit this?
    – tweedi
    Commented Apr 27, 2022 at 12:27
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    The shifter controls the derailleur movement. So a 7 speed shifter will move the derailleur the required 7 speed spacing. I would try a 7 speed chain. The cage of the 9 speed derailleur is a bit narrower than a 7 speed s would be. If you suffer chain rub there go ahead and move to a 9 speed chain which will work with very little risk of problems.
    – Jeff
    Commented Apr 27, 2022 at 13:27
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    I doubt you'll experience any problems using a 7 speed chain
    – Jeff
    Commented Apr 27, 2022 at 13:28
  • Thanks for your messages. I think this is what I will try first. Regarding the shifters could I keep my 9 speed shifters shimano SLX with the 9 speed XT derailleur, and the 7 speed cassette? Just means I won't use the full range right?
    – tweedi
    Commented Apr 27, 2022 at 21:18
  • The 9 speed shifters shift a derailleur (having the correct actuation ratio) 9 speed spacing. Thus, with a 7 speed cassette/FW with different spacing than a 9 speed's, shifting will be off. Definitely not the "fluid" you seek.
    – Jeff
    Commented Apr 29, 2022 at 6:52
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I don't know about 9 speed, but you might be able to make this work using 10 speed parts. Some (all?) 10 speed Shimano cassettes come with the the top 3 sprockets as one unit and then 7 loose sprockets. There is an exploded diagram in this document: Shimano 10 speed cassette

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Assuming your frame has an 130mm OLD spacing because it was 7 speed originally - it may be reasonable to "stretch" the frame.

This requires a steel frame if your bike has aluminium or carbon fibre or titanium or wood or anything other than steel, this cannot be safely done.

The basic method is simple but brutal. You use leverage through the rear triangle and braced against the seat tube or a stringer that will protect the frame and spread the load. A 2-3 metre length of 4"x2" construction timber makes an adequate lever. Simply alternate sides of the frame until the OLD matches what you need for your 9 speed wheel.

Then you need to tweak the dropouts so they are still parallel. Skipping this means the wheel's nuts/QR won't sit square and will walk itself out of the dropouts over time.

Brakes should be unaffected by this stretching, and need no more tweaking than any other wheel swap. Pad alignment and closure gap is about all.

5mm is about the maximum a steel frame can be adjusted. That would be 126mm up to the next standard size of 130, or 130 to 135. You would not succeed in going 126-->135 because of excess stresses on the welds and brake bridge etc. I've personally done it on a steel MTB and the resulting bike went from 3x5 speed to 3x9 speed, and I still ride it 8 years later.

The front fork will almost always be 100mm OLD, and should not need modification at all.

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    This answer provides an alternative solution that addresses the underlying need, but not the question-as-asked.
    – Criggie ♦
    Commented Apr 27, 2022 at 11:16
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    Thanks for suggesting this. I had tought of cold setting but indeed I have an aluminium frame, and you're right, it's a 130 mm dropouts.
    – tweedi
    Commented Apr 27, 2022 at 12:24
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You don't remove 2 cogs. You remove 1 cog.

That's called "8 of 9 on 7".

9-speed cogs are thinner. If you take seven 9-speed cogs, you have a far thinner cassette than a typical 7-speed cassette. However, if you take eight 9-speed cogs, you have a cassette that's approximately the width of a 7-speed cassette.

You'll break the Hyperglide mechanism though but that's to be expected. People rode without Hyperglide for ages and nobody complained.

You also have to use a 9-speed shifter, but one of the clicks will be "empty" then. You should make that "empty" click the largest gear, so the two largest gears would be at the high limit derailleur screw.

Those rivets will be removable with an angle grinder or Dremel. There may also be cassettes that have screws instead of rivets, but those were the expensive cassettes and may not anymore be available for 9-speed since nobody reasonable would ever ride without 12-speeds so let's extract money out of unsuspecting cyclists by starting to sell 12-speed gear!

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