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I'm trying to find a good replacement for my MF-Z012 6 speed wind on cassette. Thing is, I've upgraded my bike with '93 Dura-Ace rear and front derailleurs. Trouble is they are 7-speed compatible. According to some digging I did, they might also work with 6-speed cassettes, but I'd like to play it safe and upgrade the cassette to 7 speed. Besides, not sure how great the old cassette's teeth are.

Also, I'd like to keep my original 6-speed Biopace crankset. Not sure if it's compatible with the Dura-Ace or with the 7speed cassette. I'm thinking it should be OK, since Dura-Ace also had a Biopace crankset version for the 7 and 8 speed groupset.

All advice is welcome.

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    The correct name for "wind on cassette" is threaded freewheel. Searching for that should find lots of information.
    – ojs
    Jul 28, 2016 at 13:51
  • Do you have Dura-ace shifters or friction shifters? Pre-97 dura ace derailleurs doesn't use normal Shimano cable pull, so you need dura ace shifters or friction shifters (which don't care about cable pull). Or a non-dura ace derailleur.
    – Batman
    Jul 28, 2016 at 16:19
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    As for finding a freewheel, 6 and 7 speed options are still around from companies like Sunrace, Shimano and IRD (in roughly ascending price/quality).
    – Batman
    Jul 28, 2016 at 16:22
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    6 speed freewheels tend to be 14-28 and good luck finding anything else. 7 speed freewheels have a little more scope, but tend to be mountain freewheels which may or may not suit. Its more to do with width than anything else - 6 and 7 speed are the same sized gears, so 7 speed is one gear wider physically.
    – Criggie ♦
    Jul 28, 2016 at 19:59
  • Right now, I have Shimano Exage Motion downtube shifters that have use both friction and indexing. As far as I saw on velobase, my model seems to be FD-7400 B. I don't want braze-on ones.
    – lorddarq
    Jul 28, 2016 at 20:13

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1984 – Shimano introduced Dura-Ace 7400 series with Shimano Index System (SIS) the first successful indexed-shifting system in cycling history. It was a 6-speed (7 and 8-speed later) system with indexed shifters mounted on the down tube.

From http://cycling-passion.com/dura-ace-history/

Your front mech is given as a FD7400B, which doesn't really carry a defined number of "speeds" because 6/7/8 all used roughly the same chain width. The B means it is a "band-on" fitting, not a F for "braze-on". It is rated for a big/small gap of 15 teeth.

Assuming your rear mech is from the same age, it will be a RD7400 which is rated for 6 speed and 26 tooth max cog. A RD7401 is a 6+7 mech and a RD7402 is an 8 speed mech.

The downside is that this generation of Dura Ace had a whacky cable pull ratio. So its ONLY compatible with a Dura Ace shifter of the same number of gears. You already have both.

The upshot of this is that you need a 6 speed freewheel, where the big cog is no bigger than a 26 tooth.

If you want more gears, you'll need a new wheel hub, cassette, rear mech, and right-hand shifter. Practically that means a replacement wheel. And your frame has to have enough width to take a wider wheel - the OLD on your 6 speed wheel might be 126mm and wider cassettes use more space. All that is covered in other questions on this site.

From Sheldon's site

Myth: Dura-Ace cassettes have a different spacing, and are incompatible with other derailers/shifters.

Truth: No, all Shimano cassettes and freehubs with the same number of speeds use the same spacing, and index with any system configured for the same number of sprockets.

You also need to avoid a freewheel with a bigger cog than 26 tooth. The top jockey wheel could impact the big cog and that's loud at best, and disastrous at worst.

There's some interesting info at https://www.sheldonbrown.com/dura-ace.html but you have the DA shifters and mechs, so that's not super-relevant to you.

Your biopace chainring won't care what you do at the backend. Front shifting might get a bit twitchy if you put a thin 11 speed chain through a front mech intended for 6 speed, but it just needs to be pushed over a bit more before the chain gets shoved. Easy.

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    If the right-side downtube shifter can be used in friction mode instead of indexed mode, just about any rear derailleur can be used. It's also not that hard to get a newer 10/11-speed wheel into a 126mm steel frame as you only need 2 mm on each side to get a 130 mm axle in. I'd be really careful about using an 10- or 11-speed chain on a crankset designed for a 6-speed chain, though. Such a chain might be narrow enough to squeeze into and get stuck in places that a 6-speed chain can't fit - like between the chainrings or between the outer chainring and the crank arm.
    – Andrew Henle
    Oct 12, 2018 at 13:10

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