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Which rear gear for STI 8's?

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Which rear gear for STI 8's?

Old 12-02-21, 07:36 AM
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clubman 
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Which rear gear for STI 8's?

I've been asked to fix a weather beaten Korean bike with an 8 speed STI drivetrain. The owner is struggling with money so I'm trying to do it cheap. His derailleur was sucked into the spokes and trashed and I've replaced the bent hanger but I don't have any specific 8 speed gears in my stash.
Can I use a Deore M730 or any other similar generation Shimano RD as a replacement? TIA
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Old 12-02-21, 10:43 AM
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Originally Posted by clubman View Post
I've been asked to fix a weather beaten Korean bike with an 8 speed STI drivetrain. The owner is struggling with money so I'm trying to do it cheap. His derailleur was sucked into the spokes and trashed and I've replaced the bent hanger but I don't have any specific 8 speed gears in my stash.
Can I use a Deore M730 or any other similar generation Shimano RD as a replacement? TIA
Wouldn't a current generation Altus work? Those are like $20-30 USD new.
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Old 12-02-21, 10:48 AM
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Well Altus would work except they're $44 cdn at the lbs and I'm really trying to keep the tab down. This guy has a family of 6, one income, big rent etc. By the time I replace the chain, hanger, cables, brake pads, a tube/tire, it's going to hurt so if I can donate a gear to him, I'll do it.
Any opinions are appreciated.
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Old 12-02-21, 10:56 AM
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Russ Roth
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Any SIS 7-9sp non-Dura Ace rear der will work. an 8sp der would work the best but any of them will work fine. MTN or road doesn't matter.
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Old 12-02-21, 11:31 AM
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Much appreciated.
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Old 12-02-21, 03:27 PM
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Originally Posted by clubman View Post
Well Altus would work except they're $44 cdn at the lbs and I'm really trying to keep the tab down. This guy has a family of 6, one income, big rent etc. By the time I replace the chain, hanger, cables, brake pads, a tube/tire, it's going to hurt so if I can donate a gear to him, I'll do it.
Any opinions are appreciated.

I misunderstood the question and thought you meant you didn't have one. If you have that on hand, like Russ Roth said, it should work.

Good on you for doing this.
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Old 12-02-21, 05:18 PM
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The M 730 should work fine but you will be limited to 13 on the small cog and 30 on the big for good shifting likely not a big deal.
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Old 12-20-21, 06:36 PM
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Originally Posted by zukahn1 View Post
The M 730 should work fine but you will be limited to 13 on the small cog and 30 on the big for good shifting likely not a big deal.
What? 34 teeth is the max cog on this derailleur. As well, it has the same exact geometry as the same generation of DX. I've used the DX (and LX) on 13-34, 11-32, and 12-28 cassettes. I'm just not understanding why you're stating those limits
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Old 12-24-21, 02:50 AM
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Originally Posted by Russ Roth View Post
Any SIS 7-9sp non-Dura Ace rear der will work. an 8sp der would work the best but any of them will work fine. MTN or road doesn't matter.
More costly to come by perhaps, but I would think a 10sp RD would work as well.
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Old 12-25-21, 12:49 PM
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Originally Posted by jccaclimber View Post
More costly to come by perhaps, but I would think a 10sp RD would work as well.
Less likely to work. The number of 10sp rear derailleurs that will work with 8sp shifting is limited and most won't. Even the few that will won't work as well due to the narrower cage vs the wider chain.
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Old 12-25-21, 01:24 PM
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The 7700 DA works. But that Deore would be perfect.
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Old 01-04-22, 12:07 AM
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Just run the M730.

As for minimum size cog, I’ve never heard of a good explanation, or an instance, where an older RD wouldn’t shift with an 11t or a 12t cog when Shimano’s minimum was 13t.

I’ve often thought the minimum cog corresponded to what Shimano had available in the correct group (road or mountain) at the time and not on the inability of the RD to function.

The RD-M730 SIS 6 speed came out in 1987. The only 12t Uniglide freewheel/cassette I am aware of in 1987 was Dura Ace. Shimano wouldn’t recommend a road freewheel/cassette for a mtb application.

John
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Old 01-05-22, 09:38 AM
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Originally Posted by clubman View Post
I've been asked to fix a weather beaten Korean bike with an 8 speed STI drivetrain. The owner is struggling with money so I'm trying to do it cheap. His derailleur was sucked into the spokes and trashed and I've replaced the bent hanger but I don't have any specific 8 speed gears in my stash.
Can I use a Deore M730 or any other similar generation Shimano RD as a replacement? TIA

It's been a month and this thread just got bumped. Did you try to install the M730?
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Old 01-05-22, 10:23 AM
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Originally Posted by livedarklions View Post
It's been a month and this thread just got bumped. Did you try to install the M730?
Thanks for asking. I did, but it's not able to travel the full width of the cassette. It's making me crazy and I've adjusted most everything...chain length, the limit screws, B screw, new cables, even bought a new hanger. It's been on the back burner for the holidays but I'm going to try yet another derailleur and then flush the shifters in a last ditch attempt. May have to spring for a new Altus in the end. Ideas welcome.
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Old 01-06-22, 02:34 AM
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Originally Posted by clubman View Post
Thanks for asking. I did, but it's not able to travel the full width of the cassette. It's making me crazy and I've adjusted most everything...chain length, the limit screws, B screw, new cables, even bought a new hanger. It's been on the back burner for the holidays but I'm going to try yet another derailleur and then flush the shifters in a last ditch attempt. May have to spring for a new Altus in the end. Ideas welcome.
Sitting in the wrong gear when you secured the cable? Disconnect the cable and see if it travels across all rear sprockets when pushed by hand. Also verify the limit screws are out, not in.
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