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Dura Ace 7900 Larger Cassette

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Dura Ace 7900 Larger Cassette

Old 05-17-20, 11:36 PM
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Champ340
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Dura Ace 7900 Larger Cassette

Hey guys,

I have a Dura Ace 7900 groupset with 11-28 cassette. I would like to run a larger cassette because where I live is very hilly. Up front is 34/50. I am happy to buy another rear derailleur that can accommodate the larger cassette but don't want to replace entire groupset.

Does anyone have any options or workarounds available for me? Thanks alot.
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Old 05-18-20, 06:33 AM
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shelbyfv
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I used a 30T with a 7900 rear derailleur, worked fine. IIRC, there may have been clearance for a 32. As you know, it depends on your frame. I needed a 32 on another 10 speed bike and used a 9 speed mtb derailleur.
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Old 05-18-20, 06:37 AM
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The Deore M591 9 speed MTB rear derailleur will get you up to a 34t cog in the rear. They work fine with 10 speed road shifters.
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Old 05-18-20, 11:02 AM
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I've never tried one of these, and didn't even know they existed.
But it's worth the read.

All the best

Barry

OH, BTW, I just went through a similar change with an Ultegra 6700. You can read about it here.

Last edited by Barry2; 05-18-20 at 11:06 AM.
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Old 05-18-20, 05:17 PM
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I love pointing my bike straight up hill. I'm currently running 12-30 x 50-34 and it is just enough. If you went 12-32 or 11-32, I'd imagine it you'd never ask for more - unless loaded.

For that, I would try adjusting the b-screw or even getting a longer one. You don't need to get it to go much more.

The wolf tooth will work but is probably more for going 11-36. Unless you're off road, I can't imagine needing it.

Make sure you have plenty of chain when first adjusting it. It's pretty easy to forget and crunch it even in a workstand.

If you do need a new rear derailleur, I have a 10 speed XT that handles 42 teeth just fine. It's nearly new, I just like Shadow Plus better. I'll make you a screaming deal. I don't know if 10 speed road and mountain are compatible though.

Last edited by rosefarts; 05-18-20 at 05:20 PM.
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Old 05-19-20, 01:13 AM
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Thanks Barry for the link to your thread that was very helpful. And thank you everyone else for the replies. I am thinking of getting the 105 RD-5701-GS 10 speed. It is medium cage so can handle a 32 Cog. I have found a couple on eBay.

Can anyone see any issues with pairing this with the Dura Ace 7900? From the compatibility charts I have seen it should work no worries.
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Old 05-19-20, 10:57 AM
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For several years I’ve been using a 7900 short cage rear derailleur with a 32t cassette on several of my bikes with no modifications. If you do this you will have to have a longer chain sized for the big/big combo.
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Old 05-19-20, 12:26 PM
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Originally Posted by Champ340 View Post
Thanks Barry for the link to your thread that was very helpful. And thank you everyone else for the replies. I am thinking of getting the 105 RD-5701-GS 10 speed. It is medium cage so can handle a 32 Cog. I have found a couple on eBay.

Can anyone see any issues with pairing this with the Dura Ace 7900? From the compatibility charts I have seen it should work no worries.
Check what you can find a 105 RD-5800 GS for. Then you can run it with your 10 speed cassette and be ready for 11 speeds just in case you might want to upgrade shifters and get another cassette at some point in the future.

I think the travel of the DR is the same as an equal amount of pull on the 10 speed DR. It's only the shifters that change up the amount of pull. But someone should double check, I might be thinking wrong.
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Old 05-19-20, 12:45 PM
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Originally Posted by Iride01 View Post
Check what you can find a 105 RD-5800 GS for. Then you can run it with your 10 speed cassette and be ready for 11 speeds just in case you might want to upgrade shifters and get another cassette at some point in the future.

I think the travel of the DR is the same as an equal amount of pull on the 10 speed DR. It's only the shifters that change up the amount of pull. But someone should double check, I might be thinking wrong.
the pull of the 11-speed 5800 rear derailleur is different than that of 10-speed and not compatible.
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