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Shimano Dura Ace RD-7900 Rear Derailleur

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Item # SHI0150

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Item # SHI0150


Shimano's dominant position in the bike industry is based foremost on one simple fact: They can forge metals with a creativity and sophistication far beyond anything their competitors can dream. Shimano factories are crammed with VW Bug-sized forging machines that spend all day long pounding alloys into highly precise little bits that -- after final assembly -- make a Dura-Ace bike brake and shift and look so fine.

Shimano = Forging. It's as simple as that, and that's the reason why they long resisted the temptation to wander into the world of carbon. The rest of the industry, of course, embraced carbon with an untrammeled cheek-to-cheek, two-arms-and-two-legs enthusiasm, and while they were at it, they accused Shimano of being a fuddy-duudy for not doing the same. Shimano's position was simple: Anything carbon can do, forged metal can do better -- lightness, durability, cost, you name it.

Still, there's something cosmetically sexy about carbon. And market trends are what they are -- consumers vote with their wallets, and they're choosing carbon. With the Dura-Ace 7900 series components, Shimano proves that while they may move deliberately, they are most definitely not fuddy-duddies. Case in point, the Dura-Ace RD-7900 rear derailleur --

The Dura-Ace RD-7900 is Shimano's first ever rear derailleur that makes use of carbon fiber. The pulley cage and P-body are both made of carbon to shave off 16g in comparison to the RD-7800 rear derailleur. Shimano states that their choice of carbon vs. alloy here has no detrimental effect to long-term durability of the derailleur.

And while the carbon vs. alloy debate has a timelessness to it akin to Red Sox vs. Yankees, there's something else going on with the RD-7900 that -- at least to us -- is far bigger news: It has an expanded chain wrap capacity in comparison to the RD-7800. What's chain wrap capacity? It's a simple math equation: (Big ring - Small ring) + (Big cog - Small cog) = Chain Wrap Capacity. Other rear derailleurs have limitations that prevent you from the big wrap values that come from choosing, say, a 50/34 crankset and a 12/27 cassette. The Dura-Ace RD-7900, however, has the broadest chain wrap capacity of any rear derailleur in the marketplace, and you can use it with any combination of Dura-Ace cranks and cassettes, including a 50/34 with an 11/28.

The Shimano Dura-Ace RD-7900 rear derailleur is compatible with both the Shimano Dura-Ace ST-7900 and ST-7800 STI Levers. It is also compatible with all ratios of Shimano Dura-Ace CS-7900 and CS-7800 cassettes, as well as Shimano Dura-Ace CN-7900 and CN-7801 chains.

Tech Specs

Maximum Front Difference:
16 T
33 T
Compatible Components:
Claimed Weight:
166 g
Recommended Use:
road biking

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Unanswered Question

I have dura ace 7900 on my cyclocross /...

I have dura ace 7900 on my cyclocross / gravel bike and was hoping to put a bigger cassette on the back. It is my understanding that this derailleur has a 33T capacity, which means in theory i could run 46/36 chainrings in front w/ an 11-34 Shimano XT 10 speed cassette in the rear.

Chain Wrap = (Big ring - Small ring) + (Big cog - Small cog) = ( 46 - 36 ) + ( 34 - 11 ) = 33T

This should be the same as a compact crank w/ 11-28 casette ( 50 - 34 ) + ( 28 - 11 ) = 33T

Does anyone see a reason i can't do this?

Are there any issues swapping this in place...

Are there any issues swapping this in place of an existing Shimano 105 RD using TT shift levers? Planning on upgrading both derailleur sand the chain. Bike is already ultegra/105.

Hey Nick, that will work for you with no problems. The rate of cable pull hasn't changed between these componenets. If you have any other question feel free to give us a call at 888 276 7130

Other than weight, is there much of a...

Other than weight, is there much of a difference between the Dura Ace and Ultegra real deraileur?

how put back guer control cable

Avg. ride time: 4h 5m per week
  • Average ride time is based on Strava activity over the last 3 months. Give your reviews credibility by connecting your account.

quick change

    The most I like by this derailleurs is you feel the power when you shifting up and down, and is really easy to change the wheel

    Iwould like to get a Dura Ace 7900 R & F...

    Iwould like to get a Dura Ace 7900 R & F Deraileur 7900 chain 7900 cassette and use it with FSA-SL-K Light Crank does this make sense or should I just go with the 7800 Series of the same parts with this crank whats my best bet.

    That Makes Sense just a few things to watch out for. What Shifter are you planning, you need to match you Frt Der to your Shfter 7900 to 7900 or 7800 to 7800, Rer Der and Cass Don't matter but you need to use a 7800 or 7901 Chain with that FSA Crank.

    is the Dura Ace 7900 compatible with 105...

    is the Dura Ace 7900 compatible with 105 shifters?

    Yes, these will work with any Shimano road shifter. They all have the same cable pull ratios.

    I have a 2009 cannondale six5 with shimano...

    I have a 2009 cannondale six5 with shimano 105.the bike has never been doped or mishandled.the bike has been indoors of course since the day i got question is what can i upgrade to with this bike.better than the 105 system that came stock with there a better shimano system that will work better than what came stock with the 2009 cannondale six5.?its a ten speed cok and of course you know that.and if not whats the best price i can get for new left hand flight deck 10speed shimano shifter the one that came stock with my 2009 cannondale six5.?

    I have a 2009 cannondale six5 with shimano...

    Dura Ace or Ultegra will be an upgrade from what you are currently riding. Your Broken Left Shifter is a warrantee, you just need to take into any Bike Shop and they should be able to turn it around quickly.

    Write your question here...Did they ever...

    Write your question here...Did they ever make the rd 7900 GS derailleur? It is listed on the Shimano site.

    While Shimano did make a GS version of the 7900 rear derailleur it was not widely distributed. As demand for triple fronts wanes there will be far less availability for such a long caged derailleur on the market. There may be a chance you could locate one but I have checked with a few vendors and no one seems to stock them.

    Can this be used with a 50/34 and 11-34...

    Can this be used with a 50/34 and 11-34 rear cassette for touring? Thanks!

    No it can not. You will need what they call a long cage derailer, typically found in mountain bikes. This is a short cage derailer, you could run a 50/34 & 11-27, thats as good as is gets.

    can you use this type of derailleur on a...

    can you use this type of derailleur on a bike with down tube or bar mounted shifters.

    Yes, as long as you have a 10 speed indexed down tube shifter, or you can run ANY rear down tube shifter you have in the friction setting. 9 speed shifters may work too.