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Another Dura Ace Compatability Question....Sorry

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Another Dura Ace Compatability Question....Sorry

Old 07-19-13, 08:11 AM
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mcoomer
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Another Dura Ace Compatability Question....Sorry

I need to replace my brifters and rather than put another set of 7800's on the bars I'd like to upgrade to 7900's. I've found a couple different versions of Shimano's compatibility chart and I'm a bit confused about whether my current crank will suit my needs. Currently, S-Works Tarmac SL2 is all DA 7800. My plan is to replace both brifters and the derailleurs. I'd like to keep my crank, cassette, chain, and brakes. Looking at the different charts I've found on the web it appears the crank, cassette, and chain combo will work but a couple of these charts say that shifting could be slower with the 7800 crank. The chart on the Shimano site doesn't show the 7800 crank as compatible.

Anybody running 7900 brifters and derailleurs with 7800 crank, cassette, chain, and brakes? Will this work well?

Thanks,
Mike
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Old 07-19-13, 03:22 PM
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WE have not done the DA level pairing you ask about but have done a few 105 and Ultegra ones and have had no problems. We are aware of the brake lever leverage differences and have discussed this with our customers. The newer brake levers produce a bit less leverage and make the braking feel a bit more firm/stiffer when the pads contact the rim but need a bit more strength to haul things down. these differences have not been even committed on by our customers after the swap out. So, for them, the leverage differences are not an issue. Again WRT shifting, no problems. Andy.
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Old 07-19-13, 07:44 PM
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The cranks are functionally the same for shifting, there will be no issue there.

BTW you don't have to replace your derailers unless you want to. They will work exactly the same. The stuff you're looking at is all 10 speed Shimano so there won't be any issues.

IMO the 7900 STI shifters are a significant improvement over the 7800, particularly due to the under the bar tape cable routing.
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Old 07-19-13, 10:19 PM
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Originally Posted by FastJake View Post
The cranks are functionally the same for shifting, there will be no issue there.

BTW you don't have to replace your derailers unless you want to. They will work exactly the same. The stuff you're looking at is all 10 speed Shimano so there won't be any issues.

IMO the 7900 STI shifters are a significant improvement over the 7800, particularly due to the under the bar tape cable routing.
To be clear, I can keep the 7800 front and rear derailleurs and they'll work with the 7900 brifters? I haven't dug a lot on this but what I have seen indicates they won't work. I'd love to be able to save some cash by replacing only the brifters. Probably make my wife happy too when she sees the credit card statement.

Mike
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Old 07-19-13, 10:32 PM
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Shimano make $ by systemizing their products. And they do a very good job this way. But to my knowledge the incompatibility of 7900 and 7800 levers is the brakes and not the gears. Our experience at work has shown this. That the same ders can work with "off series" STI levers (having traditional leverages and exposed cable routing) as well as new inclosed casing routing STI levers also reinforces this. But much of what you read is simple rehashing of the company line. And Shimano has always said only "one way" works. They have gone to the bank with heavy pockets with this marketing approach for years. IIRC the only Shimano ders that won't work with their road STI levers are the 10 speed generation of ATB offerings. They have a different cable actuation ratio. Andy.
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Old 07-19-13, 10:35 PM
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Originally Posted by mcoomer View Post
To be clear, I can keep the 7800 front and rear derailleurs and they'll work with the 7900 brifters? I haven't dug a lot on this but what I have seen indicates they won't work. I'd love to be able to save some cash by replacing only the brifters. Probably make my wife happy too when she sees the credit card statement.

Mike
Your rear dérailleur will work perfectly with a 7900 shifter, however a 7900 front dérailleur will have to be used as it (and the shifter) have different pull ratios. All the rest of your current running gear will work fine too.

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Old 07-20-13, 12:19 AM
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Originally Posted by mcoomer View Post
To be clear, I can keep the 7800 front and rear derailleurs and they'll work with the 7900 brifters? I haven't dug a lot on this but what I have seen indicates they won't work. I'd love to be able to save some cash by replacing only the brifters. Probably make my wife happy too when she sees the credit card statement.
To be more clear, the 7800-7900 brifter swap does not require ANY other changes. Shimano didn't change the cable pull of the derailers so you're good there. The brakes may feel a bit different but I'm not even sure you'll notice. Just put on some nice soft Kool Stop salmon pads and the brakes will be even better than stock.
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Old 07-20-13, 06:28 AM
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Originally Posted by FastJake View Post
To be more clear, the 7800-7900 brifter swap does not require ANY other changes. Shimano didn't change the cable pull of the derailers so you're good there. The brakes may feel a bit different but I'm not even sure you'll notice. Just put on some nice soft Kool Stop salmon pads and the brakes will be even better than stock.
The 7900 front shifter and derailleur must be used together as Shimano did change the ratios to get quicker, more positive front shifting. If a non-7900 front der is used, it will undershift and not work well at all. In the Shimano line, virtually the entire 10-speed road rear ders wiill work with virtually all 10-speed road shifters and the same is true for the front ders, with the exception of the front 7900.
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Old 07-22-13, 10:15 PM
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Well, I'm going to pick up a set of brifters and give it a whirl. I've heard that the front derailleur has to be changed too, but as shown in this thread for every person that says yes there's another that says no. Anyway, front derailleurs are cheap so if I need one, I'll get one. I'm simply pleased to hear that crank, cassette and chain are OK as the new cranks are crazy expensive.

Thank you for the replies.

Mike
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Old 07-23-13, 06:47 AM
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Mike, It's always best to test the new parts with existing parts, then buy extra if needed. More often than not through the history of D-A there has been some compatibility issue with the other road groups or between different series of D-A. Many have a work-around discovered by clever mechanics.

Brad
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