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7900 crank with 7800 Dura Ace gruppo?

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7900 crank with 7800 Dura Ace gruppo?

Old 01-12-11, 12:57 AM
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BayAreaUser
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7900 crank with 7800 Dura Ace gruppo?

Hello guys,

I got a 7800 dura ace groupo (levers, derailers, chain, cassette) laying ready to be installed and wondered if i could use these items with a new 7900 crank.
I plan on using a 7800 chain, but would a 7800 cassette and 7900 crank work with a 7900 chain?
I searched and did not find and answer.

I figured since a substantial weight difference of the 7800 and 7900 gruppos is on the crank, i figure i would just chance that for now.
I plan on eventually making the transition to 7900 components as i find deals out there and complete the set up.

Thank you very much

Last edited by BayAreaUser; 01-12-11 at 01:18 AM.
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Old 01-12-11, 12:58 AM
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keisatsu
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You'll be fine.
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Old 01-12-11, 01:16 AM
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Chainring spacing's a little different, so you may need to be fairly precise on your FD cable adjustment. That'll come out in the wash once you get the 7900 FD and shifters.
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Old 01-12-11, 01:21 AM
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But, will i be able to use them for now without problems even though the chainring is different?
It may be a long while before I can actually fully upgrade components.
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Old 01-12-11, 02:07 AM
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keisatsu
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Originally Posted by mechBgon View Post
Chainring spacing's a little different.
Really, I had no idea. I've upgraded several 7800 BB/Cranksets to 7900 and can't recall any issues w/ the FD adjustment.
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Old 01-12-11, 02:39 AM
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Check out the Shimano chart:



Shimano says the 7900 crank should be used with the 7900 chain and 7900 front derailleur, but can be used with a 7800 cassette. I run this exact configuration on one of my bikes without a problem (actually full 7900 with 7800 cassette). This is what Shimano recommends, BUT I'm sure you can get away with the 7900 crank with the rest of the grouppo being 7800.
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Old 01-12-11, 06:26 AM
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Trucker Dan
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I ran a 7900 crank with everything else 7800 for over a year. No problems and shifted great. You can't use a 7900 front derailer with 7800 shifters. The cable pull is different.
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Old 01-12-11, 07:33 AM
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I use 2009 Campy 10 speed shifters with a 1985 "5 speed" crankset and a 1980 front derailleur ..... works fine ..... I would hope that Shimano 10 is cross compatible.
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Old 01-12-11, 07:55 AM
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I have a 7800 bike and upgraded the front crank, chain and rear cassette to 7900 with good results. The 7800 shifters work fine and this upgrade conforms to Shimano recommendations.
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Old 01-12-11, 10:25 AM
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Excellent! Thanks a lot! =)
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Old 01-12-11, 10:42 AM
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Shimano considers it a B-level setup, but it works well enough to go on with.
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Old 01-12-11, 12:01 PM
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no it won't work... ;-) BUT I have a 7800 crankset I'll gladly trade you for your 7900 crankset.
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Old 01-12-11, 01:08 PM
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Originally Posted by Trucker Dan View Post
I ran a 7900 crank with everything else 7800 for over a year. No problems and shifted great. You can't use a 7900 front derailer with 7800 shifters. The cable pull is different.
Or 7900 brakes with 7800 shifters either.
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Old 01-12-11, 02:47 PM
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I'm running a 6700 crank with 7800 group and 6700 chain. It's working great.
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Old 01-12-11, 06:43 PM
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Thanks guys.
Right now I'm looking for a 7900 crank. I can't find anything under 400, but see plenty of 7800 new units going for 200.
Hope the cost is worth it!.
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Old 01-12-11, 06:48 PM
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Screw the weight.... the 7800 looks so much better !
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Old 01-12-11, 07:15 PM
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Originally Posted by MegaTom View Post
Screw the weight.... the 7800 looks so much better !
incorrect.

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Old 01-12-11, 07:47 PM
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Originally Posted by BayAreaUser View Post
Thanks guys.
Right now I'm looking for a 7900 crank. I can't find anything under 400, but see plenty of 7800 new units going for 200.
Hope the cost is worth it!.
If it has to be a 7900, here is a set for $339.

https://www.bikewagon.com/Shimano-Dur...-p8947551.html

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Old 01-12-11, 07:49 PM
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i just got offered a brand new, still in box 7800 crank for $220. I may jump on it.
What's the total weight difference of the two units? I read somewhere a bit over 1/4 lbs.
Wonder how much of that is the crank alone. I don't foresee a lot of weight saved on the other pieces.

edited. I just looked it up. 15 gram difference. Although the 330 price is tempting. 15 grams are not worth $120+ to me =(
Not right now, or am i missing something?

Last edited by BayAreaUser; 01-12-11 at 07:55 PM.
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Old 01-12-11, 08:08 PM
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Originally Posted by BayAreaUser View Post
am i missing something?
Not, not much, except that 7900 front shifting is even slicker than 7800, if such a thing were possible. Due to the chainrings alone? Probably the redesigned shift levers and FD cage make a contribution.
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Old 01-12-11, 08:11 PM
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the rings are stiffer on the 7900
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Old 01-08-20, 04:32 PM
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Front Derailleur compatibility

Originally Posted by Trucker Dan View Post
I ran a 7900 crank with everything else 7800 for over a year. No problems and shifted great. You can't use a 7900 front derailer with 7800 shifters. The cable pull is different.


Front derailleur compatibility-

Can I
use a Shimano FD-7900 front derailleur with a Shimano FC-7800 Crank Set?
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Old 01-08-20, 06:33 PM
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Originally Posted by Jharrington View Post
Front derailleur compatibility-

Can I
use a Shimano FD-7900 front derailleur with a Shimano FC-7800 Crank Set?
Yes Also the post you quoted by trucker dan is incorrect.

Last edited by shelbyfv; 01-08-20 at 06:36 PM.
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Old 01-08-20, 06:37 PM
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Originally Posted by shelbyfv View Post
Yes Also the post you quoted by trucker dan is incorrect.
Thanks!
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Old 01-08-20, 06:38 PM
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Thanks! I’m having trouble adjusting the front derailleur.
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