# 6700 Crank verus 7900



## JSWhaler (Nov 25, 2009)

I'm currently looking for a new compact crankset. I'm debating over the 6750 or the 7950. Will I notice any performance difference between the two? Or should I save my money and stick with the Ultegra? The rest of my setup is DA 7800.


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## BikeFixer (May 19, 2009)

the 6750 is compatible with the 7800 front derailleur the 7950 is not


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## JSWhaler (Nov 25, 2009)

Oopps. I just ordered a 7950 crankset. What FD will I need to make this work then? I didn't think the crankset mattered.


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## BikeFixer (May 19, 2009)

It will probably work better with the existing frt der you have than trying to use the 7900 which is designed to ONLY work with the 7900 sti levers. Give it a try and see if it works if not you might have to trade in the 7950 for a 6750


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## JSWhaler (Nov 25, 2009)

From what I could find the 7950 crankset should work with DA 7800 components. When it comes in I'll give it a try. I plan on sticking with a 7801 chain or maybe I'll splurge for a KMC.


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## BikeFixer (May 19, 2009)

it's really slightly off on the spacing but it is a good "b" compatibliity so you should be ok.
Use the 7900 chain it's awesome


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## LGD (Aug 14, 2009)

BikeFixer said:


> the 6750 is compatible with the 7800 front derailleur the 7950 is not


 These two cranksets are equally compatible with your front derailleur. The only front derailleur issue with any of the new Shimano components is the 7900 front derailleur is designed to work only with the 7900 STI levers, and vise-versa. Many have fudged it to work either way, but it is not ideal. There are no issues relating to the crankset/chainrings vs. the derailleur.


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## JSWhaler (Nov 25, 2009)

I'll give the 7900 chain a try. I'll also pick up some KMC quick links.


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## fxtri (Mar 17, 2006)

JSWhaler said:


> I'll also pick up some KMC quick links.


Don't bother, 7900 chain comes with a quick link.

Edit: Just found the other thread about 7900 link failure, so KMC links may be better, though I have not had any problems with the 7900 link.


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## BikeFixer (May 19, 2009)

Don't use the quick link. The Shimano one is discontinued due to some stretching issues and they are working on a new one. The KMC isn't really compatible, I know somebody will say it is but trust me it's not that great.
Just use a pin and be done with it. You can clean your chain on the bike and by the time you really need to take it off to clean it, it's going to be time to replace it anyway


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## DaveT (Feb 12, 2004)

BikeFixer said:


> Don't use the quick link. The Shimano one is discontinued due to some stretching issues and they are working on a new one. The KMC isn't really compatible, I know somebody will say it is but trust me it's not that great.
> Just use a pin and be done with it. You can clean your chain on the bike and by the time you really need to take it off to clean it, it's going to be time to replace it anyway


KMC not compatible? News to me. I've been using one on my 10-speed Shimano rig for several years and now have it on my 6700 equipped bike for almost 1,000 miles and no issues. Do you have any knowledge of factual events that would lead you to think that the KMC Missing Links aren't working properly?


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## jmoleary (Apr 29, 2008)

*7950 crank with*



JSWhaler said:


> Oopps. I just ordered a 7950 crankset. What FD will I need to make this work then? I didn't think the crankset mattered.



Have you tried the 7950 crank with the 7800 FD yet? Has anyone? I understand it SHOULD work but I would like to hear from anyone who can confirm that it DOES work -- and how well.

I've got a bike with 7800 all over it except for an Ultegra compact crank. I only went with Ultegra because DA didn't offer a compact at the time. Now DA offers a compact, I'd like to switch (I'm also going to shorter crank length arms so that's not the only reason) but not if I have to also switch front derailleurs or shifters.


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## jmoleary (Apr 29, 2008)

LGD said:


> These two cranksets are equally compatible with your front derailleur. The only front derailleur issue with any of the new Shimano components is the 7900 front derailleur is designed to work only with the 7900 STI levers, and vise-versa. Many have fudged it to work either way, but it is not ideal. There are no issues relating to the crankset/chainrings vs. the derailleur.


Can you tell me how you know this? Is it from experience? I'm not doubting you in the slightest but I need to be certain before I pull the trigger and actually buy a 7950. That's a lot of coin to be taking a chance on.


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## JSWhaler (Nov 25, 2009)

If I get the time today I'll be putting on a 7950 crankset and DA 7900 chain. Rear cassette Sram Red, everything else DA 7800.


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## jmoleary (Apr 29, 2008)

JSWhaler said:


> If I get the time today I'll be putting on a 7950 crankset and DA 7900 chain. Rear cassette Sram Red, everything else DA 7800.



Once you get a ride or two in, I would love to hear your first impressions


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## LGD (Aug 14, 2009)

jmoleary said:


> Can you tell me how you know this? Is it from experience? I'm not doubting you in the slightest but I need to be certain before I pull the trigger and actually buy a 7950. That's a lot of coin to be taking a chance on.



Yes, experience and the fact that nothing changed in the crank which would have an effect on the front derailleur. Heck, I've set up an older Ultegra front derailleur with the new 7900 crank and it works just fine. I've also set up the new 7900 front derailleur with cranks other than 7900 and it works great.

Repeat: The only issue with front shifting, having to do with 7900 series components, is front derailleur/shift lever compatibility. Otherwise, 10-speed Shimano is 10-speed Shimano. The newer pieces tend to shift a bit cleaner and run a bit quieter, but that is it- as far as compatibility goes.


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## pgk (Jun 30, 2008)

+1 on the KMC, Iv'e been running their chain and quick link on my 7900 group with zero issues.


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## JSWhaler (Nov 25, 2009)

Well I'm currently running the 7950 crankset the 7900 chain. I took out the quick links but haven't put in the KMC link. The rest of my components are DA 7800 and I'm having no shifting issues whatsoever. I must say the shifting seems a bit smoother than my FSA. The crank is also a nice upgrade in stiffness. I can tell when I stand up on the cranks. Overall I'm very happy. I've also been playing around with some sram red cassettes and they to shift nice and smoothly, just a tad noisier than DA's. I think I'll be upgrading my rear d and shifters to Red. 

Final note the crank looks much better in person than in pictures.


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