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Anyone convert a Dura-Ace 7800 crank into Compact gearing?

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Anyone convert a Dura-Ace 7800 crank into Compact gearing?

Old 07-17-10, 01:50 PM
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Anyone convert a Dura-Ace 7800 crank into Compact gearing?

I’m curious to hear anyone’s thoughts on converting a Dura-Ace 7800 crank into compact gearing (50/34). I see Shimano made a D/A, 7800 50T outer chain ring and 34t inner, Ultegra 6600 ring… I realize Shimano’s official position would speak against using both with their 7800 double, front derailleur – but I’m curious to hear opinions please.


I really like the 7800 crank I have now and I read Shimano’s claim that the new 7900 compact isn’t compatible with 7800 components (other than the Bottom Bracket).

I guess I could buy the D/A 50T and a 6600 Compact crank, switch the outer rings, wipe off the Ultegra lettering & sharpie Dura-Ace… but I doubt anyone will buy that.

Thank you,
Trent
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Old 07-17-10, 02:26 PM
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yes to an extent, I used a 50 t ring with a 39 and I liked it but I finally went with a compact 50/34.
My preference with shmano would be a 50/36 if they made compact ring of 36 because to me the 50/34 is too much of a drop.
I like the 50/34 though and it has helped cut down on my arthritis flare-ups in my knees due to more spinning, than hammering
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Old 07-17-10, 02:34 PM
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No, you can't go below 38t for the inner ring on a 130bcd standard double.
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Old 07-17-10, 05:56 PM
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Originally Posted by Trenton
I’m curious to hear anyone’s thoughts on converting a Dura-Ace 7800 crank into compact gearing (50/34). I see Shimano made a D/A, 7800 50T outer chain ring and 34t inner, Ultegra 6600 ring… I realize Shimano’s official position would speak against using both with their 7800 double, front derailleur – but I’m curious to hear opinions please.
As someone already posted, you can't fit a smaller ring than 38T on a standard double (and you'll have go non-Shimano anyway even to get 38T). The 50 ring will work fine though. In fact front shifting will be even better because of the smaller gap between 38/39 and 50 rather than 53. You should lower the FD a little to compensate for the smaller 50 ring, but once you do it will work flawlessly. I have run this combination with no problems whatsoever.

Originally Posted by Trenton
I really like the 7800 crank I have now and I read Shimano’s claim that the new 7900 compact isn’t compatible with 7800 components (other than the Bottom Bracket).
I am using a 7950 compact double and Dura-Ace 7900 chain with a Wipperman link and Ultegra 6600 cassette/RD/FD/shifters and and the setup works perfectly. The new DA 7900 chain is the same pitch and width as 7800 as far as I know, so you would expect it to. I guess what must be new is some subtle machining of the link profile to assist with shifting.

What may not be compatible between 7800 and 7900 is shifters and RD as the pull ratio is different from what I hear. But even that doesn't seem to matter with front shifting. My Ultegra 6600 FD shifts the DA7950 compact just fine. I didn't even have to adjust it when I took the Ultegra compact crank off and replaced it with the DA7950.

Originally Posted by HAMMER MAN
My preference with shmano would be a 50/36 if they made compact ring of 36 because to me the 50/34 is too much of a drop.
SRAM make a 36T ring and it is 100% compatible with Shimano compact cranks. 36/50 is a good flatland combo for solo riding and I am going to try the SRAM 36T ring from my old Ultegra compact on the new DA7950 crank when I get a chance.

Last edited by scirocco; 07-17-10 at 06:15 PM.
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