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In my previous question we determined that I probably need new chainrings. I was/am planning on replacing the chainrings, and leaving the original crank.

Now this bike is running Shimano 105 FC-5600 kit. I refer to the Shimano drive-train compatibility chart here which says that that the FD-5600 front derailleur needs FC-5600,FC-5650,FC-R600 or FC-R550 front cranks.

Since I have to replace it, I wouldn't mind upgrading to a Ultegra-level chain-ring. According to (my reading of the chart), this is not possible. (which seems strange, I would have thought any 130BCD chainring with the same screw type should work. Is there a problem with derailleur clearance or something?)

1) Is this correct?

2) If so, is there a compatibility chart with other brands? (FSA/SRAM - obviously Campy wouldn't work!)

Thanks in advance

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1 Answer 1

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The current Ultegra chain rings are in fact physically compatible with the 105. They do not look good on the 105 crank, however, because when Shimano redesigned the Ultegra and DuraAce level cranks to their Hollowtech II design, the made the chain rings hollow as well.

Th point where the chain ring meets the crank arm is noticeably thicker, and shaped quite different on the Ultegra chain ring and crank, compared to the 105.

This is the 105 FC-5700, which is newer than your FC-5600.

105 crank

This is the Ultegra FC-6700, which compares to the FC-5700.

Ultegra crank

See the extra shape and thickness where the chain ring bolts are? That is why they do not list Ultegra rings as compatible with 105.

You can physically bolt them up, and they will work, but they look bad, and you don't get most of the benefits of the Ultegra ring, (mainly added stiffness), without the whole crank.

A set of Ultegra rings will cost 150 dollars, and a whole crankset, including rings will be around 250 dollars, so it might be worth just doing th whole crank, if you're interested n upgrade.

Otherwise, just stick with the 105.

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Thank you again! I did think about just getting new 6700 cranks, but then (again the compatibility chart) I will need need shifters and front derailleur. So if I just found some FC-5700 chain rings, I should be OK? –  J.S. Aug 6 '11 at 3:38
    
The crank will, for certain, work with your 105 kit, assuming they are both set up for a 10 speed cogset. With those part numbers, it should be. –  zenbike Aug 6 '11 at 4:18
    
And yes, you can use FSA 130 BCD chain rings, but they will not shift as well as the Shimano with other Shimano parts, because of the difference in ramp and pin design. –  zenbike Aug 6 '11 at 5:02
    
Thanks zenbike. Indeed I am running 10 speed atm. Are you saying both 5700 and 6700 crankset are backwards compatible with my 5600 shifters/derailleurs, etc? (I only ask because that is not what the Shimano chart seems to suggest) –  J.S. Aug 6 '11 at 6:52
    
Yes, I am. Any Road 10 speed Shimano shifters will work with any 10 speed road Shimano drivetrain, except the Di2 electronic. The other thing to watch for is compact or standard crank sizes, but that is an adjustment issue, not a failure of compatibility. –  zenbike Aug 6 '11 at 7:28

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