LKA 

Hello All,

Sorry to present such a mundane question, but I could not find an answer from Google, the Shimano tech doc site, or a search here.

I am looking at possibly purchasing the Ultegra FC-6600A crankset for my H-a-o-l-e, and I found that two types were made: an FC-6600 and an FC-6600A. Other than different part #s, I can find no other information whatsoever that even hints at what the difference[s] might be. Given the depth of the search I made, I realize that it's quite possible that no one knows the answer, but I thought I'd give it a try here anyway.

Here is a link to the Shimano tech doc:
EV-FC-6600-2365E.pdf

Thanks in advance for your time.

HillRider

I checked Shimano's dealer manual and also found no explanation. The only differing part numbers seem to be the left side crank arms and all lengths (165 to 175 mm) have two different parts, one for the FC-6600 and one for the FC-6600A, but no way to tell what the differences are from the picture. All the other parts are identical.

You might call Shimano USA and see if anyone there knows.

CliffordK

I wouldn't worry about the differences. There was likely a small design revision that Shimano incorporated, so I'd guess the 6600a is newer.

In general xx03 models are "triples".

I'm also seeing a 6604 crankset that looks like it may be painted in darker colors, and may be a newer release.

CliffordK

Oh, one thought.

When did Shimano release the SG-A chainrings? Could that be related?

LKA 

Haha, I was thinking the same thing. That whole A-type, B-type chainring nonsense still makes my head hurt. But I couldn't find even a hint as to whether that was the case. Learning the differences between MegaExo & Hollowtech II was already pushing me to the edge, LOL.

Thanks to all for your input. The part's aren't ridiculous expensive so I think I'll just go for it. And all this because I want to pre-empt a MegaExo/FSA SLK failure.

Davet

Maybe the 6600A was the Ice Grey colored crank?

desertdork

I just took a look in a box of parts and there's a NOS Ultegra crank which happens to be FC-6600A. The only reference the accompanying instructions makes regarding the "A" designation is to make sure you don't try to mismatch the arms; e.g., don't try to mix a 6600 right arm with a 6600A left arm. I don't know but suspect it probably has to do with the pattern of the splines or the orientation of the "key." The chainrings are "B-type" which I believe is Shimano's standard 53/39 double, whereas "A-type" rings mate with a 42 inner.

CliffordK

SG-A, SG-B, and SG-D isn't quite "nonsense".

The idea was to match small and big rings for better shifting.

I think the problem is that Shimano never expanded it enough to really offer a full range of sprockets.

And, now, everything has shifted as they've added more gears on the rear, although I'm still not convinced front sprockets needed to be changed that much.

And, of course, they've failed to continue to support the products, so about the time a chainring might wear out, Shimano discontinued selling spares.

I like the possible color distinction above as a difference between 6600, 6600a, and 6604. I'm not sure I have any of those cranks... I like the 6500 series

Davet

IIRC Shimano made a change in the 5600/6600/7800 left side crank arm mounting to include the ‘key’ on the NDS crank arm mount to prevent that arm from loosening and coming off if not properly tightened. Perhaps that’s the A model designation.

desertdork

Ultegra SL was the "ice grey" version. FC-6601-G was the double, and FC-6604-G was the triple.

LKA 

As a newb poster, I must remind myself that how one words their thoughts here [@bikeforums.net] is under as much scrutiny as the topic. I apologize for making light of a not-so-insignificant technical issue as chainring compatibility, because indeed, you are spot-on.

When I wrote that comment, I was thinking about components in general...that there's just too many darned bike parts to keep straight in the head. I was content just thinking about square-taper BBs for the past 29 yrs; and now that I've gotten back into cycling, parts [all parts, not just BBs] & their variants have proliferated beyond any concept of variety I could ever have imagined.

FWIW: I am so over bottom brackets. Now those with eidetic memory will LMK that bike part proliferation is merely my problem, LOL. <sigh>

G'day & thanks for the input. I'm beginning to like bikeforums.net.

CliffordK

I will agree that the proliferation of incompatible parts is an issue for the bike industry in general, and potentially one of the issues that is harming the LBS model.