# Replacement for Shimano FD-6503



## willfavata (Feb 24, 2010)

*Replacement for Shimano FD-5603*

Time to replace my Ultegra 5603 FD (9 speed triple, clamp-on) with??? They are kinda scarce on eBay, so I need to know if any of the more recent FD's will work. Thoughts?


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## zriggle (Apr 16, 2008)

Any **03 derailleur should work, IIRC. Might be something iffy with the FD-7803, but I'm not sure.

For certain, the 5503, 5603, 6503, 6603, 6703 all work. You could probably even go older -- Shimano FDs are compatible between 9 and 10 speed, with the exception of the new fancy Dura-Ace.


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## willfavata (Feb 24, 2010)

Thanks. Good to know that there are a number of good options.


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## Metaluna (Aug 26, 2005)

I can't speak for compatibility across 9 and 10 speeds, but there are definitely compatibility issues within the 10 speed range. For example, the Ultegra FD-6603 is highly tuned for Ultegra triple cranks, and does not work well at all with Tiagra or 105 triples which have a 50T large chainring vs 52T for the Ultegra 6603.

I'm not sure if there's an issue in the other direction though (i.e. using a 105 derailleur with an Ultegra or other 52T chainring crankset), but I definitely had problems mixing an Ultegra 6603 FD and a Tiagra 50-39-30 crank.


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## willfavata (Feb 24, 2010)

I plan to continue using my Ultegra FC-6503, triple (52-42-30), 9 speed system,12-25 freewheel. In light of this, what are your thoughts on a FD upgrade path? Are you in general agreement with the first post that any of the newer triple FD's will work without complication? Thanks.


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## Metaluna (Aug 26, 2005)

My experience with Shimano triples is limited, so hopefully someone who has used them more extensively can comment. But, the 52-42 tooth difference of your crank concerns me. The FD-6603, 6703, 7803, etc are specified for a *minimum* 13T difference between the big and middle chainrings. The issue is that the inner cage on these FD's has a very deep drop to it. When paired with a crank that only has about a 10T difference between the big and middle chainring, and thus a relatively small difference in chainring diameters, that inner cage plate will rub on the middle chainring when you have the cage shifted to the big ring. You can try to correct this by raising the height of the FD so that the inner cage clears the middle ring, but then the outer cage plate will be too high and the chain will be vulnerable to falling off when shifting to the big ring, and shifting and trimming will be sub-optimal.

In your case you might want to stick with the 105 (5603) or Tiagra (4503) derailleurs, which are designed to work with 50-39-30 triples (11T difference, but probably close enough). These are spec'ed for a max 50T big ring, but that might not be as big of an issue as the inner cage plate. Or, you could look into swapping your middle chainring to a 39T, if that's possible.


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## sdstp (Aug 25, 2011)

Willfavata, what did you end up getting? I have the same issue and can't find a FD-6503.


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## padudle (Oct 11, 2009)

I am having trouble fitting an FD-6603 to an Ultegra 9-speed triple crank for exactly the reasons given by Metaluna. I think you would be better off with a mountain bike front derailleur or stick with an FD-6503 that you know will work.


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## 251 (Nov 2, 2009)

FWIW, I had issues using a 6600 (10-speed/double) FD with a 9-speed chain. The narrow cage on the FD didn't allow enough room for the slightly wider 9-speed chain and required frequent trimming to keep it quiet. It would only accomodate a 3-4 cog range on the cassette before it would rub.

I got fed up with the noise and constant trimming, so I ended up upgrading the rest of the drivetrain to 10-speed. I already had the 6600 RD, FD, crank, callipers, so all I needed was the chain, cassette and levers.


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