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I haven't been able to find anyone in the forum with my exact set up, so here it goes...

I have a Trek 5500 from 2003. It was originally a DA 9 speed. Last year I replaced it with 10 speed DA STI, 10 speed cassette and chain. FD, RD and the crankset have remained the same at 9 speed.

The rear shifts just fine but I am having a hard time with the front. Despite my best efforts the chain often falls off when going from big ring to small. Also, 53x23 and 53x21 is almost unusable due to excessive rub.

My question is, can I just replace the FD or do I need to replace both FD and the crank? If I need to replace the crank do I have to replace the BB as well (I plan on staying with Shimano)

thanks!
 

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Sounds like the limit screw on your FD needs adjustment. Your chain shouldn't be dropping off no matter what FD you're using. You might not be able to get rid of some slight rubbing in a 53x23 because of the angle that forces the chain in, (shift to the smaller ring and down a cog or so for the same ratio and less strain on the drivetrain).

If you upgrade, (which I don't think you HAVE to) you will need a new BB for a 10s DA crank. It is outboard now, a completely different system from the 7700 series. Good luck! :)
 

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This sounds like a setup issue more than a compatibilty issue.

The main difference between a 9 and 10 speed FD is the width of the cage. The wider 9 speed cage should reduce rubbing, not make more of it. The difference in cranks is small but significant: the spacing between the two rings is reduced in the 10 speed crankset. Buying new cranks will mean faster shifting because the chain has less distance to travel.

I would check the height and angle of the front derailleur. Also, most 9 speed DA shifters have a trim click, make sure that you are using this feature correctly.

But to answer your question: you can replace either the front deralleur or the crankset, or both. Or none :)

Hope that helps

Tristan
 
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