# Ultegra 10-sd r. derailleur w/9sp shifters?



## jorgy (Oct 21, 2005)

Can I use a 6600-series rear derailleur with 9-speed STI shifters and a 9-speed cassette?


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## LC (Jan 28, 2004)

works fine.


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## Optimus (Jun 18, 2010)

Yes, you may!


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## SunnyinCO (Oct 26, 2010)

Have the same on my bike and even my LBS (who follow the manual like you would not believe) said it is fine. The R.D. is just a spring


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## jetdog9 (Jul 12, 2007)

SunnyinCO said:


> The R.D. is just a spring


The spring that some people look at first to see if your bike is "cool" or not...


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## slonoma98 (Jun 22, 2005)

Works fine. When I was upgrading I even ran a 10sp shifter with 9sp cassette for a while without issues


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