# 7900 Rear Deraileur with 7800 shifters?



## ReedJay (Feb 5, 2007)

The 7900 rear deraileur indicates that it will work on a 28T gear. I'd like to install the 7900....if it will work with my 7800 shift levers? I realize that Shimano does not recommend it...but I've heard that it works. Does anyone know? Thanks


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## dover (Apr 5, 2007)

yep, works fine. no compatibility issues


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## ksanbon (Jul 19, 2008)

Reed Jay - Do you have a 7800 rear derailuer? My Tarmac came with 7800 and SRAM 11-28 and it works fine.


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## ReedJay (Feb 5, 2007)

Yes, I have 7800 rear deraileur on my Madone 6.5. Installed the Sram 11-28 and the upper pulley wheel rubs on the 28 tooth gear. Mechanic told me that the 7800 is only rated to work with a 27 tooth.


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## Corndog (Jan 18, 2006)

Did you turn out the B adjustment? I've gotten 7800 short cage ders to work with 28T cogs, no problem. Heck, I've even gotten a 30T to work.


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## ReedJay (Feb 5, 2007)

Yes, B screw is all the way in and the pulley still hits on the 28t. Thanks


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## Hardtail (Feb 4, 2003)

7800 won't work properly with a 28
7900 rear der will work fine with a 7800 shifter


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## ReedJay (Feb 5, 2007)

Yep. Replafed the 7800 rear der. with a 7900 and the 11-28 sram red cassette..kept the 7800 shifters .works fine!


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## Corndog (Jan 18, 2006)

Hardtail said:


> 7800 won't work properly with a 28


Yes it will...... give it a try! I've setup a 30T rear cog on a 7800 der with no problems. Shimano is VERY conservative with it's cog recommendations.


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## fast ferd (Jan 30, 2009)

I sure like my 27 or 28 cog for the steepest pitches. It's only a matter of time before I go to a 30t. Or - horror of horrors! - a triple crank!


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