# Will Dura Ace 7800 rear derailleur work with an 11-28 cassette?



## Eric S

Will a Dura Ace 7800 rear derailleur work with an 11-28 cassette or is the 17 tooth spread to much? I have seen some specs that said the max spread was 16 but was wondering if anyone has some real world experience.
Thanks


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## Eric S

Sorry, it looks like this has been covered before and the 11-28 should work fine. I will be running 53-39 in front. Correct me if I am wrong here. Thanks


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## ukbloke

You definitely have enough capacity (tooth spread) since you are using a double up front. The only question is the clearance in the 28T cog with respect to the upper pulley in the RD. You will need the maximim amount of clearance that you can get from the B-screw. This typically requires insertion of the B screw in the opposite direction or maybe a longer screw. A 27T definitely works, and a 28T should work but it is getting very close to the absolute max. When installed check on the workstand that it runs smoothly without interference between the 28T and the upper pulley.

I'm thinking about 11-28 because they don't do a 12-27 at Ultegra level any more.


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## Baurice

Hi there
I'm running a 12-30 Ultegra cassette on DA 7800 derailleur with no issues. All I needed was a longer b screw (m4 15mm from local DIY) and to adjust it accordingly. 
Enjoy!


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## satanas

I've run 12-28 with 7800 RD with no problem, and in the past have used 30T or 32T cassettes with Shimano DA & Ultegra 8 speed road RDs. My experience is that 30T will normally work with zero issues, but that 32T is really pushing things to the limit - it may or may not work, depending on the chainstay length, derailleur hanger, phase of the moon, etc, but is best avoided.

IME, *every* Shimano short cage road derailleur back to the 1970s Crane will handle a 28T cog fine, provided chain length and adjustment is correct and you don't have anything weird happening like an immense difference between the chainwheels. YMMV.


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## SNS1938

I have a 11-28 on my 7800 with 39/53 that I use with no issues.


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