Shimano rear derailleur cages?!

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Jcgill
Posts: 50
Joined: Sat Apr 25, 2015 11:03 pm

by Jcgill

Hello,
I Would like to order a mix of ultegra 6800 and dura ace 9000 for a new build up i am planning.

What is the proper way to choose if you need a short cage or long cage rear derailleur? Is it the same for both 6800 and 9000 rear derailleurs?

I am probably going to go with an 11-28 rear cassette. Was thinking a short cage will work, just would like to verify prior to purchasing.


Thank you,
Jon

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BikeAnon
Posts: 399
Joined: Sun Mar 02, 2014 6:36 pm
Location: NY USA

by BikeAnon

Your mix choice will be fine. Short cage will easily handle 28. On some frames even 32.

If you'll ever want 32, get a GS derailleur. Otherwise, stick to an SS.

Nefarious86
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Joined: Sun May 25, 2014 4:57 am

by Nefarious86

Short cage for 28. Will take a 32 with careful setup if you don't cross chain for the odd occasion you may want it.
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eric
Posts: 2196
Joined: Tue Nov 11, 2003 9:47 pm
Location: Santa Cruz, California, USA
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by eric

The cage length determines the amount of chain wrap the derailleur can take up. That is separate from the largest cog the derailleur can handle.

Shimano publishes specs for both wrap and max cog for all their deraillueurs: http://si.shimano.com

Generally they are conservative on both the max cog and wrap. You can usually go a couple teeth more on both of those- i.e. a derailleur spec'd for a 28t max cog can almost always handle a 30t. It depends on the frame's derailleur hanger.

Current Shimano road derailleurs are speced for 28t or 30t max cogs.

eaglejackson
Posts: 259
Joined: Wed Aug 27, 2014 5:26 am
Location: PNW

by eaglejackson

Short cage should work with the 28. But... My wife recently bought a Specialized Roubaix in a 49cm. It comes with Ultegra 6800 Di2, 50-34 chainrings, and 11-28 rear cassette. The front derailleur would not shift cleanly from small to big ring, and the only solution we could come up with was to put the GS rear derailleur on. With the short chainstays, there was just too much chain in too short of a space to be taken up. Problem now solved and it shifts great.
Last edited by eaglejackson on Thu Apr 28, 2016 1:20 pm, edited 1 time in total.

eric
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Joined: Tue Nov 11, 2003 9:47 pm
Location: Santa Cruz, California, USA
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by eric

I've been able to run 30t cogs and 50/34 chainrings for extreme climbing races with Shimano 7800, 7900 and Sram Red short cage derailleurs.
This is on Cervelo R3 and R3SL frames, which have short chain stays. Because of the chain stays the smallest two cogs can't be used with the small ring because the chain rubs on the inside of the large ring.

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