Question Ultegra 6600 Flight Deck

[The_Paulino]

I have Shimano Ultegra 6600 rear derailleur with a 10 speed 12-25t cassette which I am looking to change for a 10 speed, 11-34t or 11-36t. Can someone tell me if this will work without changing the derailleur?

 

[King Boonen]

It's highly unlikely. I've seen a bike running 53/39 and 11/32 working but it's very dependent on the mech hanger and the chain wrap on the smaller sprockets was terrible.

 

[Invicituz]

No, it will not work. See specifications for Shimano Ultegra RD-6600 GS and SS type, at this link:

https://si.shimano.com/pdfs/si/SI-5VG0C-001-ENG.pdf

 

[The_Paulino]

Thank you. I read through it and I have a short cage derailleur so 29t would be the Max.

So maybe I’ll upgrade both the cassette and derailleur -would the RD-R8000 rear derailleur work With the 6600 10 spd shifters??

or any other suggestions?

 

[King Boonen]

No, the pull ratio on the 11 speed derailleurs is different so it won't work, even if you ignore the extra gear. You can probably pick up a GS cage 10 speed 105 or Ultegra derailleur on ebay pretty cheaply.

Other options are:

11 speed shifter, cassette and derailleur (you don't need to change the crankset, front derailleur or shifter, they'll be fine).
Smaller chainrings (6600 is 5-bolt though so this will likely mean a new chainset).