changing Shimano rd cage

[onsight512]

I've a 7900 rd and would like to put a medium cage on it from a 6700. Is it possible to buy just the cage from the Ultegra rd, or do I need to buy a complete rd for the part(s)?

I have a 50/34 up front and would like to run an 11-32 cassette.

[dave thompson]

I've a 7900 rd and would like to put a medium cage on it from a 6700. Is it possible to buy just the cage from the Ultegra rd, or do I need to buy a complete rd for the part(s)?

I have a 50/34 up front and would like to run an 11-32 cassette.
I'd suggest that you buy the 32t cassette first and try it with your current derailleur. I'd wager they will play nice together.

When Shimano came out with their 5700/6700/7900 series of components, they changed the geometry of the rear derailleurs. I can't rember exactly how I found out that my 6700 short-cage rear derailleur will work with an 11-32 cogset but it does, without issues. I've tried it on multiple bikes of mine, some custom built, others production, made in Taiwan, USA, France, steel, carbon and aluminum. In every single case that combination has worked for me. Usually, though not always, the B screw has to be screwed all the way in and the chain had to be sized for the big/big combination.

The cage length has nothing to do with the derailleur's ability to handle a larger tooth count cog. Cage length had to do with how much chain it will wrap and is necessary when using a triple chainring.

[oldpotatoe]

I've a 7900 rd and would like to put a medium cage on it from a 6700. Is it possible to buy just the cage from the Ultegra rd, or do I need to buy a complete rd for the part(s)?

I have a 50/34 up front and would like to run an 11-32 cassette.

To answer your question..if it has a part number, the 'part' is available somewhere. Probably the only place will be shimano,USA, via a LBS but maybe not even there. 'May' be cheaper/easier to just get a used 6700 longer cage rear der..to also make sure it fits(I think it does).

You can get the part number here.

http://si.shimano.com/

[Gummee]

To answer your question..if it has a part number, the 'part' is available somewhere. Probably the only place will be shimano,USA, via a LBS but maybe not even there. 'May' be cheaper/easier to just get a used 6700 longer cage rear der..to also make sure it fits(I think it does).

You can get the part number here.

http://si.shimano.com/

I've successfully transplanted XT long cages to Ultegra uppers and Ultegra cages to XT uppers.

Trick is to stay with the same 'family' (6600 and the corresponding XT generation)

IIRC D/A 7700 and XTR of the same vintage will work together too, but someone's going to have to check that.

I know 6800 small parts are available 'cause I've had to swap out a few crashed bits last year. 6800 seems to be susceptible to bending at the bolt that mounts the derailleur to the bike....

Also IIRC they changed the geometry on the longer cage 6800 derailleurs so that even if you do swap in a longer cage to a short cage 6800, it's not *quite* exact
M

[PaulE]

If you find the Shimano part number and do a Google search for it, you will find it for sale at one of the more obscure UK websites (e.g. not Probikekit, Wiggle, Chain Reaction, etc.). But it will be more expensive than just buying the complete rear derailleur. At least that is what I found when I thought my rear derailleur cage might have been bent. I bought another RD and found out the one I had wasn't bent!

[stien]

I'd like to echo Dave here and say that it's worth trying before purchasing anything else. You might have to physically remove the RD, take the B screw out and thread it in from the other side to add that last little bit of length. Or just get a longer one.

[onsight512]

thanks all.

[j_gantzer]

Until 11spd Shimano cage length only dictated chain wrap capacity and had nothing to do with max cog size.