I have a road bike with a Shimano 10 speed 105 group (2007). It has a triple 50-39-30 crank. I want to put a 11-36 cassette maybe the Shimano Deore XT CS-M771 10-Speed Cassette (Note: I can’t find an 12-36 cassette for sale). The way I understand capacity I would need 45t (50+36=86 30+11=41 86-41=45).
First is the shift ratio of my 2007 Shimano 105 10 speed shifters compatible with the derailleurs listed below:
The Shimano Deore XT RD-M772-SGS Shadow Rear Derailleur appears to have the 45t capacity but is rated for 34t max cog.
The Shimano XT RD-M780 Shadow Rear Derailleur SGS is rated for a 36t max cog but only has a 43t capacity.
Harris Cyclery list their Shimano XT RD-M772 Shadow SGS Rear Derailleur Top Normal as having a 36t max cog, this may be an error or what they have successfully run. They want full list price of $129.95.