[eakins]

building up a FS bike (Rocky Mtn Element) w/ XT m770 components (shifters, RD, chain & cassette,) & deore cranks (m590 - 22-32-44).

i own 2 FD to chose from. both are the same tube size and swing type.

the 760 is XT grade with a wide cage mount, but it's a generation before, is heavier than the 570 and also the space between the cage (where the chain is) sure is narrower than the 570. it also have rubber around the tube clamp portion.
Shimano Deore XT (FD-M760) front derailleur | VeloSpec - bikes and components specifications

the 570 is LX grade, lighter w/ a wider cage spacing (looks like it needs to move more to make a front ring shift change vrs the 760), but is a narrower cage mount to the clamp portion.
Shimano Lx Fd-M570 Front Derailleur (034750018200) at CambriaBike.com

both say mega 9 on them.

which is the ideal one to use?

thanks, bill

 

[Aresab]

I'd go with the wide link one, it should have a stiffer cage. My M760 and L M580 's look eerily similar so not sure what has changed in the new generation. Also, the M760 should be top or bottom pull, but the M570 has a top or a bottom pull config, but not both if I recall.

 

[eakins]

thanks. yes that LX M580 looks exactly like the XT M760, but not surprising since Shimano moves technology downline over the years. weight is the same.

http://velospec.com/components/shimano/fdm760
http://velospec.com/components/shimano/fdm580

guess that also says the 760 design works.