Mountain Bike Reviews Forum banner
1 - 11 of 11 Posts

·
Registered
Joined
·
44 Posts
Discussion Starter · #1 ·
I have been looking at these two models of Shimano rear derailleur and I can't really see a difference. Is it difference in model year? Seems like Shimano keeps adding more and more model numbers to confuse everyone. :)
 

·
Registered
Joined
·
599 Posts
The M781 is the "direct mount capable" version. This means the bracket axle assembly (the small plate between the main pivot point and the RD hanger - sometimes also called a 'B2' assembly) can be removed, and the the main pivot point screwed directly into a swept back RD hanger.

It's a modification Shimano have quietly introduced for all their 2013 mechs, but which has received a less than enthusiastic reception by the industry, with only a few of the more niche bike builders using this capability. You might find it more widely adopted in the future though as more bolt thru rear axles appear on bikes.

If your bike has a 'normal' RD hanger then it essentially makes no difference whether you get an M780 or M781. The M781 will work in both modes, so you're a bit more future proofed, that's all.

If you want to see what one looks like in "direct mount" mode, then click here Rotwild 2013 - 650B Enduro und weitere Neuheiten von der ISPO Bike and page down to photo no. 9. Notice the swept back RD hanger, and the absence of that extra little plate between the RD hanger and the main pivot point of the RD (and yes I know thats a shadow+ RD, but it was the only picture I could find of a direct mounted RD, and the principle is the same).
 

·
the catalan connection
Joined
·
1,266 Posts
I´m trying to figure out the image thing. Mines always come with the "attached images" frame on them....:confused:
 

·
Registered
Joined
·
15 Posts
The M781 is the "direct mount capable" version. This means the bracket axle assembly (the small plate between the main pivot point and the RD hanger - sometimes also called a 'B2' assembly) can be removed, and the the main pivot point screwed directly into a swept back RD hanger.
That's not a real difference though, right? Can't the B2 assembly can be removed from the M780 for direct mount as well?

Is the real difference only that now direct mount hangers exist, and updated instructions/marketing? Or is there an actual substantial difference I'm missing?

-Daver
 

·
Registered
Joined
·
599 Posts
That's not a real difference though, right? Can't the B2 assembly can be removed from the M780 for direct mount as well?

Is the real difference only that now direct mount hangers exist, and updated instructions/marketing? Or is there an actual substantial difference I'm missing?

-Daver
Yes, its a real difference, albeit a minor one.

You are correct you can remove the B2 link from the M780 as well, but what you'd be left with is a gap in the mech body too narrow to fit a rear hanger, and a bolt too small to bolt into the threads on a rear hanger (tho I guess there's nothing to stop you machining your own custom rear hanger to fit!).

So essentially the difference is that on the M781 they've made the interface between the main pivot and B2 link the same specs as the interface between the B2 link and the hanger, so you have the choice of attaching it to a hanger at either point.

Major manufacturers have been slow to bring out the swept back rear hangers though, so even though bikes are coming out with M781s on them, they're nearly all still using the B2 link attached to conventional hangers. My guess is they're waiting to modify the whole rear dropout at the same time as they introduce bolt-thru rear axles.
 

·
Registered
Joined
·
1,435 Posts
Both are Shadow and 10 speed. So its just the hanger.

You guys realize Shimano does this on purpose right, its unlogical to the regular public but in Shimano's mind over in Asia its 100% logical.

How would you compare XT M786 Shadow + to the XT M781 Shadow?
Both are 10 speed.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top