metalheart44

I am replacing a Di2 6870 front derailleur with an 8050 front derailleur. I believe there is only one braze on adapter --SM-AD91-- for either the Di2 front derailleurs, but I am not sure about this. I do not know what the part number is on my existing clamp/mount/ adapter, but I am assuming that I can just remove the 6870 derailleur and use the existing clamp/mount/adapter for the new 8050 derailleur?

sennder

Your current band adapter will probably not work. The new FD design (braze on) has a support bolt that pushes against the frame to provide further stability. You have to use it with the band adapter as well. The SM-AD91 adapter has a little notch to allow the support bolt to get a good grip, which the older adapters do not. You can look up SM-AD91 on google image search to see what I mean.

--Sennder

metalheart44

Thanks, that is very helpful, much more so than the local shop that did not have a clue.....

metalheart44

Update: I talked with a Shimano tech support person this morning and asked if my existing adapter -- SM-AD67-1 -- would work or if not then what is the part number of the adapter I need. The technical said that the existing adapter should work just fine.

metalheart44

Checked with another source that builds bikes everyday and they indicated that the Shimano tech was incorrect. For my bike, the 8050 front derailleur takes a different adapter clamp, the SM-AD91-L (the size that fits a 35mm seat tube.)

sennder

Technically, you could use any standard band adapter as long as it fits the derailleur and the frame. You don't have to use the support bolt. But the derailleur becomes a lot more stable with the support bolt installed.

Do update the thread on what you ended up using and how it worked.

--Sennder