Replace 6870 Di2 with R8050

teebs_123

Hi All,

Purchased a R8050 Di2 rear mech to replace an old 6870 Di2 one. I have removed the old unit and gone to screw the new one onto the mech hanger. The screw goes through ok but doesn't seem to bind onto the other side of the mech, almost like the alignment is out by a few mm.

I've scratched my head and searched high and low on the net but cant find a solution..

I'm probably doing something stupid, any ideas?

Thanks.

i.bhamra

When you line the bolt on the mech up with the hanger are you sure the tab on the back of the mech that butts up against the rear of the hanger to stop it rotating to far forward is clearing the face of the hanger? You need rotate the mech backwards a little to make sure it clears it otherwise as you start tightening it up it will foul the hanger and prevent it tightening up.

Sorry if this a) is not very clear or b) so obvious to you already that it's an insult to your intelligence!!

rafletcher

It's confusing (I don't mean teh post above!) but if you look on page 44 of this...

https://si.shimano.com/pdfs/dm/DM-R8050-03-ENG.pdf

you should be able to work it out. As IB says, there is a tab on the uppermost part of the mech, and this tab neds to be "behind" the back of the hanger.

teebs_123

Thanks chaps. I might've solved it - I have removed the additional "hanger" from the new mech. Is this supposed to stay on (the frame is a 2016 S-Works Tarmac with a standard "hanger" still in situ)?

I did install it initially with this on, but it looked as though the mech was too low..

rafletcher

Yes it is supposed to stay on, it allows the mech to sit a bit more "inboard" and is supposed to help prevent damage - I think!

ETA - quote from a retailers website

"The Di2 (RD-8050) rear derailleur (RD) adopts the Dura-Ace low-profile Shimano Shadow RD design to sit fully under the cassette, tucked away from potential damage. "

teebs_123

Balls!!

Cheers, will give it another shot - it did seem to sit really low compared to the previous mech...