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Shimano Di2 Rear Derailleur 6870 replacement stock?

by pablo
Mon, Jun 08, 2020 17:03
7

Hi all,

I managed to damage my rear derailleur and thought it was just the lower plates which i replaced with brand new items but it appears the whole assembly has been twisted although I cannot see any damage and it indexes perfectly. I've checked the hanger using a straight edge and measurements back to the wheel and it's fine.
When you look from the back of the bike the lower jockey wheel is 5mm to the right compare to the upper (which is slightly angles) so when in a small gear the chain jumps off the jockey wheel at the bottom and when in a hi gear it won't go into the smallest sprocket you can index one of the extremes out but it makes the other far worse. I also put a none di2 derailleur on it just to check visually i wasn't going barmy.
I'm all out of ideas so think it's time I ordered a new one but I can't find any new stock has anyone seen any? I don't really want to go to ebay for a used item as they are not cheap and if somethings wrong i don't want the drama.

If you're new please join in and if you have questions pop them below and the forum regulars will answer as best we can.

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7 comments

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pablo | 3 years ago
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Ha Had a bit of a result!  I club friend of mine had a dead derailleur with a very frozen motor and said i could have it so i've taken my motor, plates, jockey wheels, and swapped them in and it works perfectly now! Still can't see where the old one was twisted.  I thought i would post this just incase anyone is trying to do similar in the future.  

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Welsh boy replied to pablo | 3 years ago
1 like

Do you know that Di2 rear mechs can "freeze" after a crash and appear to be dead?  Something like a 5 second press of the button on the control box usually brings it back to life.  Dont throw away the bits from the frozed mech, you may be able to bring it back to life.

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Pilot Pete replied to Welsh boy | 3 years ago
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Yes, five seconds until the Junction A light flashes red. Then you must turn the pedals as the rear derailleur will change through all the gears. Make sure if it happens out on the road that the hanger isn't bent as it could shift into the spokes!

PP

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Drinfinity | 3 years ago
0 likes

Definitely get a mech hanger alignment tool. I never try to fix niggling indexing problems until I've checked everything is straight.

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bobbinogs | 3 years ago
0 likes

Are you sure that you didn't bend the hanger? There are alignment checkers but spare hangers are relatively cheap and easy to swap out. If things don't improve then swap back and keep the spare safe as it can be reassuring to know that you have one packed when you are off on a bike holiday somewhere (not worth carrying on a bike though).

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pablo replied to bobbinogs | 3 years ago
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The hanger is new although it doesn't guarantee it's straight. I used the ghetto method of using a straight edge against the hanger and measuring to 4 points around the wheel rim. I even swapped in a spare non di2 derailleur to see what it looked like and it was vertical and not twisted.

I wasn't aware R8000 di2 were compatible I guess this is why you can't get 6800 looks like that's my only route.
Annoyingly a fellow club mate had a 6800 version with a knackered motor it ashame they aren't serviceable.

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jacknorell | 3 years ago
0 likes

If you don't want used then the new R8000 version will work perfectly with your other group set parts

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