# New RD (6870 or 8050) with 6870 groupset?



## RoiH (Aug 11, 2012)

Hi everyone - first post so go easy one me ;-)

So I smashed my rear derailleur on my 6870 Di2 Shimano groupset. The bike is a Trek Madone 4.9 2014. It has the external battery and the M-EW67 junction. Not sure which junction is inside the frame.

I want to replace the RD with either a RD-6870 with as little hassle/cash as possible - or prossibly a RD-8050, since it can handle bigger cassettes.

So here's my questions:
Can I replace the broken RD-6870 without updating firmware on all compontents? If I have to update firmware on all components, what's the cheapest/easiest method of doing it?

Can I upgrade the RD to a 8050? 
If so, what do I need to do with respect to firmware and HW?

I've checked out the compatibility chart, see attachment, but I find it a bit confusing.

I'd really appreciate your advice! 

Cheers,
Rói


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## Marc (Jan 23, 2005)

RoiH said:


> Hi everyone - first post so go easy one me ;-)
> 
> So I smashed my rear derailleur on my 6870 Di2 Shimano groupset. The bike is a Trek Madone 4.9 2014. It has the external battery and the M-EW67 junction. Not sure which junction is inside the frame.
> 
> ...


Firstly..use the latest E-Tube compatibility chart...the picture above is 2 years out of date:

http://e-tubeproject.shimano.com/pdf/en/HM-CC.3.3.2-00-EN.pdf

See Page 3. It isn't that hard to read. It tells you what you what you can and cannot use.


Now in your case you are going to have some headaches. Do you own a PCE1 device to update firmware with? The debugger costs $150USD, and is needed because of your ancient battery and ancient Junction A box. I'm going to take a wild guess that your bike hasn't been updated in 4 years....so to even talk to the new RD you'd need to update everything. Most bike shops don';t even own a PCE1--because of how rare Di2 rigs are.

The above comes to maybe $350USD between the PCE1 and the RD (whichever you get)

Another option instead of buying the PCE1 debugger and RD...is update your Di2 network.....which costs more money now, but makes for less headaches later, presuming you plan on keeping this bike longer. Which means:

-New RD (either 6870 or 8050)....Maybe $200 depending on what you get.
-New Junction A. Either SW90A or B, or MT800, or well any of the newer ones...about $90USD
-New cabling for JunctionA to brifters ($50USD)....the SW67 had integrated cabling the SW90 and other new Junction A do not have cabling included.
-New charger/USB interface BCR2 that is "only" $50USD.
-New battery (DN100 or DN110)-$130USD

Which....Comes out to $500 to bring your Di2 network current.


It needs noted that the newer Di2 functionality like Synchronized Shifting *will not work without the new battery* (DN100/DN110) _which itself requires_ the new Junction A and some cabling. The *cheapest *method is to just buy a 6870RD while you can....you can buy a Wolftooth RoadLink to use larger cassettes with the 6870 or any other road RD---I think a Wolf Link is $22USD+shipping these days. You will probably need a new chain as well as whatever larger range cassette you want


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## rcb78 (Jun 15, 2008)

Marc said:


> Most bike shops don';t even own a PCE1--because of how rare Di2 rigs are.


LOL,, you must not live where I live. DI2 is more common than many people think. All the shops that I'm in contact around here have at least one guy that is pretty well versed in working with DI2.

OP, call the shop where you bought the bike and ask what they would charge to do firmware on you bike. Most places quote between $20-$40 depending on if you bought the bike from them or another shop. I'd be pretty let down if a shop selling DI2 doesn't have the means to support it. A PCE1 is cheaper than half of the decades old tools hanging on the wall where I am.


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## tlg (May 11, 2011)

RD-6870-GS Medium Cage will do 32T. $175

https://www.merlincycles.com/shiman...NPK9z39jUVRoopv7VH_ILsRUo793YxyQaAnzsEALw_wcB


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## cxwrench (Nov 9, 2004)

Marc said:


> Most bike shops don';t even own a PCE1--because of how rare Di2 rigs are.


What? You're kidding,right?


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## Marc (Jan 23, 2005)

rcb78 said:


> LOL,, you must not live where I live. DI2 is more common than many people think. All the shops that I'm in contact around here have at least one guy that is pretty well versed in working with DI2.
> 
> OP, call the shop where you bought the bike and ask what they would charge to do firmware on you bike. Most places quote between $20-$40 depending on if you bought the bike from them or another shop. I'd be pretty let down if a shop selling DI2 doesn't have the means to support it. A PCE1 is cheaper than half of the decades old tools hanging on the wall where I am.





cxwrench said:


> What? You're kidding,right?


I'd have to cross state lines at least once. No shops in my state capitol have to pce1... Would probably have to drive to Kansas City to even find one.


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