Should you be able to so a straight swap over ultegra di2 6870 to a 8050 RD

Hi

Bought a Ultegra RD-8050-SG di2 rear mech to replace a Ultegra 6870-SS di2 mech so a bigger cassette can be installed on the better half’s road bike (and to have a spare mech)

But when di2 cable is plugged in it does nothing , old mech still works when plugged back in

I’m guessing its to do with firmware version not up to date (But i dont have the gubbins to do to that) – or should it just work when  plugged in and i’ve managed to buy a faulty mech

So any thoughts on whether i have a faulty mech or i have to get firmware upgraded..

thx

You need to reconfigure the system. Some of it can be done by computer and some of it needs the app.
You of course have already checked the compatibility chart of Di2 components?
https://e-tubeproject.shimano.com/pdf/en/HM-CC.3.0.0-01-EN.pdf

all compatible – apart from not having a SM-PCE1 unit to connect to computer to flash firmware and devices – £160 for one of them !!

Anyone in the Brighton area got one i could borrow ?

Had this before when i used to build Di2 bikes for a UK distributors team riders

More than likely the new mech has a newer firmware than the old one

What i found is that if all components were version 5.2 or 5.7 etc… they all would communicate fine but if one component was version 4.2 or 4.7 etc… then the whole system wouldn’t work and you couldn’t update the component which was version 4.2 using e-tube and plugging into the junction box

I had to use the SM-PCE1 interface and connect the individual component directly to e-tube to update it, then once connected back on the bike’s system i ran e-tube via the junction box and the system worked fine

I no longer have my SM-PCE1 interface but im sure you can rent them on ebay

https://www.ebay.co.uk/itm/Shimano-SM-PCE1-PC-Interface-Device-for-hire-4-DAY-hire/223860572084?epid=1037624324&hash=item341f213fb4:g:uxkAAOSwbsBXj3IJ