Discuss light weight issues concerning mountain bikes & parts.

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by xcfisher

Anbody know what Ceramic Speed OSPW is being used on this GRX Di2 Rear Derailleur? It looks like perhaps its the new version intended for the Ultegra/RX Di2 rear derailleur? I wasn't aware they shared the same cage mounts. I like the way this looks, and functionally it could open up the possibility of another option for a lightweight MTB Di2 setup with a clutched RD. I have never been a fan of the XTR Di2 rear derailleur, I have always thought it looked 'bulky'. I'm curious what the max cassette size could be used with this type of setup.

by Weenie

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by TerryDi2C

hmm, interesting! Keep in mind though that you cannot mix Di2 MTB and Road derailleurs (GRX counts as a 'road' derailleur).

If you use a front derailleur and a rear derailleur they must both be road or both MTB derailleurs. Of course if you don't have a front derailleur then go ahead ;)

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by IrrelevantD

Looking at the EV and DM docs for the RX800/805 and RX810/815 RDs, my guess would be it's the same as the one for the Ultegra RX (RX800/805). Unless there is a difference in where the location of the plate stopper pin screws in, or the hole for the plate tension spring, it probably isn't going to be that different. It's entirely possible that the changes between the RX and the GRX is so small that "close enough" is good enough to make it work.
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