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Ultegra Di2 RD-6870 Rear Derailleur

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Electronic 11 speed goes affordable.

Shimano's Ultegra Di2 6870 Rear Derailleur doesn't rely on cable tension, indexing and a spring to control rear derailleur shifts. Like their flagship Dura-Ace Di2 unit, an electronic worm drive is used to eliminate the pull and pull-back associated with a derailleur spring and cable. Once properly set up, the digital derailleur shifts across the available 11 cogs with ultimate precision every time.

In the event of a crash, a saver function allows the derailleur to move in towards the wheel and away from the force of impact. Then it automatically resets itself with the push of a button and a few gear changes. If the auto reset fails, a manual reset is possible via buttons on the battery harness module near the stem and handlebar junction that work much like a barrel adjuster for fine tuning.

Limit screws are still set manually, but once they are locked in, it's smooth sailing (and shifting). Slightly larger internals add a few extra grams compared to the Dura-Ace Di2 11 speed model while significantly lowering the price.

The RD-6870 is available in a SS version with a max cog size of 28t and GS version for up to 32t. Sold as derailleur only with no cables.

Note: The RD-6870 is compatible with Dura-Ace Di2 9070 11 speed components.

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Excellent RD that extends cassette range support
by Anonymous
Cycling Enthusiast
0 of 1 customers found this review helpful.

I'm not sure why bike mfrs supply only the short cage versions of this RD when cost for SS and GS versions are essentially the same. The GS extends the range of cassette cogs that can be used from 28T with SS to 32T with the GS. Unless of course there's a conspiracy afoot..... ,-)

Reviewed 5/4/2017
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Allows you to go from an 11-28 cassette to an 11-32 cassette on a Dura Ace DI2 road bike.
by mgearing
Cycling Enthusiast
Portland, OR

Wanted to have an 11-32 cassette for long andor steep climbs. Replacing the Dura Ace DI2 rear derailleur with this was super easy. Now I can climb at a much higher cadence.

Reviewed 1/8/2017
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Easy upgrade to 11-speed Di2
by John Mess
Cycling Enthusiast
1 of 1 customers found this review helpful.

I converted my Ultegra 6770 10-speed to 11-speed. All you need is an 11-speed chain, cassette, and RD. Swap out the parts and upgrade the firmware to 2.x (if needed) and you have an 11-speed. An 11-speed crank works the best but a 10-speed crank works well enough.

Reviewed 3/10/2014
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