No, unless you want to switch your current shifters into 'friction' mode (assuming they still make them with that capability).
Grab a 105 11 speed rd, and a set of shimano 11 speed tt shifters.
Oh, of course then you'll need 11 speed wheels.... :)

Your best bet is to go on ebay and just grab another 10 speed rd, tons of them on there!

https://www.performancebike.com/shop/shimano-ultegra-ice-grey-rd-6700-ss-rear-derailleur-50-8463


https://www.bikeinn.com/bike/shimano-ultegra-double-rd-6700-10s/135996726/p?utm_source=google_products&utm_medium=merchant&id_producte=2685355&country=us&gclid=Cj0KCQjwgMnYBRDRARIsANC2dfmAs2n2pMv4nHCgUojb4SaLDSzAf_kVVSb9w8JeoRsBgGN1NYaLX8YaAhEvEALw_wcB&gclsrc=aw.ds




28 cassette will work great with either of these. That's exactly what I run.

I agree with your recommendation, but not with your explanation. I´m pretty sure the 11 speed rd works with 10 speed cassettes and shifters. The 10-speed shifters pull slightly more wire which moves the rd slightly more for every "click".

No, the pull ratio was changed with 11s.

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The problem you are not realizing is that the rear derilleurs themselves have a different movement ratio between 10 speed and 11 speed......different geometry in in parallelogram if you will...or the angle that the cable pulls on it from, or something like that..

Its possible you might be able to fudge it and get it working 'OK', but on paper it is not supposed to work..

This page has an in depth writeup of how it all works...

http://blog.artscyclery.com/...train-compatibility/

NO!!! 11 speed Shimano derailleurs have a different geometry than the 9 and 10 spd ones (which were identical to each other). So you need a 9 or 10 speed derailleur. 105, Ultegra, or Dura Ace, all the same.

I have some Dura Ace derailleurs (2 9spd and 1 10spd) I'm not using, if you are interested.

Short cage should work fine for 28t and 50/34, though that is the limit.

Thanks for the advice.

I didn't even think about Performance Bike, I have a coupon code so I am going to pick up that 6700 from them for a little more than the 105 I got off Amazon.

Good call, it's the cable pull ratio that matters... Shimano 10 vs 11 is different, but SRAM 10 vs 11 is the same... I have a SRAM 1x Rival Clutch RD paired with a 10 speed TT shifter, works fine. Same RD is 11 Speed capable...

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i can sell you a lightly used ultegra 10sp RD cheap - pm me if interested.

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Thanks! I went di2 for 11 speed, so I guess I´m a bit out of the loop.

so, this falls into the "learn something new everyday" -- i had thought, and may now be mistaken, that the "shift" was in the shifter, NOT the RD (or fd) and the SHIFTER moves the amount, not the RD .. btw, it does work IRL, even if not supposed to work on paper -- i've had 5800 and 6800 RD on 10 speeds with zero trouble .. repeat, zero -- i THOUGHT the RD had a range of movement (high and low) that are defined by the limit screws, and the shifter does all the work ... again, i could be totally wrong (and expect to get flamed) but it's worked just fine, on 4 bikes, for me ...

though, I will keep it in mind next time i have the chain off the 10 speeds