Can I use a 11-23 11-speed Shimano cassette with the RD-R8000 11-speed Ultegra Shadow rear derailleur (short cage)? I would like to know whether I can use a 11-23 11-speed shimano cassette with the RD-R8000 11-speed Ultegra Shadow Rear Derailleur (short cage).

I ask this question because I see the new 11-speed Shimano cassettes no longer come in a 11-23 gearing.

Looking forward to your comments.

Thanks
Probably you'll be just fine, although it's technically outside the spec'd range.

Per the Shimano 2019-2020 Products compatibility Information document (warning: PDF link), the RD-R8000 rear derailleur is compatible with all of the following cassettes:

CS-R9100
CS-9000
CS-6800
CS-5800
CS-R8000
CS-HG800-11
CS-R7000
CS-HG700-11


As far as I know, that covers all of Shimano's 11-speed road cassettes, and I'm assuming Shimano doesn't produce an 11-23 MTB cassette.

BUT

The RD-R8000 is spec'd as

    RD-R8000-SS
(25T≤CS Low gear≤30T)


(the GS is similary spec'd with a 28T minimum)

so a 23-tooth sprocket would be slightly too small per Shimano's specs.

But it should work for you as Shimano's spec's are notoriously tight - and I already do have an 11-23 on a bike with an RD-8000-SS and it works fine with an 11-23. (I didn't even know it wasn't "in spec"...)

The page the info was extracted from: