Originally Posted by pexio

Actually you can put a smaller inner chainring on new Ultegra triple cranks but you will need a new middle ring first. As you know, with the 6703 Ultegra triple, Shimano adopted the older Dura Ace triple design of mounting the inner ring directly onto the middle ring using a proprietary 92mm BCD for which only 30t rings are available. By replacing the stock Ultegra middle ring with a Specialites TA Alize K, you can mount a granny ring as low as 24t. The Alize K uses the industry-standard 74mm BCD for the granny - not the Shimano-only 92mm. It's not a cheap ring, but it is a TA after all. I got mine from Peter White Cycles - see this page. Here's is my Alize K setup:

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This is a DA FC-7703 crank (same 130/92 BCD as Ultegra) with the stock 53t big ring, a 39t Alize K and a 26t granny. With a 10 speed 12-28 cassette, I have a nice wide gear range (which my knees appreciate riding in the Berkshires here in western MA), fewer front shifts, and tight gear spacing (one tooth jumps from 12t to 17t). Triples are great!