Originally Posted by
Marcus_Ti
Actually, no. You need an entire new crankset.
Physically, the smallest circular rings a 110BCD will permit are 33T...although you can squeeze out 32T if you get very creative and accurate/precise machining (As in Praxis Works 48/32 cranks). To get 30T you need a smaller BCD (as in say Sugino or IRD cranks), or use direct mount rings of some sort (FSA). Your standard Hollowtech cranks--as of now--do not permit 30T circular rings.
This is what caught my eye while I was researching my post--https://bikerumor.com/2018/01/09/climb-anything-new-absoluteblack-46-30-48-32-micro-compact-chainrings/---no idea on the cost, but I bet, more than i would want to pay but less than the cost of a new Red ETap crank set.
Whoops, i should have scrolled down ... "Prices for the 46T/48T are €105/95£/124$ and for the 30T/32T 76€/67£/87.5$." So about $250 for the rings alone? Ouch.
I wasn't planning on doing it anyway, but thanks for pointing that out.