Originally Posted by
MiPeGr
Would that mess with shifting? Either with the deraileur due to the big # of tooth jump between middle and inner, or with the ramps and pins?
I run a 9s Deore M590 crankset with 48-36-22 for the same reason. It works fine for me. Specific Sheldon Brown's page on FD:
https://www.sheldonbrown.com/front-derailers.html He says that
surprisingly, the size of the "granny" chainring has little effect on derailer performance. Many cyclists customize their "road triple" cranksets by installing a more-useful smaller ring in place of the 30 that comes stock.
You may encounter some problems with low/absent chain tension in low-low gears which you should not be using anyway (insufficient RD capacity). For example, I have M591 RD, which is rated for 45t wrap capacity. The front difference is 48-22=26, rear is 34-11=23. The total is 26+23=49, which slightly exceeds 45. Not a problem for me, YMMV.
Edit: when shifting from the middle to the granny ring under some load, the chain may drop. "Dog fang" chain catchers can help.