I have a Shimano LX crank with 44-32-22 rings on my commuter (set up road-bike style). BCD is 104/64. It shifts really well front and rear.

Rear cassette is a 9 speed 12-26.

I'd like to change ONLY the big chain ring to a 48 - or even a 50 (if a 50 is even available in that BCD. I know the 48 is). Can I simply change the large ring to a 48 (or 50) and leave the others as-is? This would be my simplest/cheapest change and is really all I want to do. Or would I need to change the middle ring as well - or all three?

The other two chain rings suit my purposes just fine, so I don't feel a need to change them. Other than expense, it wouldn't bother me to change them as well, but only if it's necessary to make the shifting work with the 48 or 50.

I've thought about a cassette change, but the 44/11 would not be appreciably better and don't want to buy a new cassette.

Please don't advise to learn to pedal faster - I really just want to know if the big ring change is workable.

Thanks for any help you can give.

26T jump may be more than your FD can handle. I believe triples have around a 22 tooth max. capacity.

FD capacity numbers tend to be conservative, although I have no experience to say if a FD rated with 22t capacity would handle 26t or 28t diff between small and large chainrings.
If you have bar-end shifters (so, non-indexed front shifting) you could put on FD with higher capacity.
But that would already be getting into territory where you'd be spending as much as just buying a cassette with 11t small cog.

I'd say, mount your FD as high as you can (that will still not bump the chain in the small chainring) and see how much space you have above the large chainring teeth. This will give you a sense of whether you could update to 48t or 50t large ring.
If not, just get a new cassette with 11t cog.

The difference between your big and middle chainrings is already 12 teeth. I would not increase the size of the big ring only. You could probably increase all three rings by 2 teeth and still have good shifting. Or you could increase the big and middle leaving the smallest at 22, but the shifting might suffer some. I would not do it any other way.
Is it possible? Yes. A good idea? Not in my opinion.
A cassette starting with an 11 would make more sense.

Thanks for the advice. I looked at the Sheldon Brown gear calculator and a 44X11 would be exactly the same as a 48X12. I might try to dig up a 11t cassette instead.

???

typo - corrected 44-11 = 48-12

I am building a rig right now and have a choice of two cranksets I have lying around. Whichever I use will have only the big ring when installed (1x9): A 42t and a 44t. To address your question, the reason these cranksets are lying around is because when I bought the bikes, I immediately replaced the stock MTB cranks with trekking cranks (48-38-28). With a 12-25 cassette, I still spin out on hills, although only barely. If you go from 44t to 48t, the difference will be marginal. To test this theory, I rode my commuter to work tonight on the 42t ring (it is a tall double, 52-42-30 with the 30t removed). Aside from descents, it was awesome.

Unless you are strong enough to spin out on flats on your 44-12, it may not be worth your time. I don't spin out on flats on 42t because of the freaking headwind that follows me around

I'm running a 46/34/20 on a touring bike with a Shimano Tiagra front derailer. No issues with shifting at all. I'm also running a 44/32/20 on a mountain bike and it shifts fine also with an XT front derailer. Both shift just as well as my commuter bike with a 48/36/26 crank using an Ultegra front derailer (which isn't nearly as good a triple derailer as the Tiagra).

I would caution Camillo to not use a 48 or 50 with a 32 middle however. It will shift fine but the jump between the chainrings would be very large and not that pleasant to ride.

There are a ton of 9sp 11-25 and 11-26 cassettes out there.

I found my lightly used 11-23 9 sp cassette that I thought I had given away and will put that on this weekend. I'll gain a little high end from 44-12 to 44-11 (which I need) but lose some low end from 22-26 to 22-23 (which I *think* I can afford to lose; I've been "practicing" using only the 23 as my lowest gear in back for the toughest hills on my commute).

If it's still unsatisfactory, I'll start looking for a good used stock-configured crank with larger rings and ebay this one.

Thanks for the advice.