I have a triple crank 50/39/30 with a Shimano 12-27 cassette. As I looked at the gear ratio chart at sheldons web site, I like the range of gear ratios I get if my 30T was a 36T instead. Example, if i was in
my 39/17T and I change to the 36T chainring it has the same ratio as 39/19T or pretty close to it.


***39T**36T
12 ---6.4 ---5.9

13 ---5.9 ---5.4

14 ---5.5 ---5.0

15 ---5.1 ---4.7

16 ---4.8 ---4.4

17 ---4.5 ---4.1

19 ---4.0 ---3.7

21 ---3.6 ---3.4

24 ---3.2 ---2.9

27 ---2.8 ---2.6

The 19T and 21T and sometimes the 24T is what I use for hills. I have at times
used the 27T but pride keeps me from it.

So is it possible to have a 36T chainring as a granny? The guy at performance says it can only be used as a middle chainring gear. I would have to do a lot more shifting to get to the gear I need when I approach the hills by using the 30T. Jumping on the 36T say a half mile or so away getting into the correct gear when I'm at the base of a hill is just a matter of downshifting into my 15T or 16T clog. When I hit the top all I need to do is go back into my 39T and I'm rolling hard again.I hope you guys understand my objective with this.

The smaller BCD on your triple crank is probably 74mm, you can go as large as a 36t with a 74 BCD, and as small as 24t. Sheldon's got 36t TA rings in 74 BCD: https://sheldonbrown.com/harris/chainrings/74.html#36

You would end up with-
50-36-30
Those tooth increments are-
14 & 6
Triples work much better when the tooth counts are in more "even" increments. like your current 11 & 9 tooth increments.
You can probably get it to "work", but expect shift quality to be worse.