I have weighed in before on the 3x9 question with regard to cross chaining. I tried every variety of 3x9 combos I could think of and finally the reality struck me. I was always looking at my total range of gear inches and then the total usable gears without duplication and keeping the smallest steps possible. Although the start and stop points of the range are important what is most important is the gear inch you are in when on the middle ring and the middle cog.

That should be your happy place IMO. I then wanted my gearing to radiate out in both directions on the cassette off the center ring like I was riding a 1x9. I consider the granny ring a completely different bike and the size of that ring can be whatever you need for the hills where you live. I always looked at that gearing as a 1x6 or a 1x5 range and never plan on using the outer 3 or 4 cogs. Once I set my gearing up like that I pondered long and hard what do I need the big ring for?

I was about to take it off and replace it with a bash ring and be mostly happy with a 2x9 when the old idea of half-step came back to me. I knew 42 was my magic number for a middle ring in the front and 12-36 with a 21t cog in the center of it was my happy place. I played with the calculators and found 45t was to be my new big ring as it gave me 6 new GI’s spaced perfectly in between my center ring GI’s.

I set the bike up like that and gave it a go and was very pleased and surprised by a couple things. The first being how easy the shift was in both directions going 42/45. Every bit as easy as a one cog shift in the back. The second and most impressive thing I didn’t expect was how good the straighter chain line felt off the big ring on the 3 smallest cogs. That and the fact I dropped from a 52t to a 45t made those gear much more likely to be used.

I have a 24t granny on now but I hung on to the 30t and the 26t. My bike is a tour bike that mainly gets used around town. I could see a person putting the 24t on to tour and normally use a 30t for commuting as the shift is a bit easier.

I love having the in between gears. I don’t shift up the half-step pattern like the old days. I just run across the cassette like it was a 1x9 but if the wind changes a little or the grade changes a half shift let me keep my cadence and effort constant and in effect gives me gearing like I had a 1x15 with granny without cross chaining.

Here are my numbers. 45-42-24 X 12,14,16,18,21,24,28,32,36
My Granny without cross chain will give me this GI range. (6 gears)
17.7
20.0
22.8
26.6
30.4
35.5

And my main rings with half step will give me these without cross chaining. (15 gears)The ones shown with the minus sign are the new half steps off the 45t.
31.4
35.3
40.4
47.1
- 50.5
53.9
- 57.7
62.8
- 67.3
70.7
- 75.7
80.8
- 86.6
94.3
- 101.0