I've got a 46/30 and 11x34 on my gravel bike and I have never once regretted having the 34. Some day I may mullet the bike and go even bigger. I live in a fairly flat area but still regularly see 10+% on gravel. Granted it's never anything longer than 30-60 seconds but it's nice to have the biggest gearing possible.

My cross experience is limited, but for actual cross racing - it is often quicker to run sections where you might want a lower gear than the 28 would give you.

Maybe a bit. You're certainly overthinking the last part. Once you have the right tools, swapping cassettes is a few minute task. If the race course calls for tighter gearing, just swap back to the 11-28. A GS "mid-cage" derailleur (there really aren't SGS "long cage" road derailleurs) will shift an 11-28 just fine, even if the chain is a few links longer than optimal. My bike came with an GS RD and an 11-34 cassette, but it's quite flat locally so I ride with a 12-27 cassette most of the time. I keep that 11-34 handy, though, in the event that I travel someplace hillier. I didn't take any links out of the chain, so going between cassettes requires only a B-screw adjustment and sometimes a fine-tuning of the RD cable tension. Shifting has been just fine on the 12-27.

For cyclocross/gravel, I would recommend a clutched rear derailleur like an Ultegra RX or one of the new GRX, especially if you're going to run an 11-28 with a chain that has enough links for a 11-34. If you were really doing it right, you'd have a specific chain for each cassette that had the optimal number of links for that cassette. For a couple races a year? I personally wouldn't bother.

As for whether an 11-32 or an 11-34 would be better, it's a tough call. The 11-34 has at least a 2-tooth gap on every step, while the 11-32 has single-tooth gaps for the 4 tallest gears. It comes down to a couple questions. 1st, are you a cadence slave, only comfortable with extended pedaling in a fairly narrow cadence range? 2nd, are you looking to maximize your performance all the time, intent on using the cassette for racing or for hard group rides that are a real challenge for you to keep up with? If the answer to both is "Yes," get the 11-32.

If you can pedal as easily at 65 rpm as 95, or you can just back off a touch without fear of getting dropped by selecting the lower gear when you find yourself "between gears," and you want the lowest gearing possible to extend your capacity to climb, it's the 11-34. Or spring for both, and have 3 cassettes at your disposal to cover a broad variety of situations.

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"They're made of latex, not nitroglycerin"

My current ride is a 46/36 up front and a 11/34 in the rear.

I can get up most climbs in a 32, but if there is fresh gravel, that 34 comes in handy pretty quickly. Gravel roads tend to be steeper as well. So I recommend 11/34. If i could I would go 46/30 in the front.

I've been on some really steep inclines on a tough gravel course where I live that hits above 15%. My Aspero came with a 47/32 and an 11/34 in the back. First time I rode the course I had no problem spinning up those climbs in a 36/34. Switched to a 50/34 so I could have a power meter, and was still fine for the most part but not spinning as much.

I don't know many people using identical gearing for both gravel and cyclocross. 'Gaps' in gears means nothing to me in cyclocross because it is so rare that I'm holding one gear for very long.....except in single speed.

I don't think you will regret the 11-34 for gravel. Maybe drop down to a single ~40 tooth 1x ring for actual cyclocross season and stick with that 11-34. I'm a mid pack cat 3 in CX and find there's still some times I'm pedaling in a 32 rear around people running.

you can play around at https://www.bikecalc.com/speed_at_cadence to see what the difference is that you're looking at.

With a 700x35c tire and pedaling 60rpm in your 36t front ring, you're looking at 5.5mph with a 32t rear or 5.15mph with a 34t. The difference is pretty tiny between the 32 and the 34.

The bigger difference between the cassettes will be where the "missing' cogs are, and that depends a bit on which 11-34 cassette or which 11-32 cassette you buy.

My .02 - I don't like the shimano 11-34 cassette that has steady jumps throughout the range: 11, 13, 15, 17, 19, 21, 23, 25, 27, 30, 34.

I prefer something more like this: 11-32: 11-12-13-14-16-18-20-22-25-28-32

I'd rather have small jumps at the bottom and big jumps at the top. At the bottom, i can really feel the gap. At the top, you feel it less. But i would bet you'd feel the missing 12t and 14t more than you'd feel a difference between a 32 and 34.

Gearing is really dependent on how strong you are.

I was comparing gears with the winner of a really hilly triathlon and he was crushing an 11-25, whereas I could barely get up the hills with an 11-28.

I put on an 11/36 (50/34 up front) for a hilly gravel ride last fall and the difference was noticeable - walked a lot less than I did on the same course in 2018. Also added a SRAM GX2.1 RD so RD capacity wasn't an issue.

Just got a set of 46/36 rings to see how they affect things, but haven't installed yet.

Pretty funny that just before I came over to ST I just placed an order for the long cage and 11-34T. I have never regretted the larger gearing and when I would go to Europe on my 10 year old Orbea with a 10 Spd I would throw on a MTB derailleur and a 36 for the 15-18%+ stuff we would hit and it would keep me from burning matches and try to save legs as much as possible as we were riding 100k+ for multiply days with 2-3000m of climbing. Don't see any reason not to go to the 32.

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I miss you "Sports Night"

On a steeper hill, the difference between the power needed to maintain 5.15 and 5.5 mph might be more than you'd think. On a 10% grade, it's around 7%. Depending where the power requirements are relative to your threshold, and how long the climb is, that 7% could be significant. If I look at my power curve, there's ~7% difference between my 15 minute power and my 30 minute power.

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"They're made of latex, not nitroglycerin"

Interesting, I'd have to say my experience is that I would much rather have smaller gaps towards the top of the cassette. I find myself a lot more picky with cadence when climbing, especially at lower speeds. Big jumps when you're grinding up a climb drive me mad. I also find having smaller gaps near the top of the cassette helps off road with maintaining traction. If I can keep my cadence in a range I'm comfortable with, I find it easier to finesse power output on sketchy/ loose climbs.

a wolflink ($30) might be cheaper and as effective as a long cage rear derailleur. i had standard/short 105 rear derailleur and the link allowed me to go from 11-28 to 11-34.

as for cassette, it really depends on the terrain you're riding and strength. i'm in areas with lots of hills and use the gravel bike like a mtn bike. with some trails with pitches >10% grade, i'm wanting even more gearing (currently 46/36, 11-34)....or stronger legs! :-)

I would go to a 30 small ring up front, then an 11/32 in the back. You can get that by using your current derailment and reversing the b screw.

Maurice

Thank you all for your thoughts.

I think my preference all along was to have a Cx bike that I could ride some Gravel with, instead of vice versa. (For the record, I am going to be sucking it in the middle/rear and running no matter what cassette I have)

I think this fits the most with my thinking. I prefer, and am most comfortable when maintaining a steady cadence. And I do prefer to push myself by racing, going hard with a group, or just trying to beat my own previous time on any given local ride.

I think the 11/32 as my main set-up makes sense. I did discuss going with a long cage derailleur with a clutch. So also like to idea of simply having an 11/34 to switch to when doing bigger gravel rides with legit climbs.

I have played around a lot with a similar setup. My main conclusion was that the 46/36 combo is a bit of a hold-out from a previous era when the main concern was dropping chains. With modern mechs and cassette options there are better options out there.

Personally I found the 46/36 a flawed mashup of 1x and a 50/34 compact. The problem with 50/34 off-road is that you will often find yourself in extreme chain-lines but in reality the 46/36 doesn't improve this situation much. And for the minor improvement in chain line you have to make a noticeable sacrifice in gear spacing on the cassette to cover the same range. Going 1x solves the chain line issue and you can do this without needing massive gear jumps. It is super easy to change front rings on 1x so you just optimize the front ring for the course. The downside is a loss in overall range but its not that big relative to a 46/36.

Given you want a CX bike first I would go 1x with one of the wolf-tooth rings designed for a Shimano 2x setup. Something like a 38t paired with a 11-32 cassette. If you ever decided to do any really gnarly gravel events you can then go back to 2x.