The tour will be in Europe...so I am not too concerned about spare parts; particularly as the cassette and the chain will be Shimano. I own almost nothing Shimano/Sram (no Shimano specific tools either) but I still have a ton of Campa 10speed stuff which I want to put to good use. I do, however, get on in age (wrong side of 50) and would really like to use a 40t or at least 36t cassette. Particularly as the tour will be rather long and I will have at least 35kg of luggage. Hence, the question. As regards the crank...It's a Campa 10speed CX with 110BCD. It comes (or rather came) with standard 36/46 chainrings. I have the shift mate because I intend to use a Shimano spaced Ali Express 11-40 cassette. Opinions differ as to whether this (Campa ergo+campa rd+Shimano Cassette) works without Shiftmate or not; we'll see. If the the rd with wolf tooth won't get up to 40t (according to their website if used with Shimano/Sram it goes up to 40t but they "recommend" only 36t for the Campa setup) I will have to buy a sub-compact crank. Which I am not too keen on because of vanity, male pride, ego etc. ;-)
I suspect that the recommendation of 36t for Campag vs 40t for Shimano has more to do with the max chain wrap capacity of Campag RDs vs Shimano. It's not in Wolftooth's best interest to recommend the use of a 40t cassette for Campag when the Campag RD won't handle the chain wrap inherent in such large sprockets. According to Branford bikes, 10sp Campag long-cage RDs have a nominal chain wrap capacity of 39 teeth, although in my experience these numbers are conservative and you can go a few teeth over. By that reckoning, your proposed 11-40 cassette and 36/46 crankset (chain wrap 39) should work fine. However, for loaded touring, whatever gear you think is low enough - go lower, because you'll ultimately need it. With your proposed setup, your lowest gear will be 0.9:1 (1:1 with the 36t cassette) - IMO that's nowhere
near low enough for pulling you, your bike and
~80lb of stuff up hills (and if it can carry that load, you're probably not talking about a particularly light bike to start with). I'm not saying that you couldn't do it on any given day, but day after day? You need gearing that won't require you to bury yourself at any point, so you can keep doing it. You
really need lower gearing.