I have never heard of 40/31.
If this is it, that is 48/31.
https://www.specialized.com/us/en/di...arbon/p/175285
But I find 31 to be a bit odd, I expect even numbers on chainrings since they almost always are. Maybe a typo and 48/32, as that would have a difference of 16T and a lot of front derailleurs are designed for a 16T difference.
My low gear when I did Pacific Coast was chainring 24, big sprocket 32. I like that better but I had my camping gear on the bike.