So this may or may not be a dumb question but hear me out:

So my Fat bike when I originally got it was spec’d with a 36-22 chainring and an 11-36 cassette. This was manufacture spec (I.e. from Specialized) so I’d assume they would check and see if a 36-36 combination was “useable.” I changed out the 11-36 to an 11-34 due to issues with the cassette body and I have been running that for the time being.

Now I am planning on running my bike 1x10 instead of 2x10 and I purchased a 30t narrow wide chainring and I plan on using an 11-40 cassette that I had on a different wheel. Based on what I mentioned previously, I will be going from a max chainring at the front from 36t to 30t (-6t) and the max cassette from 34t to 40t (+6t). Also I checked the cassette with my rear derailleur and it is long enough to clear the 40t sprocket.

So in theory, because the change in size in the front chainring is similar to the change in size of the rear cassette (-6t/+6t), would that mean that the chain that I have now would be long enough to work in a 30/40 combination of a 36/34 combination worked previously?