Force needed for tire and rim (removing/inserting) Until now I used 26" rim with Schwalbe Fat Frank and Big Apple (range 2.15"-2.35"). Except for initial prying when removing tire I can perform all operations with my bare hands without a sweat.

Today to my surprise I literally fought to remove WTB Resolute 42C from the rim (28") and risked breaking the tire lever when inserting back Specialized Sawtooth 42C tire.

Why such difference? Is it old vs. new? Wide vs. narrow? Or is it just this particular tire against other one and there is simply no rule.
There is a small acceptable range of bead diameters for a given rim size, hence some tires are a little bit loose, some are tight.