25" marathons vs 24" knobbies (similar diameter?)

I'm trying to figure out what 24" knobby tires I can put on my extra set of wheels that would be similar enough in diameter to my 25" marathons so that my composite scissor brakes will work with both without adjustment? I'm going with 1.25" rear wheel spacing on my new TR3 to allow for 2" wide knobbies to clear my side guards when I use them.

Anyone know the diameter of either of these?
http://ift.tt/1UVf0ZA

http://ift.tt/1UVf0ZC

25" marathons vs 24" knobbies (similar diameter?)