Well Ed, I guess there's nothin' like a pictorial to shed a little light upon a subject, eh?!
Yep, my feelings in this regard are I wouldn't do this "modification" on a friggin' bet, 'cause there IS a reason why they make car tires AND motorcycle tires, and THAT pictorial you've just supplied us here would be one Reason No.1 why I wouldn't "place a bet" on MY life while tryin' to save a few bucks in the short term!
(...of course I can now hear the next reasonale for this pictorial from the "Car Tire/Save A Few Bucks Crowd" around here: "That guy just doesn't ride very well!"...riiiiiight!...well, in THAT case, just LOOK how much friggin' rubber is contacting the friggin' road in picture No.1, folks...but HEY, do what cha want here...as far as I know there are no laws, other than maybe the Laws of Physics, against doin' this...and I'M certainly NOT gonna contact MY congressman about it!!!)
