I wanted to try Shinko 705 110/80-19" front and 120/80-18" rear tires http://www.bikebandit.com/shinko-705-motorcycle-tire
...and I even asked another forum member here(who uses the radial 110/80-19" both front and rear on a different type of bike) how wide they were as to if one would fit between a `71 CL350's forks which he said "absolute widest part mounted is almost exactly 4 inches (3.98 or so)"...and it seemed that would squeeze in
...as I really wanted something that would work well on gravel roads
but I chickened out, thinking thats just too much tire on the stock pretty thin rims
instead I got Shinko 712 100/90-19" front 110/90-18" rear on the stock rims
http://www.bikebandit.com/shinko-712-motorcycle-tire
....its pretty common to see this size combo of tires on a CB/CL350(I have another CL350 thats had that size on it for years before I got it) but thats as wide as i would ever go on the skinny stock rims, and its probably pushing it alittle