No you do not. My rims are 22in but overall they are the same as the stock 20s I had. Both the stockers and aftermarket rims are the same 5.5'' backspacing and are 31.7'' in diameter. My stock tires on the 20s were 60 in height and my current tires are 40 in height. The offset on my rims are +19mm.

[EDIT] also, I dont remember what my stock width in those 20'' tires were but Im riding 305/40/22s so my tires are wider and I dont scrub.

[EDIT 2] I see on CST site for those 4'' they say "DESIGNED TO FIT 33" TIRES W/ 8" WIDE WHEELS" and "WHEELS MUST NOT HAVE MORE THAN 4.75" BACKSPACE" but my rims are 22*9'' and like I said, 5.5'' backspacing so maybe thats just thier spindles that require those numbers.