Is it okay to use the same size tire on all four corners?
for example,

205/55/16 on all fours or
225/50/16 on all fours

 

Assuming the tire in question would fit on both front and rear wheels (which are different widths, btw), it would work, but why would you want to do this? You'd completely mangle the handling characteristics of the car.

 

Tedow is correct. Unless it is for serious snow traction I would see no other reason to do it.

Jim