ok i took off my rear tires to paint my drums today and the belt is starting to show on the one. the fronts are about two months old.(i bought the rims and tires new and the guy replaced the front ones right before i bought it) heres my problem. i currently have 225/35/18 toyo proxes on it front and rear. i want to go to 225/40/18 i wanted to know if i could get new ones for the rear that are 40 series while still running 35 up front. also does anyone have an opinion on the khumo ecstas(sp.??) they are pretty inexpensive and i was wondering how they were. thanks guys

It depends on the tire place, some places won't put different size tires on your car, others don't care. As for the Kuhmos, I know mnay people have had good luck with them, but personally I think they suck. My h-rated yokohamas perform better than my z-rated kuhmos.

my cousin owns a shop so i will put them on myself i just want to know if its harmful to run diff. sizes

No you aren't going to hurt anything, it may look a little weird and I don't know how/if that would affect handling. Basically I would get them all matched up as soon as possible.