So I searched around the net and have gotten mixed answers. I have a set of 255/35/18 tires. and an 18x8 wheel. I know its prefered to put this tire on a 9" wheel, but will the tire fit on an 8" wheel?

 

It will be a little pinched, but physically will fit.

 

Even being a 35 series tire? The search i did came up with the same answer but was for a 40 series.

 

That won't make much difference and a 255/35/18 is the proper profile to keep stockish tire diameter. Auto-x guys stuck with stock wheels have run wider tires than that, it's a compromise but you can do it.

 

The shorter sidewall helps because it will deflect a bit less, which is the biggest issue with too wide a tire for the rim, but it will still be pinched so expect less then optimum handling, certainly at the limit.

10" wide rim is the optimum width for a 255 fyi. 9" is the most popular because it’s the easiest to fit on the car. Not because it performs better.