If i buy 4 aftermarket wheels in 18 inch and put 35 inch toyo's on them can i still use my 17 rim for a spare with a 35 inch tire on it....what im saying is a 35x12.50x18 the same size as a 35x12.50x17 or do i need to get a 18 inch wheel for a spare? There both 35's but not sure if they would be exactly the same, i figure they would be but want to make sure. Thanks

 

They're the same if you order them in SAE sizes. The metric ones are the ones that change depending on rim size (complicated mumbo jumbo)

 

just make sure the outside diameter is the same, but i doubt you will get a flat with the toyo's assuming your are getting the open countrys
and as a bonus the 35 should fit in where the spare goes, unlike those gm and chevy guys