Alright I just purchased another Evo and it's on 17x10 +18 RPF1's. Now I'm looking at trading a guy for some 17x9.5 +38 because I don't like how far the +18's sit outside the fender. From reading, I need at least an 18mm spacer so I ordered a pair of Ichiba 20mm spacers. After thinking, if I go with a +38 offset with a 20mm spacer, doesn't that put me right back at the equivalent of the +18 offset? I suck with wheel specs so am I correct or no?

Thanks,
Anthony

 

Yes. It will be the exact same nominal offset. But the wheel will sit further inside the fender by -0.25" because the 9.5" wide wheel will be 0.5" narrower than the 10" wide one. And half of that wheel width difference affects the offeset measurement from wheel centerline.

See also:
http://www.1010tires.com/Tools/Wheel-Offset-Calculator

 

^^^ Yup.