RIght now I have the gnx wheels on my rear with no spacers, I have the 255/60 tires and there is about 1/2 inch on both sides between frame and tire sidewall. My car sits straight. I dont know the back spacing on the gnx type wheels.
What GNX wheels do you have?
Are they the GTA mesh wheels or the GBody mesh wheels as the offset and backspacing are different.
Are they 16”x 8”?
A 275 tire is 3/4” wider than a 255, so 3/8” more on each side.
To move the tire away from the frame 3/8” you’ll need 3/8” less backspace than you have now. If you have more than 3/8” clearance to the frame don’t worry about it.
Assuming you have an 8” wide wheel now.
Going from an 8” wheel to a 9” wheel will move the tire closer to the fender given the same backspacing.
There should be an offset number stamped into the backside of the wheels you have now.
Here’s a chart that will help.
I have to draw it out so it makes sense.
This is a different setup, but a good example.
How wide are your wheels now and what’s the offset number?