Just to clarify, I wasn't worried about the wheel rubbing, rather it was tires. A 10" ET25, as a wheel, fits just fine!
Let's say we're looking at a 275/35 round shoulder tire like the PSS. On a 9.5" (tire's measured width) wheel, tread width will be about 10". On a 10" wheel, tread width will be about 10.2".
What about a square shouldered tire like an RS-3 in the same size/aspect? On a 9.5" (tire's measured width) wheel, tread width will be about 10.2". On a 10" wheel, tread width will be about 10.4".
Rated M Roadster is running a 10" ET25, with a 275/35 RS-3 on a lowered car, but is running a good amount of negative camber (
-3 rear) to keep it from rubbing. I think there are plans to
roll the rear fenders a bit and dial it back. (BTW, I think his set-up looks unbelievably good!)
Contrast Rated M's setup with that of
kennyfrc's stock setup that's running a 275/35 PSS on a 10" wheel. Kenny's is on a totally stock setup, no rubbing, no tweaks. (BTW, that's another very good looking setup).
Section width (sidewall meaty part of the tire) is the same on the RS-3 and the PSS. But not tread width. And wheel size and the tire's measured rim size affect the tread width (~2/10" for each .5" rim increment). That's why a PSS works on the 10" wheel pretty easily, whereas a more square shouldered tire might not work without some adjustments (it
will work but there is some tweaking to do).
The other thing about the increase of 1" on wheels is that the space on the front wheel well is more generous, relatively speaking, since the rear starts off at 9", and already uses a chunk of real estate. At least that's my read on the amount of available room. So the 1" change is a bigger one, relatively speaking, given the available real estate.
Bottom line, there are a lot of variables involved in fitment, as I've learned on this journey (still learning):
Tire's measured rim size
Wheel width (and impact to tire's measured size)
Offsets
Lowering
Camber (and how camber is achieved, plates vs. shims vs. lowering or a combo)
Perch location