(Careful to get at least 8.5 wide & 35 offset, so the stance is similar, since stock wheels have 8.5 & 29, anything less will be more inward and less aggressive. This is why I went with 9.5 wide & 35 offset, this gives me a 7mm wider stance, and room for 275's once the stock tires are shot.)
No offense to the original poster in this reply (from last year), but I don't believe that's accurate (bold and underlined emphasis are mine). For two wheels of the same width, a larger positive offset number will move the mounting surface (the inside of the wheel) further towards the outside edge of the wheel, thereby moving the entire wheel further inboard
when mounted (and not outboard).
In this example, keeping the stock 8.5" width and going from a 29mm offset to a 35mm offset will move the wheel's mounting surface 7mm further towards the outside edge of the wheel, thereby moving the entire wheel 7mm inboard
when mounted (versus stock). Now, 7mm is only about 1/4", so it's a small change, but 35mm offset wheels will sit 1/4" further inward than stock at the same 8.5" width. If using the same stock tires, the total wheel track will be about 1/2' narrower than stock (1/4" on each side of the car) with a 35mm offset than with a 29mm. A lower
positive offset number (i.e., mounting surface closer to the centerline of the wheel) would actually move the wheel outward. A 22mm offset, for example, would have the opposite effect of a 35mm. It would move the wheels about 1/4" further outward than stock.
To the original poster's credit, though, when you change the wheel's overall width
from stock, it can
change offset requirements (both for desired stance and for fitment/clearance reasons). A 9.5" wheel is (obviously) 1" wider than stock. By going to a 35mm offset with the 9.5" wheel, the mounting surface of the wheel was still moved about 1/4" (7mm) further towards the outside edge of the wheel. Offset is offset, it's measured from the wheel's centerline and doesn't care about wheel width (that's where the backspacing measurement comes into play, as it does
change with overall width). Anyway, the 35mm offset moved the 9.5" wheel 1/4" inboard over stock, just like it did for the 8.5"... BUT the wheel itself is 1" wider overall. So, with 9.5" wheels at 35mm, 1/4" of the extra 1" width is going to a wider stance and 3/4" of it is sitting further inboard (versus stock). A 9.5" wheel at the same 29mm offset as stock would put 1/2" of the extra width on each side of the wheel, if that makes sense (1/2" going to a wider stance and 1/2" sitting further inboard, versus stock).
Brake caliper clearance (as has been mentioned elsewhere in this thread) is also a factor to consider, but that's more about the design (and diameter) of the wheel than it is about offset. Offset is just moving the entire inside of the wheel further inward or outward in relation to the centerline of the wheel, so it doesn't usually have much to do with caliper clearance until you get into really extreme offsets.
Changing offsets and wheel width can have an impact on scrub angle, too... and therefore on the car's overall handling characteristics. For more on that, and/or what is probably a better explanation of offset than I just gave, see the link below (I've no affiliation to whoever this is; just found the link).
My first post here. I just today committed to a '23 CT5-V that's built, but currently in "delayed" status (likely awaiting a chip or two).
Understanding wheel offset might seem intimidating at first, but it’s actually really simple. Here’s everything you need to know about offset & backspacing.