The shop said it was like 1/16th of an inch off, im guessing its those indents next to the holes for the studs? they suggested that a rim shop could machine them wider?

 

the center bore is bigger on the gr86/brz (56.1mm) versus recent corollas (54.1mm i think from a quick google). it's the centering circle that the wheel "sits" on. Yes a machine shop should be able to correct.

 

whenever buying wheels you should look at the offset and center bore. if the offset of the corolla wheels is too far off it may still not fit or work well, even if you get the center bore machined to fit.

 

Your Toyota GR86 is actually a Subaru; no reason Corolla wheels should fit your GR86 anymore than wheels for a Nissan Sentra.

 

That isnt really the case. There are only a few factors in wheel size that are used universally. If the bily pattern, hub bore and offset are all within the useable range for the vehicle that is all that matters. The brand of vehicle makes absolutely no difference. Do you think aftermarket wheel companies design a different wheel for every single car ever made? No, they design to sizes that cover a wide range of given widths\offsets to a particular lug pattern.
In this case all the specs match up except the hub bore size on the corolla wheel is too small. Getting them machined is one option to make them fit. Another option would be to add some bolt on spacers that convert to the smaller hub bore size. You would have to do some calculating to figure out if there was proper clearance for the lowered offset.

 

Without looking up the numbers to confirm, the offsets are likely very different. You can't just go by bolt pattern, you need to know offsets and center bore. If brakes are tight, the same size wheel of a different style can also interfere with the brakes, but that's a less common problem.

 

Old Subarus had weird offsets and unusual bolt patterns. For my early '80s GLs, the only non-OEM wheels that fit were from a Peugeot and I think there was one (ugly) aftermarket wheel in stock size, but if you wanted to upgrade to 14"s, the Peugeot was it. If there was something else, that was in the day before internet, so it was tough to find out. Anyway, it's not tough anymore—look up the wheel specs and go shopping/comparing. Offset doesn't have to be exact, but within a range. You don't even have to figure that out anymore, as someone must have put that up somewhere online already (probably on here).

 

I guess hub bore could easily be enlarged. Hell, I did it with a dremel on a set of cheap steelies, but it was something like a .5mm difference IIRC. I really wanted 14" wheels and there weren't a lot of options outside of spending too much money for a set of new steelies.

When I'm shopping OEM wheels across platforms, it's usually because I'm being a titewad and wouldn't want to pay labor to have hubs opened up. If one wants something unique or finds a dirt cheap set of wheels, I suppose machining them out is a reasonable option.