I used 285/60-18 nitto terra grappler as my first tire on a factory 18x8. no rubbing and it fit fine in spare space with that shield removed.
No rubbing up front on stock bumper/fender liner, but it's possible the tiny difference in offset allowed this. 53 on an 8" vs your idea of 45 ET on an 8.5" which will be wider both due to offset by 8mm and also due to the wheel adding 1/4" more to the outward face. for example, if you had an 8.5" ET 53 wheel, it's added width for clearance concerns would be 1/2 of the extra width, so 1/4". So, take 6mm + 8mm and you've more or less added 14mm to where the swing radius will occur during turning.
Due to the same reasons, there could be contact of the inside edge of the upper rear fender flare/liner during 100% compression. Maybe not, but it will be close.
Don't put a 285 on a wider offset wheel on your vehicle though thinking you'll decide then because it'll look so cool you'll talk yourself into using it no matter how bad the rubs are
Proportionally, the 285 is the line where tires look seriously awesome on the lr3/4 body style especially if flush to the fender flares.
I don't have rubbing on mine but they are 275/65-18 on an 8" but also with a 25mm spacer. 285 is quite a bit wider though and mine has all the mods needed and an aftermarket front bumper which allows more room.
Consider that in almost all off road situations and surfaces, a narrower taller tire will perform better. You can fit a 265/65-18 no problem. You can do a few mods and use a 265/70 or 275/65. 285 gets you no performance off road actually, just looks.
A taller narrower tire will make a long patch when using low psi and crawl onto things rather than how a wide tire will tend to push stuff in front of it. Proportionally speaking of course. We can't fit massive wide tires that are also proportionally tall and with a huge long patch when aired down.
If you think from a view of maximum patch area, our vehicle with it's limitations requires the skinnier but tall approach.
I know you're trying the 8.5 because it's one of the few easy bolt-on 18" choices. Just know that both measurements are reducing the maximum allowable size because both aspects push the outer edge further out than a factory 8" with ET 53 so you'll have to compromise with either the width or height unless you do certain mods to the vehicle.
I would expect 265/65-18 to work but just barely on that 8.5" wheel and offset. Surely someone has a compomotive with exact tire to give feedback.
