Uhhh, wheel width plus offset, and tire size matter. Asking for which spacer without providing wheel width and offset, or tire size may result in responses that will mislead you.
I ran 8mm spacers with the 18" oem wheels(18x7.5 @ 50'ish ET) and it didn't rub. When I switched wheels to 18x8 @ 45 ET, it rubbed under hard cornering...while always running 225/40-18 rubber.
For height reference; this all was when it was suited with Eibach Sportline height but with the new 18x8 wheels, a rear H&R ARB, and no spacers ↓
Because there was no rubbing without the spacers, I was able to drop it even more;
With a straight edge and some measuring...you can figure out how much more you can poke the wheels out. Same process can be used if and when you ever decide to swap the wheels to a different width and offset or tire width...but by using your math skills.