What size spacers do i need to get flush with staggered LTW's? I currently have 12.5mm on the front but I want to put those on the rear and maybe get some 15mm for the front. Tire sizes are stock (225/45/17 and 245/40/17)
Flush is subjective. You can't get that last few cm of fitment because of your spring rates and tire sizes, but if you just want to fill out the fenders a bit more 20mm front will do the trick. The 12.5mm is fine for the rear, depending on how rolled your lips are.
8.5s all around would look A LOT better, of course. Especially with some 235/40s and more spacing...okay I took it too far.