377rich

I am looking at getting some 8j or 8.5j rims but I am unsure of how much arch rolling will be needed or if it will be enough, I have lowered the car already on 18s to the point the arch is just above the tyre but am thinking of dropping it lower on the new rims, any advice?

Hi guys, first post on here and was looking for some help. I picked up my IS200 recently and one thing from when I first got it was that the front windows wouldn't fully lower, I took the door card off and I found the previous owner had fitted himself some new front speakers, that didn't fit properly and doesn't allow the window to fully descend, I am looking for some original speakers and thought if there are after-market ones I might as well have a look. If anyone can point me in the right direction i would really appreciate it.