What tyre size have you got fitted and what suspension are you running?
I ran ET42 18 x 8's (same as Focus RS) with 215/35 tyres stretched on them, Koni adjustables (coilovers), Eibach anti roll bars AND Poly bushes and still got scrubbing front and rear over hard bumps.
I've also run ET37 17 x 7's with both 215/45 AND 215/40 tyres with the same setup (wound down the ride height a little bit more) and got rubbing on big bumps as well.
caprizetec - STANDARD ST170 wheels are ET49
Escow- Van - 2.0 litre 16" wheels may have 205 width tyres on them but they are only 6" wide and ET52.5 hence they are nowhere near the edges of the arches!