make sure to check exactly where it is rubbing. i spent ages trimming/rolling my rear arches only to find out 90% of the rubbing was due to contact with the lip of the rear bumper where it sits inside the arch. i trimmed as much of this back as i could without ruining the mounting holes, and problem solved. and mine was sat stupid low on 17x7" rims, 205 40 17 tyres, and i believe et38