17's wont get you better traction per say though,
i'm running 215's all round , ran 245s on the front for a set and by fook it got off the line but handled horribly.
I am running ET 37 with spacers atm and it is scrubbing a bit too much (the roads over here are horribly rough)
I think I will roll the arches a fraction and tak 1-2mm off the spacers and hopefully that will solve the issues (or i could just jack the car up 5 mm
If I where you i would look into tyres before wheels, whats the max width you can put on the super T's?