If you meant to say you have 235/50-17 tires, then they're an inch taller then stock.

The offset wouldn't cause this, unless it is much lower then stock - on a 17x7" wheel, the offset would have to be below +35 (give or take a couple mm) for the tire to get anywhere near the edge of the fender.

By all means, make sure your suspension is up to snuff, but I'd look into getting correctly-sized tires before jumping off a bridge and trying to fit "other Subaru model" suspension components.