Assuming your current wheels are +48 offset. The new wheels (no tyres) will stick further out by 17.7mm. Otherwise if your current wheels are +45 offset then the new wheels will stick further out by 14.7mm.

I reckon you'll be able to pull it off if you stretch the tyres onto the rim and you'll probably need to add a bit more camber in the rear.

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RS Liberty - Because WRX's are only good for parts...