Fill in wheel gap by lowering the car not changing tire sizes and for the lower profile tire thats your choice but it will mess up your speedo plus will cost more and look funny. I would look at wheels with a bigger diameter like 18s and more aggressive offset to get the lower profile tire and stance you would get with spacers. And I wouldn't run 245/55 or 50 on stock rims. Imo it looks goofy with all the sidewall.

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