1. Usually weight. They're lighter than steel wheels. Also, there's less restriction to the design of the wheel (as opposed to the plastic wheel covers which are supposed to.. well cover the steel wheel)

2. it *may* increase handling but it will decrease FE (either b/c it's heavier than the stock wheels or aerodynamic reasons cause it's larger)

3. no idea. I'm not a wheel expert, sorry!

4. No idea... I only know Yokohamas and Toyos as the performance-oriented tyre brands.

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