Link: http://www.bmwpartswheels.com/bmw-wheels-33/

If you own a BMW and are still riding the stock 16's or 17's, why not upgrade to larger BMW wheels which will bring you better performance and much improved looks. The wheels of a vehicle are the most important aspect of its look. Bigger wheels also provide better handling and improved response.

Examples of sizes you can upgrade to:

All 3 series: Recommended to go with up to 19 inch wheels for maximum performance.

All 5 series: Recommended to go with 20 inch wheels for maximum performance and aggressive looks.

All Z3/Z4 we recommend either 18 or 19 because they are small cars.