Need some new rear tires - How much wider can I go?

[colonelburke]

I need new rear tires. I have a 2008 550i with the sport package. The wheels are 19" and the OE tires are 275/30-19s. My car is on the stock sport springs, no aftermarket lowering.

What is the widest I can fit on these wheels?

Anyone have any success stories?

Some brands are a little wider than others even though they may read the same size, does anyone know which brands tend to run a little wider than advertised?

Thanks in advance and let me know if you need more info.