Wheel Size?

I have been hearing some scraping noises coming from the tires. I took it to a local car shop that didn't spec in bimmers and they said that the tires were either too wide or too large (dunno how wide they are but they are 16" rims) What is the max size tire i should have on these rims? I personaly think that i need new shocks and i did buy these tires not too long ago, but i don't remember hearing the noise when i first got the tires. Anyone have any ideas?