In general, if you are keeping the 16 inch stock wheel size, as you decrease the sidewall by 5 you want to increase the width by 10 to keep about the same circumference so the speedometer works correctly. So 235/50 or 245/45, for example. What you then have to watch out for are two things. First, you do not want to get too wide for the wheel, that is getting the sidewalls at an angle instead of more of less straight up and down. The tire manufacturer will indicate a range of wheel widths that the tire is designed to work with, and you should not go past that range. Second, you need to make sure that the tire does not start to contact the strut. As you get wider, your margin there decreases. From my past experience with this, the 245/45 is as low and as wide as it is possible to get with the stock wheels, and only one tire was made at that time (a long while ago) that was in that size and still in width range for the OEM wheels. It was a Bridgestone, but I do not remember the model number.
Anyway, those are the things to look out for. Depending on what is made these days, you might find it simpler to go to 17 inch wheels to find a selection of possible tires, though you will still need to keep both of the above limitations in mind.
pax, smn
