well what size rim do you have now? most makes of tires use the second number as a height of the tires. so 215/40/18's are pretty low profile any lower then that and you have to worry about bending rims and you will notice a big difference in the ride quality.

 

i got 16 inch rims

 

well with out making your rims look tiny i would say go with 45 or 50's

 

you should be running 205/55-16s on a 2G Eclipse.