Actually Id leave as is. The front had never rubbed till the car was slammed to the ground in meaning no air in struts whatsoever And it rubs only when turning..Actually it will make the fender move. I'm sure factory tires would do the same. As for the rears Id be more afraid of rubbing the lip then the inside plastic. Its only plastic not metal and no sharp edges. I wouldn't even go 5mm if I were to use a spacer smallest possible. Really its so tight that even a different brand tire may be sized differently. These tires were straight off a Nissan GTR and the bridgstones tend to run wide so I'm told