Originally Posted by averagewhiteboy
And are you safe to run the 5mm spacers on the rear wheels for the 04 BBS's with stock lugs and lugnuts?
Don't know about the spacers, maybe someone else can answer. I will however explain what I mean using your example. 225 is the tire's width in millimeters. 18 is obviously the the wheel or rim size. The 40 is the aspect ratio, which refers to sidewall height. However, it's not automatically 40 mm or anything like that. What the aspect ration means is that the 40 means the sidewall height is 40% of the width (225 mm). So in this case, the sidewall height is ~90 mm. Yes, obviously this does kind of go along with tire height, however, it's not quite that simple. For example, a 225/40/18 will be shorter in overall height than a 265/40/18, and the sidewall would be taller too. This is why a 205/50/17, a 225/45/17, and a 225/40/18 are all just about the same height tire overall.