The sway bar has alot to do with it. My 3" would be OK on the street, but at the track it would make contact with the end link bracket ( mounted to the axle ). I also have the HR bar, and have it positioned to give me the most clearance. I know that a 3 1/2" or 4" would be a problem on my car. When I do my 4", I'm not going over the axle unless the pipe is ovaled. Brian