Description Reviews MINI Cooper and MINI Cooper S gen 1 front sway bar. The Cooper bar is 22.5mm and the Cooper S bar is 24mm. Water can get trapped in between the bushing and the bar causing it to rust and expand. When too much rust is in there it causes the bar to bind. Or it starts to fall out which makes the bar smaller, which in turn makes a clunk during normal driving. Under performance driving it will cause scary handling. Its a good idea to look at this problem before doing the control arm bushings. Also don't forget the bushings!