I have a problem on the rear of my focus In that I can wind up the saddle on the drivers side and the car still sits 5mm lower than the passenger side??

All the saddles and rubber donuts the springs sit In seem fine could It be the spring on that side has gone softer?

I know that perhaps they wouldnt need to be cock on adjustment wise from side to side but this seems way out??

Any views greatfully excepted..

Lee