The air spring is a big rubber “sock” that’s inverted over a big plastic tube. It makes a very sharp turn so there’s a crease. I think you have to jack the axle up to maximize extension and then spray the treatment up inside the area where it folds. I will try to do this treatment soon and take photos.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)