The brief
The 318i had developed a soft knock over speed humps, the steering felt vague at motorway speeds, and the inside edges of both front tyres were starting to feather. The car was telling the owner the front geometry was no longer being held properly.
The front suspension on this car uses a set of aluminium arms per side to locate each wheel, each one carrying rubber bushings and ball joints. When those wear, the wheel can shift a fraction under load: the slack gives the knock over bumps, the geometry drifting makes the steering feel less precise, and the misalignment that comes with it scrubs the inside edge of the front tyres.
The diagnosis
A pry-test on the front arms showed the rubber bushes deflecting well past the service limit, and the ball-joint boots were starting to split. The arms on the other side were the same age and heading the same way.
On a multilink front end the labour to get in there is much the same whether you do a couple of arms or the set, so doing the lot, the worn arms on both sides, was the call that made sense rather than going back in soon for the next ones.
The work
The worn front control arms came off both sides, and a full set of new BMW-spec front arms went on with fresh bushings and ball joints, every bolt torqued to spec with the suspension at ride height so the bushes settle in their neutral position.
Then the car rolled onto the alignment rack for a full four-wheel alignment, camber, caster and toe brought back to factory, with the before-and-after numbers printed for the owner.
The outcome
The knock over humps was gone, the steering tightened up and tracked straight, and no pull.
The 318i went home steering the way it did when it was new. For the owner that is a car that feels precise and planted again, plus, with the geometry restored, front tyres that will wear evenly across their tread instead of feathering on one edge, which is a full set's worth of kilometres saved.