The brief
The owner described a soft knock from the front over speed humps, steering that felt vague at motorway speeds, and a small pull on rough surfaces. A quick check of the front tyres showed feathering on the inside edges, the giveaway that something underneath was not holding the geometry properly.
Those four things together, the knock, the vague steering, the pull, and the uneven tyre wear, all point at the front lower control arms. They locate the bottom of each front wheel, through rubber bushings at the chassis end and a ball joint at the wheel end. When the bushings perish, the wheel can shift slightly under load: hence the knock from the slack, the vagueness from the play, and the tyre wear from the alignment drifting.
The diagnosis
On the lift, we pry-tested both front lower control arms. The bushes on both sides showed visible deflection well beyond service spec, and one was split and torn right through, the rubber so far gone you could see daylight in it. The ball-joint boots were starting to split too.
Replacing one and leaving the other would have left a mismatch in stiffness side to side, one corner firm on a new arm, the other still slack, which makes the car feel worse, not better, and the old arm fails soon enough anyway. So it was a pair job, both front lower arms, with a four-wheel alignment afterwards because the geometry will have drifted while the bushes were collapsing.
The work
Removed both front lower control arms, then fitted a matched pair of new Audi-spec replacements with fresh ball joints and bushes. Every bolt torqued to spec, with the bush bolts taken up at ride height so the bushings settle in their neutral position rather than pre-twisted.
Then the car rolled onto the alignment rack for a full four-wheel alignment, camber, caster and toe brought back to factory across all four corners, with the before-and-after numbers printed for the owner.
The outcome
No knock over humps. The steering tightened up at speed, the vagueness gone. No pull on rough surfaces. Alignment back in spec.
The Q3 went home steering the way it did when it was new. For the owner, the obvious win is a front end that feels solid and precise again. The quieter win is the tyres: with the geometry restored, the front tyres will wear evenly across their tread instead of feathering away an inside edge, which is a full set's worth of kilometres rather than a premature replacement.
And a fresh pair of arms gives the front suspension years of service rather than a return visit.