Noticed about a week ago a quiet hum as the S2 got up to speed, but I didnt think much of it as I thought it might be clutch or g'box related which both are getting replaced very soon.

On Tuesday the hum suddenly became louder and sounded more like an unbalanced wheel spinning (imaging the wheel wobbling slightly).

From about 15mph you can hear it, and the faster you are going the louder it is. From about 40mph it becomes more of a loud knocking like someone thumping at a door, then the knocking gets faster and faster until its a humming sound at around 60mph.

I've noticed that the knocking sound is at its loudest when the wheels are pointing forwards or to the left. When the wheels are pointing to the right its a lot quieter.

I got the car up on 2 troll jacks, and got the wheels rolling. A mate was listening for the sound from the engine bay ... couldnt hear anything from there at all, but the wheels were wobbling slightly (which I think the problem might be). I can feel the hum/vibration through the steering wheel most of the time, and sometimes through the pedals (more so the brake pedal). The car also feels slightly odd when turning left at speed, not sure how to explain it, almost like the wheel isnt gripping anything or is moving slightly (in a way it shouldnt).

I was going to pop into the local tyre place and see if they can balance the wheels just to see if its that.

Anyone else got an idea ?