Knocking Sound From Front Suspension

[R32Abuser]

Before I go on, I'll start by saying yes I have searched and apart from getting some very vague posts, I am yet to find an answer.

Ok so the other week I replaced my speedo cable after it snapped, I took the car for a spin and it was all good.

Being mainly a weekend car, I drove it the next weekend and noticed a very dull but distinctive knocking noise coming from what seems like under the bonnet or from the suspension (left side if anything). It occurs randomly, but seems as though its in sync with deviations in the road, hence why I think it is related to the suspension. Smooth roads it doesn't occur, bumpy roads its far more noticeable.

Since it seemed like the bonnet may be the issue, I check tightened everything with regards to the bonnet (hinges etc.) but to no avail. The sound was still there.

So on the weekend just gone, I thought I would do some checks on the car and check tighten all of the suspension to make sure it wasn't anything loose making the knocking noise. I went through the shocks (top and bottom bolts), sway bar chassis mounts, brake caliper bolts, engine cross-member bolts, caster rod bolts pretty much everything i could get to without having to take anything major off. All bolts were tight.

Someone suggested that the issue may be a wheel bearing, so I went on about the checks I've seen for a busted wheel bearing. Now here's where it get's interesting:

Being lazy, I didnt want to put the wheel back on. So, I pulled on the rotor (with the wheel off) on the right side ( opposite side where noise seems to be coming from) and the rotor didnt move. All good. Went to the left side (side where noise seems to be coming from), and the the rotor will wiggle about up to ~5mm. However, it is only the rotor which is moving, not the hub itself.

So after doing this, I decided to put the wheels on and try. Next to no wobble from either wheel.

I then checked for tie rod movement. There is very little if any in the rod ends.

IIRC, the brake setup is a floating arrangement and there is no fastening mechanism directly between the hub and the rotor other than the wheel studs/nuts. In saying that, the rotors can become "bound" to the hub via heat, dirt etc. That being said, Im unsure why one side is able to be wobbled, and the other not.

Furthermore, the wheel bearing from that side does make a very faint metal on metal sound like a bearing is begining to go. But it doesnt seem like this is the issue, as the knocking I'm getting I can't replicated, other than the rotor wobble.

Can anyone shed some light/experience as to what they think or have found in the past?

Cheers,

David

[aussietroy]

Mine had a similar knock coming from my left hand side too only when hitting small bumps in the road and it turned out to be a worn bush in the front upper control arm, when you jack the car up can you hear a creaking/smallish knock sound ?? Im sure youd of heard it when you jacked the car up, but thats what mine was ....

[R32Abuser]

I have whiteline urethane adjustable bushes in my upper arms, so when you jack it up it makes a small squeeking noise. Has done this from the day I bought them (3 yrs ago but less than 10-15000 km's ago).

I highly doubt that its a worn upper bush. Last thing I want to do is change it aswell considering I'd have to get another wheel alignment if removed for checking. That said, its something to keep in mind I guess...