Suspension Knock

[R32Abuser]

MODS: I started a topic in General maintenance but, in hindsight, this topic is better suited to this section. If required, please delete/close my thread in "General Maintenance".

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

[GTSBoy]

One loose disc and one tight is not an issue.

Your first idea on the bonnet may be valid. Wind up the bonnet rubber in the front corner of the radiator support panel. They do tend to wind themselves down, and then the bonnet can flap a little. Worth a try anyway.

If it's in the front suspension, then it is possible that it is the ball joint at the bottom of the upright, or the bushes in the upper arm. These are common wear points. The other leading suspect is just a worn damper.

[Duncan]

Firstly, you are right, the disc is floating. So the fact one moved a little and the other didnt is just random and not your issue.

Also worth noting that pretty much any bush/balljoint etc problem won't really turn up just by a push by hand. What you really need is to get a big pry behind them and try hard to move them. Keep in mind each of those bushes regularly holds 500kg+

By far the most likely cause of the noise is your suspension strut. They all have a nut on the top which can cause a knocking if they loosen up. Get a rattle gun onto it and see if it is tight, it should be easily accessible on the front (rears are a different story). You can't tighten it with a socked because the whole shaft will turn

[R32Abuser]

GTSBoy: Wound them up. Will drive the car to work tomorrow and see if it has helped. Worth a try as you have said. Come this weekend, Ill put her back up on the stands and check the lower upright BJ. The upper arm bushes looked fine but as Duncan pointed out, nothing is magically going to move around by hand.

Duncan: I would like to give this a try but unfortunately I dont have a rattle gun. Will have to see if I can borrow one.

So neither of you think it could be the wheel bearing? Im dubious but you never know!!!

Edited May 29, 2012 by R32Abuser

[GTSBoy]

Could be, and they are all at the right age to be dying (if not replaced already). But in my experience, R32 wheel bearings don't make a lot of noise even when rooted.

[Duncan]

agreed...it's not impossible it is a wheel bearing, but they are a damn good design and wear very well, even under track use. eg I am still running the original factory ones in the race car. Usually, wheel bearings only make a noise when they are the loaded side, so you will hear it from the outside in corners.

It is at least 10x more likely to be the suspension top nut. It is really hard to pick visually when it is loose because the spring almost always has some preload on it, making it look tight.

DEpending on the shock you may be able to tighten it with hand tools - some have an allen key socket on the top, or a small flat on the shaft to put a spanner on to stop it turning. If so you are in luck

[GTSBoy]

It is at least 10x more likely to be the suspension top nut. It is really hard to pick visually when it is loose because the spring almost always has some preload on it, making it look tight.

That's one I missed and also probably the most likely. It also leads to the damper f**king up properly too, because of the rapid bump start and stop for up-down strokes as it flies free then stops suddenly against the bottom of the strut or against the nut at the top.

[R32Abuser]

IIRC my Sydneykid bilsteins have an allenkey socket in the tops of the shaft. Could definately be wrong though as I haven't looked closely.

Looks like I'll be searching for a rattle gun ASAP haha

[R32Abuser]

OK so the Bilstein from sydneykid's kits have an allenkey socket in the top of the shaft which meant I could hold it still whilst tightening the nut. This was all done with the shocks in the car. The left side definately didnt seem "loose" but had about a turn in it until it was proper tight. The right side probably had about half a turn.

So I took it for a drive and the noise is still there but its incredibly sporadic. Sometimes it will make the noise so easy over the smallest of change in the road surface. A minute later, it won't make a noise at all over small or large deviations of the road surface. Weird huh?!

One thing i did notice as I push down on the inner guard with the car stationary, is that when it did make a small knock sound, it sounded as if you had tapped the spring with something and the vibration continued for a brief moment. Like a free spring resonating after you tap it! This makes me think its definitely shock related.

I've been meaning to take my whiteline springs out of the Sydneykid setup. The spring rate is good but I simply do not use the extra spring rate and could use a little more ride height. At 345 front eyebrow height, the guard bottoms out on the tyre from time to time on big dips.

Might get some custom springs made up - similar spring rate to the current whiteline items, but with a longer length for more ride height.

Edited May 30, 2012 by R32Abuser

[Duncan]

ok...+1 point to Gary's Bilsteins for having the allen key bit...makes that a lot easier.

Is the knock exactly the same, or better, since tightening?

The next most likely place for a knock is the top mount itself. As they wear, they allow movement between the shaft and the strut top/mount.

Do you re-use the original strut tops, or put in an aftermarket/pillow ball top? You may need to replace them.

Next most likely is a suspension arm bush, probably the top arm bushes. Get a long pry bar behind them and see how far they move when you push them, hard.

[GTSBoy]

Next thought is the collar nut that holds the damper into the strut body.

[R32Abuser]

ok...+1 point to Gary's Bilsteins for having the allen key bit...makes that a lot easier.

Is the knock exactly the same, or better, since tightening?

The next most likely place for a knock is the top mount itself. As they wear, they allow movement between the shaft and the strut top/mount.

Do you re-use the original strut tops, or put in an aftermarket/pillow ball top? You may need to replace them.

Next most likely is a suspension arm bush, probably the top arm bushes. Get a long pry bar behind them and see how far they move when you push them, hard.

If anything it happens less often, but the severity/amplitude of the noise is still the same.

Yeh I reused standard the original strut tops. Would want to retain this setup since most pillowball setups increase NVH a bit. My car is for street duties so would rather keep this to a minimum.

I reckon I could just re-order all the standard shock bushes etc. from Nissan and replace all of them if need be.

I think this weekend I'll remove the front shocks. Considering it takes all of about 5 minutes per corner once the car is jacked up, I think its worth it to inspect the shocks. This will also allow me to check all the bushes in the front end.

*Sigh*... Least Ill get to try out the standard springs.

Next thought is the collar nut that holds the damper into the strut body.

If I disassemble the shock, I'll check for this.

Edited May 30, 2012 by R32Abuser

[R32Abuser]

Ok just for those playing at home...I have found the knock and solved the issue.

A while ago, I changed the standard drop links in my Anti Roll Bar setup to Whiteline's "heavy duty" items.

Amongst my worry to get all of the "pre-load" out of the roll bar setup, I did not completely tighten one side of a drop link. This then allowed the sway bar to move laterally in its mounts when the bar was actuated (over small/large bumps or deviations).

A quick go with the spanner and "hey presto", the noise is completely gone.

Edited September 2, 2012 by R32Abuser

[GTSBoy]

Typical. It's never what anyone thinks.

This is why Whiteline have the lock kit for anti-roll bars. (Lock kit being nothing more than some polybush material and a couple of hose clamps, I might add, but nevertheless!) Stops the bar moving across the car.

[R32Abuser]

Yup. Story of my life...Oh well least its fixed.

Yeh I have seen those, specially for Subaru bretherans IIRC.

Now I just have to get my arse around to doing my diff/rear end overhaul. Nothing better than a clunky as hell diff round shitty Adelaide streets