Knock Sound in Rear Suspension

[jfitz981]

Hello All.

I have recently finished installing the new suspension on my S4. Finally got the correct springs and the ride height correct. Looks awesome.

I did notice on the drive that there sounds like a knocking sound coming from the rear of the car. For example, if I push down on the rear end, it makes that knock sound as I push down. Has anyone experienced something along these lines? If so, what sound I be looking for under the car.

Thanks for the help.

Jason

[Jonathan]

What shocks did you use ? Or are they original with just lowering springs ?

Could be one of a few things :

* Spacing washers left off the lower damper fixing.

* Spring not sitting right on top/bottom cups.

* Spring rubber insulator at the top not present.

* Damper lower fixings not done up tight enough (lower bush clicking on the threads).

* Upper damper fixing not done up tight enough / rubbers missing. If this is loose the top fixing will rattle as the suspension moves, the metal locating cup washers around the rubbers have lips on them which are used to locate into the top damper fixing on the chassis - these could be slipping in and out of the location.

Post some pictures, the rear suspension is very simple but there are a few things to note when putting it back together (spacing washers etc) that look inconsiquential but are actually important.

you didn't unbolt anything else whilst you were under there ?

Here's some junk off my site if that helps:

Clicky

Also my article I done for LEW

Clicky

Edited May 14, 2006 by Jonathan

[esprithk]

I think you need to do a full wheel alignments..

after you change the shocks, you have to measure and balance all 4 wheels again.

**Jonathan

your Esprit is fantastic!!

I love the repaint of the parts..(silver & red calipers)

I may do the same work when I start the repaint of my car

Edited May 15, 2006 by esprithk

[jfitz981]

Hey Jonathon,

Thanks a bunch for the reply...it does sound like something simple was missed. I will keep you guys up todate...it may be a few days before I have access to a lift to use. Thanks a bunch

J

[Jonathan]

Thanks Eric - what I publish it for to share info and to prove the car isn't as bad as it all seems to work on.

Jason you might find it just as easy to jack it up on the rear hoop and have a look underneath, sometimes when the car is lifted right up and clear from the ground the springs can push the suspension down too far and case issues when re-siting it...I had this occur when I done my back shocks for the 1st time, they often fall out of the correct location on the lower cup...you might have the colar of the damper actually catching the spring if this happens - as I say shout us some photos and might be able to spot the problem.

[islandbloke]

Or could it be the chassis/body bolt inside the boot space? On my car the whole body moves around the bolt - assume the GRP has fractured and I'll have to have it reglassed. My mechanic lifted the body at the rear wheelarch and showed me the movement - only slight, but enough to be adding to the cacophony of creaks and rattles!

[CarlC]

I think I know the sort of sound your talking about now. My car used to do this alot especially when I first got the car and wasnt used to the throttle. It took a couple of things to sort this problem out.

1- Engine Mountings needed replacing and had been bodged on one side by PO

2- I did a serious GRP repair with thin steel plates and GRP to rebuild the weak body to chassis mounting points in the boot. I have done a major write up for LEW including pictures if you want me to send it over to you to have a look at. The problem is just using GRP to repair this very weak area doesnt appear to be strong enough to keep it together for very long. But I suppose it depends how bad it is at present.

3- Possbily check the firewall between the cabin and the engine bay as there is some chipboard or similar that apparently compacts over time leaving a gap to the securing washers. You may want to do a forum search on this one for more info.

After doing #2 the car to body is solid to the chassis and there is no seperate movement. This was done last summer and its still perfect with no cracks or splits to date.

However from time to time after both 1 and 2 were sorted, I would still get a bit of a bump or bang but Im sure this was the engine cover. Im now very careful how I replace the engine cover and I have to say that I havent heard any sort of loud bang sine I've been doing this.

Edited May 18, 2006 by CarlC

[markt]

I've got exactly the same problem on my G-Car.

At idle, there is an incredibly annoying rattle.

Had a look-see last night and worryingly, I can physically lift the body by grabbing the wheel arch on the back right side (quite easily I might add) about 2 inches! WTF's going on here??? I can see the front left corner move down as I'm pulling up.

Sounds like exactly the same symptoms as Islandbloke's???

I spent quality time re-carpeting the boot and making things pretty two weekends ago and don't remember seeing great big bloody bolts holding anything together.

Don't know if the body mounts are in the same position as your cars, but could someone give me an idea or a piccy as where to look for the mounting points at the back of mine?

Thanks in advance - Mark

[jfitz981]

Hey Guys,

I just had a chance to stop by my mechanics to see what the deal is. I do not have any problems with the body mounts or anything like that.

It seems the wrong dampers were sent to me for the rear. The damper seems to be too long and when the ride height is adjusted to the height I like it ( only 1 inch lower than stock) the bottom seat is all the way at the bottom of the damper and it causes the damper to make the noise ...as soon as the ride height is lifted ....the noise is gone. Wierd but at least it seems that once I get the correct rear dampers (shorter ones) all will be fine.

Jason

[Jonathan]

Ughh thats why I ditched the AVO dampers I had, complete waste of space - the fronts (were the correct part #) didn't even fit !!! See my garage page.

Spent a while chatting to Brian Angus about it, they've seen a few differnet damper makes on cars there at the factory and been shocked at them and how they affect the car.

Hope you get that sorted, at least it's not the fronts which are an ARSE to change, unless like me you've had them on and off about 20 times

If you're not 100% happy hold out for the Lotus set that should be arrivng very soon - you can drop the car 10mm lower than standard with them but they are set up as per the factory.

[jfitz981]

By a chance...has anyone ever measured the closed length of their aftermarket rear damper?