Rear Suspension Knocking - FINALLY SOLVED!!!!

[revilla]

Now I've got the car out for the summer, time to sort out a few little niggles ...

 

On rough road surfaces I'm getting quite a load "clonk" from the rear right suspension. It happens when either the front left or rear right wheel runs over a pothole. I'm usually alone in the car so there is more weight on that rear corner, but there is no similar noise from the left.

 

To describe the sound, if you imagine if you had a metal tool box in the boot with one hefty metal tool in it which bounced and clonked as the back end bounced over a bump, that's about it! From the driving seat, the sound almost sounds like it comes through the roll bar, but I've checked the roll bar is secure and I think it is more probably just "ringing" through the roll bar from the damper attachment just below it. I've tried emptying the boot to make sure it isn't anything in there rattling too.

 

It doesn't rattle continually, just the occasional load clonk on bigger bumps.

 

I can't see anything loose or any witness marks of anything making contact. All nuts and bolts seem secure.

 

Anyone got any ideas?

 

Any suggestions gratefully appreciated.

 

Edited by - revilla on 5 May 2013 12:38:21

 

Edited by - revilla on 12 Jun 2013 10:24:36

 

Edited by - revilla on 12 Jun 2013 21:42:28

[Garth]

What car and diff have you got?

[Wrightpayne]

Do a search on dedion failures so you know which bits to check as routine.

 

My money is on the top of the shock hitting the thin headed bolt that screws into the under side of the roll bar. Possibly the bush needs changing in the shock.(assuming you have an FIA bar)

 

The dedion tube runs pretty close to the back of the diff - just check for any missing powder coat / bright spots.

 

You joining the run to Stoneleigh?

 

Ian

 

 

Edited by - Wrightpayne on 2 May 2013 21:13:28

[Stationary M25 Traveller]

Is it the deDion tube hitting the chassis at the ends ?

 

Do you have a Watts linkage with the two little rod end bearings that connect to the deDion brackets ?

 

These get rattly and need replacing regularly. Remove the wheel and grab hold of each arm and try and shake it violently. If you need any ..... my pal is a bearing supplier and offers good prices.

[Mabbs]

Possibly too simple but I had a similar noise and it was the nut on the spare wheel slightly loose. Worth a look if you have one.

[revilla]

Sorry I should have said, 2003 Roadsport SV VVC Imperial De Dion.

 

I don't have an FIA bar, just the standard bar. Looking at the top damper mounting I can see a bolt hole above it which I guess must be where the FIA bar mounts, but there is no bolt there to hit and there is no sign of any rubbing or excess movement.

 

I do have the Watts linkage but again everything seems tight and secure with no play.

 

No sign of the De Dion tube catching the chassis. I can't see any sign of it catching the diff but I'll take a better look later.

 

The spare wheel is secure.

 

Of all the suggestions the top of the shock knocking a bolt head sounded the best fit. Could a fault damper actually be noisy?

[Stationary M25 Traveller]

How many miles on the car ?

[revilla]

Just under 14k... What are you thinking?

[Stationary M25 Traveller]

I'm thinking it is hardly run in. Mine is a 2002 SV with 61k.

[TomB]

Ive just had this and investigated it to be the rear anti roll bar (over the diff type).

 

The cotton reel bushes seemed to be a touch loose and allowed the bar to rattle around in the mountings. I stripped and put some silicon lube spray and it stopped. Ill replace the bushes in due course - I could replicate the noise when static by rocking the car side to side with the roll over bar before I did this.

[Stationary M25 Traveller]

Lift the rear and remove the wheel before trying to shake the rod end bearings.

 

Do you have adjustable platforms on the suspension ? If too high at the rear, DD may sit fown on chasdis tubes. Grab hold of top of sideskin in boot and lift/push down car by hand to see if it clonks.

[sjmmarsh]

TomB

 

I was just about to suggest the ARB. Tie wrap some foam round the bar where it goes over the diff - it made my knock go completely.

 

Steve

[David Lynch]

Also look at the handbrake cable routing. Must check my Anti Roll Bar, good call that

[revilla]

My car was flat-floored by Fishy Dave, it does have adjustable platforms at the rear but we couldn't actually get it as high as we wanted because I would need to get more grooves machined on the body of the shock for the circlip, so if anything it's riding a bit low front and rear to get some rake, but nothing out of the ordinary.

 

No amount of pushing, shoving, lifting or throwing my weight onto either the rear of the boot or the roll bar produces any unusual noises at all.

 

As for the ARB - do they all have one at the rear? I couldn't see one fitted on mine, although I did only have a quick look before work this morning, but I would have expected it to be fairly obvious?

 

It was still doing it on the way to work this morning, 30 miles of smooth roads and nothing then through a little village with rough roads and clonk! It's really odd, from the driver's seat it really does sound like something metallic hitting the roll bar, like somebody dinging the roll bar with a spanner, the sound seems to be coming from too high up to be De Dion related, like right from the top of the shock. There's no sign of any movement around the roll bar mounts and everything seems secure. The boot was empty and I've even taped up the the Y-pieces where the SBFS half hood attached at the rear to make sure the buckles weren't slapping on the plastic cover over the fuel filler downpipe.

 

I'll get it jacked up on Sunday and get underneath to see if I can spot any witness marks anywhere, but for now I'm still completely at a loss.

[Stationary M25 Traveller]

As above ... handbrake cable can slap bulkhead behind your seat pretty heavily !

[revilla]

David Lynch and SM25T I will have a good look at the cable routing over the weekend, it does sound like distinct possibility thanks.

[tangomikeromeo]

Drop link arms? They had failed on my similar vintage, VVC SV (if it's relevant), and resulted in loud clonking over bumps.

 

As per previous posters ARB waggling most likely to reveal.

[revilla]

OK I've found the source of my knocking but I still don't understand why it's happening. The inner top edge of the spring is fouling the metal panel behind it. The lip on the top edge of the spring here is polished and there is a clear evidence of it fouling the metal panel behind here. I've checked all the other possible culprits while I had it in bits, the handbrake cable is secured with ties against all of the components it could slap against and there is no real scope for movement. I don't have a rear anti-roll bar, so it's not that or the drop links, and the de Dion tube seems to clear the chassis throughout the suspension travel and is well clear of the diff casing, so it looks like this is the only cuplrit.

 

The thing is, all of the bushes look good, the top shock bolt was secure and by fitting it with the shock removed I can see it passes right through the shock and firmly into the captive nut (i.e. the correct length bolt is fitted). Nothing looks generally out of alignment and the car handles fine, so why is the spring fouling like this?

 

The spring does "stick out" quite a bit wider than the carrier, so it is possible I have the wrong springs fitted?

 

Any ideas please?

 

 

[revilla]

OK a bit more info, I've had a look at the other side to compare and it's fouling on BOTH sides, although the problem is worse on the driver's side. This corresponds with what I've been hearing, mostly clonking on my side but generally a bit noise suspension. Picture of passenger side here.

 

Given that it is happening on both sides, I doubt its down to something being bent or out of line. As it is right at the top of the spring, it would take an awful lot of lateral movement of the de Dion tube to move the top of the spring enough to do that. I can't see any other sign of excessive movement of the whole suspension laterally. So, is it ..

 

i) A design fault? I which case why aren't other people complaining, or are they?

ii) Wrong parts fitted?

iii) Right parts but wrongly fitted?

 

I'm stumped. Any more suggestions please?

[revilla]

The springs are marked as Caterham 71198 which seems correct here.

 

Edited by - revilla on 5 May 2013 12:36:51

[NoLimits]

Your dampers have been installed upside down.

 

Turn them over so the body of the unit which is narrower is at the top.

 

[revilla]

Really? When searching for the part number 71198 I found this which states "Rear dampers must be fitted with the main body fixed to the De Dion tube (right way up)." and the only photographs I could find on the web look like this which is the same way up as mine.

 

I've got adjustable platforms. Turning them the other way up would put the adjustable platforms in the tunnel, meaning that the WIDER parts would be there, not the narrower end.

 

In addition if I try turning them the other way up, the cone shaped end shown in the photograph fouls the do Dion tube long before the bush is clamped up against the mount, so there would have to be some sort of spacer collar missing.

 

I'm confused

[NoLimits]

Its a long time since I had standard dampers on the car so I may well be wrong.

 

However I always had some washers between the bush and the tube on the bottom in order to provide clearance.

 

I'll try and look through some old pics of my original build.

 

You have me thinking now

 

[revilla]

I know what you mean, there is one washer in at the moment - the problem is that putting more washers between the shock lower bush and the mount on the de Dion tube would move the shocks FORWARD, but as far as I can see to stop them catching they need moving OUTWARD as it is the inner edges that are catching, not the front or back. I think the pictures I posted show where the contact is occurring. It really doesn't make much sense to me at all, it's like a basic design problem but I can't find any other references to anyone else with the same problem so it can't be.

[SLR No.77]

Is it possible that the small turret panels have been pushed in from the boot side at some time on the past causing them to foul? The simple answer might be to carefully reshape the turrets to give a little more clearance.

 

Stu.