Rear suspension topping out

[GHW]

I've recently picked up an ex-Academy Caterham which so far is absolutely brilliant.

However, I'm noticing some loud clonking from the rear end when going over not-particularly-huge road imperfections. It sounds like the noise happens when the wheel drops - like the suspension is "topping out" when the wheel droops.

I've jacked the back of the car up in the air and it looks like the axle tube is resting on the chassis when the suspension is at full droop. Is that normal? Could it be the source of my clonk?

[BertBert]

Doesn't sound right, certainly. Are there any witness marks on the chassis? I've not got a dedion 7 to check against though I'm afraid.

[framerateuk]

GHW said:

I've recently picked up an ex-Academy Caterham which so far is absolutely brilliant.

However, I'm noticing some loud clonking from the rear end when going over not-particularly-huge road imperfections. It sounds like the noise happens when the wheel drops - like the suspension is "topping out" when the wheel droops.

I've jacked the back of the car up in the air and it looks like the axle tube is resting on the chassis when the suspension is at full droop. Is that normal? Could it be the source of my clonk?

It's not the rear anti roll bar knocking about is it? Have a check of the droplinks - I had to change mine when I bought my car.

I know some people tend to disconnect the bar and cable tie it. Check that hasn't been done and is a bit loose.

[Drumster]

Jusr checked my '93 de dion with lower suspension mounts through the centre of the tube as it's on the ramp at the moment and the DD tube is circa 30mm above the chassis tubes when suspensionn is at full droop.

[GHW]

I had it up in the air again today. There’s no rear anti roll bar - Academy cars don’t have them. Looking down the chassis towards the axle tube, they’re definitely contacting:



There are clear witness marks on the passenger side, less so on the drivers side.

I also measured the ride height when it was on the ground and it was roughly 160mm, which doesn’t sound too far from normal.

I guess I should probably try to get hold of some C spanners and experiment to see if lowering will create some clearance..

[DanMalkin]

Have you changed dampers or the de-dion? Could be thst you’ve got the dampers for the below the de-dion tube but a sleeved/ central mounted shock de-dion tube

[BertBert]

Yes I was trying to get my head round it and the ride height is not a factor in the amount of droop available. That's determined entirely by the free length of the damper. So to solve it you need different dampers as you look to have the wrong ones. The poster above may well have the explanation for that.

ETA or have your current ones adjusted with different packers inside.

[Drumster]

Photo re my post above..

[Turn7]

Drumster - Powerflex bushes ?

How do you find them ? Ive some knocking from the rear I cant find and am thinking about the A frame with powerflex, and then the Suspension arms in the winter..

[Drumster]

Turn 7, there are no Powerflex bushes on my 7 just the basic metalastic ones all round including the A-frame.

If you're referring to the little bit of purple you can see that's the lower mount on the Quantum damper in front of the de dion

[Turn7]

Ah, didn’t think of that!!

cheers for the reply.