Knocking in rear suspension after changing to new struts

[PeteH]

Hi,

That's good news.

But can you explain how the spring is moving? It shouldn't be able to rotate as the bottom seat stops that, and there shouldn't be too much lateral movement as the top hat has a spigot to locate on the ID of the spring.

Thanks,

Pete

[Viper]

The 'spring' itself doesnt move, but as its compresses, the 'compressed' spring attempts to rotate around the shock in order to try and balalnce itself out.

As the bottom of the spring cannot rotate around, the top must do so.
Without the grease, the top binds with the rubber and makes a not so nice sound.
With the grease it acn be free to rotate around.

I think its in the order of like 1-2mm or something very small.

[Mr DOHC]

reppage for you

[PeteH]

Hi,

Ok so not being entirely convinced with the spring rotating during compression explanation, due to having owned/owning vehicles with coil rear setups and never having experienced this problem first hand, I spent some time yesterday afternoon with a tensile testing machine, some helical compression springs and a drop saw………the joys of being bored at work and not having to report to someone….

So what did I find??? Well in short I found that springs that sit neatly between the upper and lower seat, i.e. ends are ground and are parallel to the seats, do not display rotational or lateral movement when compressed. But springs that do not sit neatly, ie the top leg contacts the seat on an angle, tend to try and kick out or over when compressed.

Mr DOHC and Viper, I believe the cause of your problem is ill fitting springs, ie the top and/or bottom of the spring do not contact the spring seats properly and the result is the spring is trying to push out sideways when being compressed. The knocking sound is the spring moving relative to the upper seat until it is either stopped by the top hat spigot or it has found the "happy" point.

Grease may work for the short term but once lubrication is gone the noise will return. I'm sure the grease just allows the spring to slide instead of popping and grabbing. A possible solution would be to have the spring end ground so that it is closer to parallel were it contacts the spring seat…………….or maybe just get new springs with a better fit??

EDIT: I think I now know how the guy that reinvented the wheel feels

Cheers,

Pete

[Mr DOHC]

but mine are 5 year old springs that used to be ok?

[PeteH]

but mine are 5 year old springs that used to be ok?

Hi,

Well in that case I'd go simple and just be looking at whatever you swapped.....

Logic says that if it wasn't knocking before hand and began after changing something then whatever you swapped is making the noise.........and of course that everything is tight because I just scrolled down and re-read your posts and you haven't mentioned checking anything

Pete

[Mr DOHC]

i wonder if its the different rear seat/shock combo, might have to have alook

[PeteH]

Hi,

You do have to change the bottom seat if using an A70 strut and MX83 spring. The A70 spring has a larger ID so the MX83 spring will not seat properly.

Pete

[Viper]

Yeah, you have to knock off the old seats from the x83 shocks and wack em onto the A70's.

Maybe you swapped the rubbers left-> right and hence the spring now sits in a diff. location??

[Cuzzo]

So this is the problem im having at the moment, and is vipers old setup.

shocks arent fooked, so a greasing it a reseating it will get.

WTF!

[Viper]

Hey.. are they doing it again...
Fkn shit-o... :-/

If you can get a new set of the top mounts I'd go that way...
Maybe even make a steel spacer to sit ontop of the springs.
That was my next step