Suspension side-to-side shaking

[antonvh]

I have along post of my very frustrating problem an no one can put their finger on it. I received many speculative comments but nothing makes sense and I can't keep replacing parts until someone guesses right. I have a E30 318 cabriolet. I beleive the suspension is hard on these cars but it doesnt feel right. Whn I go over a slightly rough patch then the car shakes what feels like side to side from the nose to the rear. it is not a up or down movements and it is not comming through the steering. I have replaced control arm bushes, rear shock mounts and repaired the steering rack, all making some sort of difference but the side to side shacking is still there. I had the shocks and suspension checked out for a third time today and these guys say all is in order (shock are good). They only found that the new steering rack is already wearing on the left front shaft (up and down play) and say it must be the cause. I doubt it as the shaking I feel feels like the car is mounted on rubber balls and is moving side to side. Rubber mounts make sense but there is so many, I can't just keep replacing them.

Could it be a standard feeling in these cars?
Will strut bar across the engine help?

This is such a beautiful car, just whish I got get rid of this vibration

 

[328ii]

Silly question : what wheels and tyre / pressures are you using..?

Have you verified that the wheel alignment is right..?

I've seen guys using the wrong specs during wheel alignment which will make the car feel 'loose'

8?>

 

[Truvalu]

Wheel alignment could be a major influence...

Do you need to, and do they add weight to the car when doing the alignment?

 

[328ii]

Silly question : what wheels and tyre / pressures are you using..?

Have you verified that the wheel alignment is right..?

I've seen guys using the wrong specs during wheel alignment which will make the car feel 'loose'

8?>

More thoughts about the suspicious suspension movements

As your car has no roof supporting structure, it could be that the vehicle chassis
stiffness has diminished due to age and metal fatigue. If the suspension is hard,
vibrations/shocks are more absorbed by the chassis than by the suspension
causing the oscillations that you feel.

You can try with driving with low tyre pressure(s) and see if the situation improves...
Also try use higher profile tyres for softer sidewalls.

Only solution in such a case (i can think of) is either using a softer suspension
for improved dampening or strengthening the chassis - possibly fitting a more
solid roof structure to increase the chassis's stiffness...



8?>

 

[Jandre]

Cabriolet vehicles will have a bit more flex than a sedan. This is due to the loss of the roof. Although they strengthen the chassis to compensate, there still is a bit of flex.

This might not be the case on your car, but I would suggest taking another cabriolet for a drive and see if that car does something similar.

I have never driven a cabriolet, and could be talking absolute bollocks.

I too am finding my e34 drifting ever so slightly after I fitted 17" rims and wider tires.
Still need to figure that out.

 

[WyKiD]

I am not sure about the e30 cabriolets but on the E36 convertibles, you do get this sensation of a vibration running through the car when driving over a rough surface. The term for this is "scuttle shake" which is caused by the loss of body rigidity as a consequence of removing the roof. They do beef up the chassis but on earlier model convertibles it is more pronounced as when compared to E46 vert's and later models.