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[geoffr70]

Replaced my drop links with lemforders from Allgermanparts two nights ago at work (better than the pattern parts that were on). Also polybushed the ARB while I was on.

Anyway, there was a clear dull knock from the d/l when going over bumps, which has obviously now gone. My q is, where does this knock come from. I mean, yeah the ball joints on the old d/l had alot more play in them than the new ones, but by the nature of what they are and how they're fitted, I don't get where the knocking comes from. Does it knock against itself?

While I'm on, how the hell is the ARB meant to work anyway? Obviously once both d/l were off the things just a loose bar. Does it somehow transfer movement/compression to the other side to smooth it out and make it more comfy?

Can't see polybushed ARB bushes making a difference TBH, apart from longer life?

[TheBoy]

The d/l balls in the d/l sockets

[feeutfo]

Roll bars. It's purely the torsional twisting action of the metal bar that's important. The bigger the diameter and tortional strength of the bar the less the car rolls. When cornering the outside shock compresses so the roll bar rises with it in relation to the chassis, as it must, via the drop link. This puls the inside drop link and hence the shock up as well. And the opposite as true in that the inside shock extends that pushes the outside shock up... If that makes sense. So basically the two shocks are linked by the roll bar to keep the car level.
 The knock comes from the play in the drop link ball joint, but only when the roll passes through the level position and the twist on the roll bar transfers to opposite way, at that point there is no twist on the bar, so no force going through the ball joint to take up the play, so it knocks. In all other positions the twist on the roll bar means the play in the ball joint is taken up, so it can't knock.

This means they usually only knock when the car rolls from one side, through the level position where it knocks, to the other. Or most noticeably, when the car is rolling along quite happily on a flat plane and minor road bumps that are independent to one side move the wheel>shock>drop link up and down, so it knocks.

Or more simply, hold the threads of the ball joint one in each hand, and pull them away from each other then towards each other while holding them parallel to each other. If there enough play you'll be effectively feeling that exact knock signified by the play you feel in your hands. It's louder on the car due to the resonance of the metal parts on the car. The roll bar is effectively a bloody great spring, except it twists, rather than extends. Tap a spring and it will amplify the noise. Roll bar is similar but the bushes damp some of it out. That's their job.


...well that's my understanding anyway. Hth.

[feeutfo]

Re arb bushes, the firmer they are the better for the purpose of anti roll due to the average position between the ends the bar will want to tilt if it's not bolted to the chassis. Keep it flat via the bush clamps, and the levelling affect is vastly improved.

[feeutfo]

This shows how adjustable anti roll bars work
http://www.youtube.com/watch?v=3pgcN4XXqPU&feature=youtube_gdata_player
The twist he applies to the horizontal bar is immitating the movement of the suspension on the other side of the front axle.

[feeutfo]

This ones better, with graphics.

http://www.youtube.com/watch?v=9xr7ktz1_as&feature=youtube_gdata_player

[geoffr70]

Ah, all makes sense now, thanks CG

[feeutfo]

That's a relief then, confused meself there for a minute.

[jaykay]

Roll bars. It's purely the torsional twisting action of the metal bar that's important. The bigger the diameter and tortional strength of the bar the less the car rolls. When cornering the outside shock compresses so the roll bar rises with it in relation to the chassis, as it must, via the drop link. This puls the inside drop link and hence the shock up as well. And the opposite as true in that the inside shock extends that pushes the outside shock up... If that makes sense. So basically the two shocks are linked by the roll bar to keep the car level.
 The knock comes from the play in the drop link ball joint, but only when the roll passes through the level position and the twist on the roll bar transfers to opposite way, at that point there is no twist on the bar, so no force going through the ball joint to take up the play, so it knocks. In all other positions the twist on the roll bar means the play in the ball joint is taken up, so it can't knock.

This means they usually only knock when the car rolls from one side, through the level position where it knocks, to the other. Or most noticeably, when the car is rolling along quite happily on a flat plane and minor road bumps that are independent to one side move the wheel>shock>drop link up and down, so it knocks.

Or more simply, hold the threads of the ball joint one in each hand, and pull them away from each other then towards each other while holding them parallel to each other. If there enough play you'll be effectively feeling that exact knock signified by the play you feel in your hands. It's louder on the car due to the resonance of the metal parts on the car. The roll bar is effectively a bloody great spring, except it twists, rather than extends. Tap a spring and it will amplify the noise. Roll bar is similar but the bushes damp some of it out. That's their job.


...well that's my understanding anyway. Hth.

Many thanks for this info.  I was wondering what the noise was and this explained it perfectly.  New droplinks now fitted and noise problem solved!!

John