Sway bars

[pmansson]

Has anybody come to any form of conclusion about the "best" swaybars to use?
Yes, I know it depends on the form of driving you do etc.
And rubber vs poly bushings for the mounting of sway bars etc...

BMW changed the front ones from 19mm to 23mm in 1974 and the green ones are 25mm.
Similar changes at the rear from 16 to 18mm (or even 20mm??) and the green ones are 20mm plus can be adjusted.

I guess the question really is; are the green ones noticeably stiffer than the 18 and 23mm BMW/Eibach sway bars? If they are, is this mostly due to the poly bushings ???

I have the green ones with poly on 2 cars and can´t complain. I have the 23 on other cars, but they have stock wheels and tyres whereas the ones with green sway bars have the 16" wheels with modern rubber. Hence hard to compare...

Happy New Year,
Peder

 

[Mike Goble]

A small change in diameter drastically affects the stiffness of a sway bar, as the equation uses diameter raised to the fourth power. Going from a 19mm to a 23mm bar of similar design results in roughly a 215% increase in stiffness. Swapping from a 23mm to a 25mm bar results in a 40% increase in stiffness.

 

[Ed G]

Not to mention alloy used and heat treatment techniques. That is to say- one manufacturers might perform differently from another's even if they have the same diameters. You might say I'm splitting hairs but I would estimate differences could easily exceed 10%.

 

[PaulinPa]

BMW designers must have thought they weren't even necessary for the rear in 74!At least on the coupes,seems E3's still had them(which bolt right in by the way).

 

[gwittman]

I don't know what size the original front sway bar on my 70 2800 CS was but I think it was too small. When I was on the track with a BMW club high speed driving school, it had a lot of roll. Before the last session one of the instructors came up to me and told me he had been watching me in the corners and it was leaning so much he was afraid I was going to roll over. He asked me to be careful this last session so we could go home with a clean record for the week end. A friend took a picture of my car in turn 6 of the old Riverside Raceway with excessive lean and the inside rear tire off the ground.

I ended up installing a Bavaria sway bar and that helped a lot without being to harsh on bumps. I think it was only a couple mm larger than my original but I don't remember what size it is.