Swaybar mounting location

[markseven]

Why is it better to mount the sway bar to the strut rather than the control arm? Are adjustable end links the only reason?

[Varinn]

I'm not 100% sure but I've heard that it also has to do with positioning. The control arm mount doesn't have the same direct correlation to suspension travel like the strut does and has more potential flex as well. Example would be that the strut could compress upwards by 4", but between the control arm mount point might only be 3" (made up numbers) due to flex and position. There was also something about as the struts are turned/rotated but I don't remember the details on it or what the effect was.

[TobyB]

Yeah, motion ratio is a good reason- the stock location (non-M)
is closer to 2:1. That means that for the same effect, you have to have
a 4- times- stiffer bar, which is a lot heavier and any compliance or slack is also multiplied.
Plus, I guess, it adds stress to the ball joints in the vertical direction.

The strut mount does move the bar when the wheels turn, but in theory, both
ends move a similar distance, so it cancels...

What I got,

t

[varg]

It's all about motion ratios. Since the strut tube mount is outboard relative to the control arm mounts, the swaybar must twist more for the same amount of independent suspension travel. Even though the ends of the swaybar don't change position laterally at all, they are directly attached to the strut tube and thus move the same distance as it does, the result is an increase in wheel rate for the same spring rate.

[markseven]

Varinn, Toby, varg, thank you for the info / insight. Makes sense!

[rwh11385]

This is one of the best bang-for-the-buck mods we've done, especially since E34 swaybar endlinks were $13/pair from FCPeuro and the tabs are $15 from AKG. But the results as far as reduced body roll and improved handling were noticeable.

[vpilarrt]

This is one of the best bang-for-the-buck mods we've done, especially since E34 swaybar endlinks were $13/pair from FCPeuro and the tabs are $15 from AKG. But the results as far as reduced body roll and improved handling were noticeable.

If the effective ratio is 2:1, as Toby says, this would mean the stock OEM bar (20mm) is effectively a 23.8mm bar. Did you notice an increase in understeer? Which springs and rear bar are you running?

[e30_302]

E30's (really all MacStrut cars) need a lot of front roll resistance to keep the camber curve in check. Conventional wisdom doesn't always apply to these cars.

[TobyB]

If the effective ratio is 2:1, as Toby says

I was guessing. The OE non-M mount is way inboard. But I didn't measure.

a lot of front roll resistance to keep the camber curve in check.

Agreed. It can be counterintuitive, sometimes. And it interacts with spring rate
a lot more than a real (racing) suspension does...

t

[markseven]

I wonder why BMW didn't use the strut mount on non-Ms... bean counters prolly got their way...

[Streichholzschächtelchen]

When pushed to the limit m3 e30s lift the inside front wheel, I'll be sticking with standard mounting position and eventually a 22mm sway. If insane stiffness is what you are after IE makes a hollow 25mm, addco makes a solid one incher.From what I've gathered both are overkill, and it seems that stanced cars are the ones binding at the links.

I crunched numbers and the ie hollow should be ~166% the stiffness of the 22mm most people use, the addco bar ~177% stiffness of the 22mm. This is if the materials used are apples to apples in terms of metal used.

[e30_302]

If you're lifting the inside front, you probably need more rear spring.

[straight6pwr]

When pushed to the limit m3 e30s lift the inside front wheel, I'll be sticking with standard mounting position and eventually a 22mm sway.

upgrading to a 22/23mm bar -or- moving the mounting tabs to the strut and leave the stock bar both accomplish the same thing. your comment suggests you think your way is better. for someone who can weld, or can get it done by a friend, moving the mounting tabs is a lot more $$ friendly. $30 versus $190+

[markseven]

upgrading to a 22/23mm bar -or- moving the mounting tabs to the strut and leave the stock bar both accomplish the same thing. your comment suggests you think your way is better. for someone who can weld, or can get it done by a friend, moving the mounting tabs is a lot more $$ friendly. $30 versus $190+

Maybe I am not reading your post correctly, but E30 M3s have the tabs on the strut tubes from the factory...

[straight6pwr]

Maybe I am not reading your post correctly, but E30 M3s have the tabs on the strut tubes from the factory...

my comment was about non-m3s.