Suspension suspense

[Arde]

Been thinking about the next tweak to improve handling, already have fresh Bilsteins but my E24 has better handling with its really old Dinan setup.

I thought I needed fresh coils, yet when I asked the experts I hear coils do not age. Is that true? Back to basics, a spring produces a force proportional to the displacement from its rest position (within a range). Are we saying the constant k between distance and force does not change over time and use?

What is the equation for the shock? Is it just a force proportional to the derivative of the distance? Or does it have a distance component just like the spring? If so what is the ratio between the k of the spring vs. the k of the shock?

Finally, I am tempted to try just sway bars, as they produce their own force in parallel with the spring but I can increase that force without changing the geometry (unlike lowering springs). Do sway bars age? Is my stock sway bar wimpy? Who sells stronger sway bars than stock that bolt right in? Has anybody upgraded just sway bars and is happy with the result?

So many questions.

 

[deQuincey]

Been thinking about the next tweak to improve handling, already have fresh Bilsteins but my E24 has better handling with its really old Dinan setup.

I thought I needed fresh coils, yet when I asked the experts I hear coils do not age. Is that true? Back to basics, a spring produces a force proportional to the displacement from its rest position (within a range). Are we saying the constant k between distance and force does not change over time and use?

What is the equation for the shock? Is it just a force proportional to the derivative of the distance? Or does it have a distance component just like the spring? If so what is the ratio between the k of the spring vs. the k of the shock?

Finally, I am tempted to try just sway bars, as they produce their own force in parallel with the spring but I can increase that force without changing the geometry (unlike lowering springs). Do sway bars age? Is my stock sway bar wimpy? Who sells stronger sway bars than stock that bolt right in? Has anybody upgraded just sway bars and is happy with the result?

So many questions.

as usual i can not answer such complicated questions, but being an educated jesuit, I will add one burden to your sins, thus adding a variable to this equation, the rigidlty of the system is crucial to the result, handling a mechanical system like an automobile is affected by the torsional rigidity, and probably you can not change that variable too much without filling the interior of your lovely verona with odd and strambotic bars
ces't la vie !

lateral accelerations are very unhealthy, so drive slooooowly and you will solve two problems in one shot

 

[Arde]

as usual i can not answer such complicated questions, but being an educated jesuit, I will add one burden to your sins, thus adding a variable to this equation, the rigidlty of the system is crucial to the result, handling a mechanical system like an automobile is affected by the torsional rigidity, and probably you can not change that variable too much without filling the interior of your lovely verona with odd and strambotic bars
ces't la vie !

lateral accelerations are very unhealthy, so drive slooooowly and you will solve two problems in one shot

Yes, in roundabout ways I tried to obfuscate the sin behind my E9 handling anxiety until a savvy Jesuit monk saw through my deceit. Not long ago, in a land blessed by the sun, I merrily cruised at a healthy speed on an empty highway. I had to double check my destination address on the handheld GPS so I took my eyes off the road for a brief moment.

Jesuit or otherwise every blessing comes with a curse, and this land blessed by the sun is cursed by earthquakes. Bridges are being reinforced for such eventuality and when I lifted my gaze I was about to hit the temporary wall erected to protect the bridge reinforcement construction. Adrenaline and a sharp steering to the right saved the day, plus the adjacent lane being empty. The car stayed the course but the body roll was closer to what expect from a rental car though, and that is what I am trying to fix.

Assuming my sins will only increase with age I am looking at ways to minimize the punishment, not at pursuing sainthood.

Ok, can I have now the sway bar equation?

 

[Nicad]

In my experience (Non E9) making sure bushings are "as new" makes the biggest difference. That and fresh shocks and tires.

 

[kasbatts]

Get the Carl Nelson uprated sway bars
And a nice set of sport Bilsteins and you will have a nice set up with out compromising the current comfortable ride, although the sport shocks will firm up the ride a bit.
The sway bars will help with the body roll you have experienced and in turn the sports shocks will help to control the rebound of the up rated sway bars

 

[deQuincey]

Yes, in roundabout ways I tried to obfuscate the sin behind my E9 handling anxiety until a savvy Jesuit monk saw through my deceit. Not long ago, in a land blessed by the sun, I merrily cruised at a healthy speed on an empty highway. I had to double check my destination address on the handheld GPS so I took my eyes off the road for a brief moment.

Jesuit or otherwise every blessing comes with a curse, and this land blessed by the sun is cursed by earthquakes. Bridges are being reinforced for such eventuality and when I lifted my gaze I was about to hit the temporary wall erected to protect the bridge reinforcement construction. Adrenaline and a sharp steering to the right saved the day, plus the adjacent lane being empty. The car stayed the course but the body roll was closer to what expect from a rental car though, and that is what I am trying to fix.

Assuming my sins will only increase with age I am looking at ways to minimize the punishment, not at pursuing sainthood.

Ok, can I have now the sway bar equation?

beautiful text !
if only every request in the forum had a similar explanation this would become the best forum in the world !
my personal taste would have included a curse in the last phrase just to emphasize it, but anyway it is brilliant !

 

[Arde]

Get the Carl Nelson uprated sway bars
And a nice set of sport Bilsteins and you will have a nice set up with out compromising the current comfortable ride, although the sport shocks will firm up the ride a bit.
The sway bars will help with the body roll you have experienced and in turn the sports shocks will help to control the rebound of the up rated sway bars

OK, I will try sway bars with the current HD Bilsteins.
Are sway bars spec'ed by thickness or by force? If Carl only has one model it does not matter.

I should probably document the roll before and after in a video or something, otherwise I will never know it it was the placebo effect.

 

[Nicad]

OK, I will try sway bars with the current HD Bilsteins.
Are sway bars spec'ed by thickness or by force? If Carl only has one model it does not matter.

I should probably document the roll before and after in a video or something, otherwise I will never know it it was the placebo effect.

I look forward to your observations

 

[deQuincey]

OK, I will try sway bars with the current HD Bilsteins.
Are sway bars spec'ed by thickness or by force? If Carl only has one model it does not matter.

I should probably document the roll before and after in a video or something, otherwise I will never know it it was the placebo effect.

interested
you are right about the difficulty of the perception
but how are you going to document the roll ?
probably a setup of a fixed mounted camera and a pendulus inside the car and try to measure the angle before and after while passing the same bends at the same speed ?
because i assume that you do not have accelerometers ...you never know what do we hide in our garages !

 

[kasbatts]

Speced by thickness normally in millimeters, I'm not sure if he (Carl Nelson) has more than 1 sway bar sets, my guess is not.

I copied the below in from Suspension Techniques web site, says it all really..

--------------

ANTI-SWAYBARS
When tuning your vehicles suspension, there are many ways to change your vehicles handling characteristics. Springs, Dampers and alignment all play huge parts in affecting how your vehicle handles, but no component has as drastic effect on your body roll as the Anti-Swaybars without adversely affecting your ride quality.

To the average enthusiast, the installation of a ST Anti-Swaybar or Suspension Techniques Anti-Swaybar Complete Kit will result in a drastic reduction in the boat-like feel that many vehicles have with the factory or even mildly tuned suspension. By increasing the rate of the front, rear or both bars over the factory units, the ST Anti-Swaybars, your body roll will be reduced giving you more confidence on long sweeping corners, on and off ramps, as well as in emergency maneuvers.

For the Advanced Suspension Tuner, many ST Anti-Swaybars are built with additional adjustability either in the bar itself with multiple end link mounting points, or adjustable heim joint end links to tune in or out any undesirable handling characteristics of your current suspension setup such as over-steer or under-steer.

ST Anti-Swaybars available for the front and rear separately or in complete vehicle kits for a large range of vehicles. Each ST Anti-Swaybar is designed and produced in-house at our California facility and are constructed from high quality steel for precision performance, and powder coated for durability. All necessary high grade mounting hardware and bushings, as well as full instructions are included in each and every kit for simple installation.

------------------

As for measuring the affects before and after, I have seen in a suspenion book I have ("How to make your car handle" I think its called) using a video/fixed camera on a tripod, (same set up height, position etc, car at the same speed through the corner every time etc ( car going as fast as possible I assume to get the greatest body roll ) you need to find a corner close to home that you can whizz through a few times filming/photographing what the car does before and after, if you can get still photos and print them out, you can draw lines ( the ground and cars imaginary floor) get a protractor and measure the before and after angles, it's a bit hit and miss though I expect, the trick will be to keep all the variables as close as possible

 

[deQuincey]

hi kasbatts, in the suspension techniques, product finder i can not find the correct anti-sway bars set for our e9s

do you know if the set for the e28 and e24 will fit in the e9 ?

 

[Arde]

interested
you are right about the difficulty of the perception
but how are you going to document the roll ?
probably a setup of a fixed mounted camera and a pendulus inside the car and try to measure the angle before and after while passing the same bends at the same speed ?
because i assume that you do not have accelerometers ...you never know what do we hide in our garages !

I was thinking going around cones at a fixed speed at an empty parking lot.
The angle measurement is the crux, let's sort the options:

- A relative films the car form outside.
- Use a jar with coconut oil and see the marks on the inside of the jar.
- The iphone has an accelerometer, need to find the right app, using app search engine www.quixey.com and searching "measure acceleration on iphone" yields interesting results, like gcar for example...

Need to order the sway bars before I get into that. Why don't cars come with thicker sway bars?

One of the above is a shameless plug.

 

[kasbatts]

I don't believe e28 e24 bars fit, different width across the front apparently, and will rub on the chassis rails

As for our cars not being on the Suspention Techniques web site???, I read somewhere on the forum that the Carl Nelson bars are the same as suspension Techniques bars, maybe ST make them exclusively for Carl Nelson?? Anyone know?

 

[DaveG]

Why this hangup with body roll? Handling is about GRIP! Put the best tire you can on the car. It will help the handling more then all the other things combined....
DaveG

 

[inovermyhead]

Suspension suspence

Having fitted Carl Nelsons sway bar kit yesterday I thought I would share my thoughts and comments with everyone.
I have been doing a 3.5 transplant with a 5 speed conversion and took the opportunity to replace the anti roll bars having previously replaced the shocks and lowered and stiffened the springs( bilstiens sports, springs uprated by 20% and lowered 40mm front and back).
The Back:
Having fitted then removed the Anti Roll Bar(ARB) after seeing that handbrake cable needed to sit underneath the bar, we discovered that the ARB sat inboard of the vertical link by a good 25/30 mm. a call to La Jolla was required and Chris said slacken of the vertical link to allow the supplied bolt to be used, no said my mechanic, what's the point of having a fair amount of movement there??
Solution - use a 75mm bolt and fabricate a piece of steel tubing to act as a spacer and take up the 25mm or so that the ARB was out. Next problem the rear of the ARB once bolted up sat only 5mm or so away from the rubber boots of the rear axle, much to close to allow for any movement and destroyed rubber boot. Solution unbolt it all again and use both 5 mm spacers supplied on the vertical links to allow ARB to sit lower and away from the axle.

The Front:
First having tried to fit the steel bracket in to the slot in the chassis rail, no go. you have to bend the slot forwards to allow the bracket clearance which the means the bracket is tilted forwards ( up at the back where the bolt goes through the hole in the chassis rail) after much hassle got the bolt to go though only to find that there is no way to tighten up the lock nut from underneath because the original was not a conventional nut but an Allen key nut set in the recessed hole which made getting a socket on it impossible , solution - replace supplied nut with original Allen key one, but that is much shorter and as the back of the bracket is not sitting flat became a exercise in trying to compress the bracket down whist trying to put bolt up and trough,two of us with a crow bar and various other implements finally succeeded.

Be warned my experience working with an experienced race car engineer who has built at least two of these coupes for historic racing leads me to say these kits are not Plug and Play and would be impossible to do without having the car on a hoist.

Sorry for the rant but this took most of my day up yesterday for what seemed to be a simple job.

 

[snj5]

Ordered a set of HD Bilsteins and the Korman sway bar set with the adjustable rears. Any experience with the Korman kit, or rear bar settings?
Also going to CK staggered 16s with DSWs 205/55 and 225/50.
Thanks.

 

[kasbatts]

Why this hangup with body roll? Handling is about GRIP! Put the best tire you can on the car. It will help the handling more then all the other things combined....
DaveG

Yep, your right Dave, but, the more grip the faster you go around corners, the more body roll you get, it's a big vicious circle.
You need to keep the car as level as possible for good handling and passenger comfort if you like to drive a bit quicker than the norm, and the best way to do this is with anti roll bars (sway bars)

 

[G]

Looks like Ireland Engineering sells larger sway bars as well.

http://www.iemotorsport.com/bmw/E9-E3-suspension-steering/e9swaybars.html

 

[snj5]

It is interesting to see the differences:

Ireland: f/r 28.5mm/22mm
Korman: f/r 22mm/19mm

Is there such a thing a different bar materials? The diameter difference between the front bars above seem rather large.

 

[rsporsche]

bigger isn't always better. what you need is balance. the korman clubsport suspension i had on my 2002 was awesome. perfect balance at significant speed. if you are driving at full race speeds, then perhaps bigger might be better. too big of a bar can create an unbalance that can make driving less pleasurable. my previous e30 m3 was perfect with the stock bar - a thicker front bar made it much trickier to drive.

if you are going to drive primarily on a track - look for a tested setup for track speeds / conditions. if you are buying for road use - buy a tested setup for road conditions. tested is the operative word. i know that korman has tested for different uses. ireland makes good products - but i do not believe they have created a tested package.

if you want to experiment - buy pieces and keep swapping them out and go driving and test for the best configuration. it sounds like an expensive route to me.