Suspension Geometry Points

[indyzhp]

I'm just wondering if anyone knows of or has a catalog of BMW suspension points? I found various discussions on geometry programs, but WAY too many threads using the search term "suspension points" to go through. Or has anybody done a CAD model of a BMW suspension?

What I was mainly after was to look at the E36 M3 and E46 sedan. I'm just looking to see how a BMW's geometry behaves.

[Steve J.]

Are you plugging them into a program? How are you going to manipulate the pickup points to determine how it behaves?

What specific characteristics are you looking to define/determine?

[bmwretard]

What I was mainly after was to look at the E36 M3 and E46 sedan. I'm just looking to see how a BMW's geometry behaves.

[epj3]

My understanding on the stock suspension. Please, if you know better than I, post!

Front camber decreases as the suspension compresses.
Decrease in camber causes toe to go more negative

Rear camber is supposed to increase as it compresses.
Toe should not be greatly effected by suspension compression, but toe should go slightly less negative under acceleration.

[dak656]

I'm just wondering if anyone knows of or has a catalog of BMW suspension points? I found various discussions on geometry programs, but WAY too many threads using the search term "suspension points" to go through. Or has anybody done a CAD model of a BMW suspension?

What I was mainly after was to look at the E36 M3 and E46 sedan. I'm just looking to see how a BMW's geometry behaves.

I hear there is a lawsuit against Nascar right now, and Dixon is kicking ass in the IRL.

Just thought I'd throw out a couple more statements that don't answer your question.

[indyzhp]

I hear there is a lawsuit against Nascar right now, and Dixon is kicking ass in the IRL.

Just thought I'd throw out a couple more statements that don't answer your question.

ha, nice.

Everybody, I am not really after "tuning" anything, I just wanted the physical measurements of the suspension points on the body and at the wheels. Basically everything to put the points into any geometry program/CAD model/whatever just to see how BMW goes about suspension geometry.

[M-SWEET]

[indyzhp]

This started as a thread to see if anyone knows the physical geometry of BMW suspensions (ie XYZ coordinates). This can also serve to answer other peoples curiosities and add to the education of the forums, so let's not fill it with OT comments. I would think that anybody that seriously races their car would have this simple and fundamental piece of information. If you do have it and don't want to share, that is completely understandable. I'll probably get my car up on jackstands some weekend and just measure it myself if nobody knows.

[Steve J.]

What suspension program are you using?

[indyzhp]

It depends, I might use Mitchell, scheme it up in SolidWorks, write my own in Excel or Matlab or use a few others I have available to me.

[B.Watts]

My understanding on the stock suspension. Please, if you know better than I, post!

Front camber decreases as the suspension compresses.
Decrease in camber causes toe to go more negative

Umm, no...negative camber most definitely increases as the suspension compresses.

[MIMI1]

I have nothing constructive to add here but omfg

[Jlankes]

I was interested in doing this as well, and have the scanning equipment and kinematics package to handle the points, however the biggest problem is establishing bushing and link compliance. The rigid kinematics are somewhat straight forward, but adding in the compliances can wildly change the results - and verifying those results for integrity is far tougher.

[Steve J.]

Just use Solid mount geometry.

I have a couple spread sheets around too, it should be all you need to do a basic analysis of the geometry if that is all you're looking to do.

Is there one specific area you are trying to develop? Or are you just curious how the car works?

Also, are you using OEM points, or available packages that change the pickup point geometry? With Mitchel and Excel you could setup a range of points and geometries and track what geometry and dimensions come close to whatever your goals are.

I'm pretty sure I have E30 chassis specs somewhere, they are guidelines for making sure the e30 chassis is straight and aligned.

I don't think you need to do anything in solidworks really, unless you were designing components to work into it, it can be strictly through numbers in a program that uses basic algorithms and calculations to determine the geometry and movements in 3D.

[TXBDan]

Something more suspension oriented would probably be more useful than solidworks.

I used this: http://performancetrends.com/rc.htm for converting a 1st gen RX7 (has struts stock) to an SLA front end. Its only 2D so it won't help w/ castor, antidive, etc, but its a great learning tool. I used it w/ a few books, lots of references, to come up w/ a design for the car. The car hasn't been driven yet, so i can't say yet how well it works or doesnt but the model looks great and we actually managed to realize the model on the car.

[indyzhp]

I appreciate the suggestions on what software to use. I think it is somewhat of a moot point as that is not what I'm after. Typically when analyzing geometry, it helps to use a few programs as they all seem to have some quirk. SolidWorks is actually a pretty beneficial program to use. You can use the API teamed with Excel/VBA to create a pretty useful visualization of what everything is doing in 3D. And if you have the COSMOS Motion add-in, you can perform advanced movements.

And yes, I understand that there are compliant elements in the joints, etc. (which BMW has intentionally designed in there), but I'm just looking at the simplified rigid model. Anyway, I think the answer to my original post is a big fat no. So when I get a chance, I'll probably be measuring up my E46 sedan.

[JamesM3M5]

Sorry dude, the companies that have done the research aren't too keen on giving it away for free just yet. Gustave did some measurements on the E30 M3 back in the late 90s (e30m3performance.com), many years after the last E30 rolled off the lines. Since the E36 and E46 are incredibly similar, you probably won't see anything about them for a while. It's not that we don't love you guys, it's just that this stuff is hard work.

And it is useful to use a real suspension program, not just 3D modeling software. You want to KNOW what the geometry is doing by the numbers, not just see it. We use Susprog, since it does E36/E46 trailing arm/lateral link suspensions.

[Steve J.]

Yea, I'm a bit confused on what you are looking to 'see.'

You can just go out to the garage and remove the springs and move the suspension through the motions and see it in 3d

Why simulate something you have in 3d in your hands?

[dak656]

I appreciate the suggestions on what software to use. I think it is somewhat of a moot point as that is not what I'm after. Typically when analyzing geometry, it helps to use a few programs as they all seem to have some quirk. SolidWorks is actually a pretty beneficial program to use. You can use the API teamed with Excel/VBA to create a pretty useful visualization of what everything is doing in 3D. And if you have the COSMOS Motion add-in, you can perform advanced movements.

And yes, I understand that there are compliant elements in the joints, etc. (which BMW has intentionally designed in there), but I'm just looking at the simplified rigid model. Anyway, I think the answer to my original post is a big fat no. So when I get a chance, I'll probably be measuring up my E46 sedan.

I hear there is a lawsuit against Nascar right now, and Dixon is kicking ass in the IRL.

Just thought I'd throw out a couple more statements that don't answer your question.

I hear Obama is running for president.

[epj3]

Umm, no...negative camber most definitely increases as the suspension compresses.

Ah yes, Not sure why I thought otherwise when I posted. I should know better (since I know my minimum camber goes more negative when the car is lower )

[Dino Antonov]

You can just go out to the garage and remove the springs and move the suspension through the motions and see it in 3d

Thats what I ended up doing in order to determine whether I had picked up any bumpsteer when altering my ride height.

[Steve J.]

If you have a couple inexpensive measuring devices, and a free weekend, you can get some pretty good static data, and interpolate dynamic movements.

While I was at RRT we did a bunch of very simple stuff, and they have since done a lot more, and have had fantastic results. We even did stuff like testing the effects of hitting bump stops, etc.

[epj3]

If you have a couple inexpensive measuring devices, and a free weekend, you can get some pretty good static data, and interpolate dynamic movements.

While I was at RRT we did a bunch of very simple stuff, and they have since done a lot more, and have had fantastic results. We even did stuff like testing the effects of hitting bump stops, etc.

Yea I agree - it doesn't take much in the way of tools to measure suspension geometry... except it takes a lot of time.

[indyzhp]

I hear Obama is running for president.

I think everyone here must be a politician, because they are good at not directly answering questions.

[Paul Strefling]

Has anyone sourced these points in the past 8 months, or I am going to have to measure them myself?