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Old 04-13-2009, 10:11 AM   #1
mateospeed
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Default Has anyone measured or plotted suspension geometry?

I'm starting to dig very deeply into the problems with the front suspension on the WRX. (I have an '02.) To do this, I've realized that I really do need to plot the geometry and motion of the suspension, most importantly the front end.

Has anyone measured the suspension before? More specifically, the length and placement of the actual arms/links, the uprights, and the struts? Also, the location of the pickup points on the car? If someone else has managed to accurately measure these points, it would certainly save me from doing that work over again.

From there, i plan to make a quick model of the suspension and investigate potential changes to make the suspension move "correctly" at lower ride heights; those more appopriate to a track/ road race car.

Oh, some background on me: 2 things that are important.
1) I'm a mechanical engineer for the Marine Corps in Cherry Point, NC.
2) I campaign a Spec Miata racecar in SCCA.
3) I'm also a driver coach and instructor for most clubs (so at least I'm not a complete idiot:-))

So, if anyone has started to do this, I'd be extremely interested in talking to you/ anyone else who's interested, and we could actually do something useful instead of throwing lots of "band-aid" parts at the car, correcting little problems with the suspension.

Thanks!
-Matt McBride
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Old 04-13-2009, 10:22 AM   #2
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there is a thread in the GD chassis suspension forum on IWSTI. I've been meaning to. Maybe i will set aside this weekend to do so, now that it's warm out.

I will be simultaneously measuring '07 wagon annd '04 STi components.

EDIT: assuming this predicted rain doesn't happen. :-/


EDIT again: maybe i'll just do it tomorrow.
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Old 04-13-2009, 11:59 AM   #3
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Sniper1rfa, I would really appreciate the data on the '07 wagon if you don't mind. You use solid works yes ?
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Old 04-13-2009, 12:25 PM   #4
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Quote:
Originally Posted by sniper1rfa View Post
EDIT again: maybe i'll just do it tomorrow.
That's what I'm talkin' about!

Quote:
Originally Posted by sniper1rfa View Post
there is a thread in the GD chassis suspension forum on IWSTI.
Any chance you could point me a link? I'm very interested indeed!

EDIT:
1)
Quote:
Originally Posted by UFOpilot
You use solid works yes ?
If that was directed t/w me, yes, I used to use solidworks. My new company works with Microstation, unfortunately, so I'm re-learning everything.
2) Sniper, What system of measurement are you using? I haven't been able to come up with anything that's accurate enough for me to trust.
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Old 04-13-2009, 12:45 PM   #5
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Metric. Given the amount of slop in all the mounting points (as well as all the available adjustments) i plan to just use a metric tape measure to the nearest millimeter. That should be plenty accurate to get a good feel for any suspension changes you wish to do.

I will have a solidworks file done, and from that intend to also list just dimensions so people can use what i have.


Also, i should note that i will be using the spherical top mounts i have for the strut top mounting point. I can adjust for stockers, though.

http://www.iwsti.com/forums/gd-suspe...ion-model.html
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Old 04-13-2009, 12:55 PM   #6
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Quote:
Originally Posted by sniper1rfa View Post
Metric. Given the amount of slop in all the mounting points (as well as all the available adjustments) i plan to just use a metric tape measure to the nearest millimeter. That should be plenty accurate to get a good feel for any suspension changes you wish to do.
I meant how you were actually measuring it: are you finding a centerline on the vehicle, then measuing outward from those points, etc?


Quote:
Originally Posted by sniper1rfa View Post
Also, i should note that i will be using the spherical top mounts i have for the strut top mounting point. I can adjust for stockers, though.

I have spherical mounts too. Don't worry about it.
-Matt
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Old 04-13-2009, 01:07 PM   #7
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No, i was going to point-to-point, under the assumption that the strut towers and subframes are reasonably symmetric.
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Old 04-13-2009, 01:09 PM   #8
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Roger. Are you measuring along some accepted axis?
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Old 04-13-2009, 06:15 PM   #9
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This has all been done before. What exactly are you after? What are your end goals?

Tony
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Old 04-13-2009, 06:21 PM   #10
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Me? Frankly, i'm just playing.


edit: Plus, having a model i can mess about with in solidworks would be interesting and helpful in learning about suspensions and general gadgetry.

Last edited by sniper1rfa; 04-13-2009 at 06:26 PM.
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Old 04-14-2009, 08:59 AM   #11
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Quote:
Originally Posted by Turn in Concepts View Post
This has all been done before. What exactly are you after? What are your end goals?

Tony
Suspension geometry re-design and fabrication. Don't tell me it can't be done; everything can be done, it just gets harder.

I first want to find out what I'm looking at (stock), and understand the exact reasons behind why the stock suspension sucks so badly.

When you say it's all been done before, what exactly do you mean? Have you done it, and what were your goals?

Thanks!
-Matt
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Old 04-14-2009, 02:56 PM   #12
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my 09 front



if you have software I'd love to see it modeled in that, little tough working w/ graph paper it did force me to re-learn some math I had long forgotten however
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Old 04-20-2009, 07:46 AM   #13
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Turn-in Concepts? Any help?
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Old 04-20-2009, 07:47 AM   #14
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Quote:
Originally Posted by sniper1rfa View Post
Me? Frankly, i'm just playing.


edit: Plus, having a model i can mess about with in solidworks would be interesting and helpful in learning about suspensions and general gadgetry.
Sniper, did you ever get around to taking some measurements?
-Matt
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Old 04-20-2009, 01:03 PM   #15
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No, i fell asleep in a chair outside on the lawn that day.
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Old 04-20-2009, 01:10 PM   #16
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happens to the best of us.
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Old 04-20-2009, 01:39 PM   #17
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subscribed
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Old 04-20-2009, 05:03 PM   #18
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Quote:
Originally Posted by mateospeed View Post
Suspension geometry re-design and fabrication. Don't tell me it can't be done; everything can be done, it just gets harder.

I first want to find out what I'm looking at (stock), and understand the exact reasons behind why the stock suspension sucks so badly.

When you say it's all been done before, what exactly do you mean? Have you done it, and what were your goals?

Thanks!
-Matt
ehh? It has been done before in that people on this board have modeled it with suspension modeling software. We have done our own work as well. It was all done in order to understand the best configuration for the suspension in terms of performance.

Tony
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Old 04-21-2009, 08:06 AM   #19
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And, as it typical, no one's willing to share that information. I don't expect a vendor to share, because they put in the work and are selling the products, but someone out there who did it just out of curiosity should be willing to share......?
Anyone???
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Old 04-21-2009, 08:38 AM   #20
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I've only seen it in a two threads - there was one by stretch on IWSTI, and this pdf posted by zzyzx:

http://forums.nasioc.com/forums/show...ht=roll+center

I don't think I've seen anything around here with just a list of measurements and the raw data for anyone to model their own - other than BIGSKY's graph.
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Old 04-21-2009, 09:02 AM   #21
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That is some great help, and fascinating information. The effects of inclining the struts inward are suprising; you'd think a more-inclined strut would cause a camber gain under bump, but it doesn't appear to...

Does anyone else have numbers on mounting point locations??
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Old 04-21-2009, 09:48 AM   #22
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if you want them, your probably going to have to get them yourself- I did

I simply jacked the car up and put them on stacks of 2x8's (f&r)- took measurements (actually tried to measure all points 3-4 times to insure they were accurate/repeatable)- then simply subtracted the height of the 2x8's out.

didn't take too long

obviously a level floor is a must
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Old 04-21-2009, 10:04 AM   #23
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Yeah, I'd certainly like to, but have 2 restrictions:
1) no level surface
2) no sure-fire way to measure those points very accurately.

-Matt
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Old 04-21-2009, 10:23 AM   #24
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Quote:
Originally Posted by mateospeed View Post
Yeah, I'd certainly like to, but have 2 restrictions:
1) no level surface
2) no sure-fire way to measure those points very accurately.

-Matt
I think those are the same restrictions that a lot of us have - that and time. I believe some of the suspension modeling software packages out there may have the data preloaded. But those are $$.

Out of curiosity - when you say "changes to make the suspension move correctly at lower ride heights", are you talking about modifying control arms and chassis mount points? There are a couple products out that allow you to drop the car a good bit and yet retain reasonable roll center heights without affecting bumpsteer.
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Old 04-21-2009, 10:26 AM   #25
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Quote:
Originally Posted by Mind View Post
I think those are the same restrictions that a lot of us have - that and time. I believe some of the suspension modeling software packages out there may have the data preloaded. But those are $$.

Out of curiosity - when you say "changes to make the suspension move correctly at lower ride heights", are you talking about modifying control arms and chassis mount points? There are a couple products out that allow you to drop the car a good bit and yet retain reasonable roll center heights without affecting bumpsteer.
Yes, that's exactly what I'm talking about doing. I just discovered the 6gun ball join extending products, and am very interested, but I want to carry things a step further, and incorporate those kinds of design changes into a larger product, perhaps with new LCA's with correct mounting points. Perhaps even a new upright setup providing for a new wheel bearing setup to correct that flex as well!

Interesting stuff, huh?
-Matt
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