Does anyone have a program that can analyze the characteristics of our suspension or know of such quantitative data? I am interested in developing a good starting point for the modification of our suspensions. I know the usual aftermarket stuff is available but I have read where many racers change the mounting points and even the length and shape of control arms.

I am assuming that for liability reasons any production vehicle is designed to be safe for drivers from teenagers to grandmothers and for loads from one to five person plus luggage. That would seem to leave room for significant optimization potential for individual drivers.

As and example this diagram shows a static graphical analyses. If the inner mounting of the lower arm is raised this would shorten the lever arm between the CG and RC to reduce body roll. However, suspension characteristics are all interactive so the effects on steering, contact patch, etc would need to be determined.

Here it is.


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'80 DL 2 door, '89 DL Wagon

Indeed, check out TurboBricks... lots of collective experience/experimentation over there.

Check out www.trianglesunlimited.com. He's got some pretty neat stuff.

You're kinda limited with mounting points on the car, without coming up with major tweaks to the unibody.

-Ryan
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Athens, Ohio
1987 245 DL 314k, Dog-mobile
1990 245 DL 134k M47, E-codes, GT Sway Bars, GT Braces, Draco Wheels
1991 745 GL 300k, Regina, 23/21mm Turbo Sway Bars

Second attempt at getting the diagram from the technical photo gallery to here.

I don't know if they have the exact info you're looking for but turbobricks is a great resource for brick buildups.

Thanks for the links. That is a lot of very nice stuff. I have not done an exhaustive review of every write-up and thread on turbobricks. All of these suspension products and modifications deal with static settings or the dampening and stiffening of the stock geometry.

I believe the stock suspension does not change the camber enough to compensate for body roll. That is, as the body rolls in a turn, it tilts the tires as well thus increasing the positive camber of the outside tires. As the body rolls the outside suspension compresses and the geometry changes the camber to compensate but not enough to keep the tire vertical. Thus in a hard corner we get increased positive camber and excessive understeer. I hope I got my polarities right.

P.S. Could somebody help me get my diagram from the technical photo gallery?
“Strut Suspension Geometry”
http://www.brickboard.com/GALLERY/images/8736.gif

The common way people are dialing in more negative camber is to install camber plates. Check out TrianglesUnlimited.com. If the car is not tracked all the time the excessive negative camber will wear the inner edge of the tire during normal driving. You can have a volvo with a pretty trick suspension. I have a riend with a 242 with full coilover suspension. Check out colemanracing.com they sell different length and pound springs to mix and match. HAve fun and go fast.

Great links, thanks. However, those compromises are what I am trying to avoid. Trading angles at one point, straight, for better angles at other, turning. I am trying to determine what components such a suspension arms need to be changed in length or mounting points to optimize a particular use of the vehicle, sport driving. In order to do that I need to figure out numerically what the suspension is doing in stock form. Then try to find a better compromise for my particular need.

The answer is/was made by Volvo--it's called the 140--with A arm suspension in front. -- Dave

Yes, double A arms are considered best for performance vehicles. I still think for liability reasons the engineers would have designed in excessive understeer. As may be obvious my interest is in dry or lightly wet conditions. Volvo has always been all about safety. "Excessive" understeer is safest for inexperienced drivers and in snow or ice.

By the way, there was a special on the history channel about Volvo. Anyone catch it?

While it's true that understeer is considered the safest handling characteristic for average drivers--and Volvos have always had that at slow speeds--some models have more than others. The 544,122 and 140 all have terminal oversteer with each succeeding model less so. By the time 240's came along the understeer became predominant. The 940 Turbo I drove for a while felt great at 5 or 6 tenths but seemed to want to grind the tread off the front tires if pushed. It may be fun to fantasize about a "great" track worthy suspension for the 240 but there are the bits out there to make one competent for a reasonable amount of money. An ex ITB (142) racer I know has developed his 244 daily driver into a competive time trial car with carefull selection of parts and some clever hand fabrication without going to the extent and expense of redesigning the chassis. Now I suppose you could build a tube frame GT class car draped with a 242 body. --- Dave

Fantasizing is fun but no, I really don't want to go as far as track worthy modifications. I think your word competent is what I'm after. Competent for my style and conditions on the road. If it were also competent for time trails that would be great.

I want balanced handling for a reasonable cost and a little clever design. However, before I make changes I need to know where the weaknesses are in 240 suspension geometry. Hence, my original request for a program that could analyze a suspension's geometry changes during body roll, bounce, rebound, etc. It is I think a problem in mechanical statics where you have to figure out the angles and loads for each increment in a linkage system.

It would seem the technical/engineering challenge is where you are going to get your satisfaction. The basics of making a 240 handle are the same for any car with strut suspension so to go beyond that requires more than a passing interest in suspension design--I admire you for that. Myself, I'm impatient and would look to assemble a collection of pieces that will complement and work with each other--spring rate, ride height,shocks,bars, alignment and maybe camber plates--all stuff you can tailor to your needs. Out on the road you can make great strides with available parts.
Beyond the 8 tenths level of driving where the type of changes you propose will make a difference would put you into the "menace to society" category--doesn't sound like that's where you're at. -- Dave

You are right, I'm not looking to drive 10 tenths to the grocery store. The analysis stuff is also difficult. I've tried measuring arm length to the center of a ball joint with a tape measure. It is not very accurate.

See my reply to your original message.
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'80 DL 2 door, '89 DL Wagon