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12/26/2011 6:05 pm  #1

Software Solutions for IRS design/Layouts?

As the title suggests – I've been looking for a solution set - to help me design and layout my IRS for  the 78 C3 Corvette.  My focus is (for the time being) is on a double wishbone setup, with toe-control, bellcrank to inboard shocks, and a fiberglass leaf spring (poor man's C5/6 IRS.)

I have already cut and welded metal for a "Jim's Giovanni" and my intention was to go with it and modify it later. But that "slippery slope" has me thinking; As long as the body is off - why not  get it closer and then be done with it?  So rather than just leap and cut - I've spent a bit of time crawling the web to find what is available out there to help design and layout my revised IRS.

Readings - A heap of those available - not  specifically covered in this posting -- except as how they might get to a solution set.
These are organized more in a cost high to low than utility - I haven't  the fiscal assets to try and compare all -- but wouldn't that be fun!

I found a few of the top end answers quickly with a bit of G00gleing:

Mitchell:  WinGEO3 - Suspension Geometry with Force-Based Roll Centers
Not cheap you'll note - but if it would save some pain of redoing - could be worth it.

It is much more robust that the simple screen shot above...
And the developer has some bit of experience.  He graduated from CalTech in 1967 with a degree in Mathematics specializing in numerical analysis,  That was followed with a Masters from Stanford University in 1969.  Extensive support throughout the Can-Am serioes during the 60s-70s, and a sponsor/judge for Formula SAE. 


Next might be Suspension Analyzer -

-- note  this is a front suspension - but will accomplish rear IRS too.
A nice thing about this software - you can apparently download it - give it a go - and if it is what you want -- then buy it.  Nice - EH?
From their website:

Suspension Analyzer v2.4 (Windows 98/Me/XP/2000/NT/Vista/Win 7)
The Suspension Analyzer is our most detailed, 3-D, double A-arm (wishbone) suspension analysis program.  It goes well beyond our simpler Roll Center Calculator to include steering inputs, bump steer (toe change), Ackerman, caster, anti-dive and much more.  Automatically "optimize" the
location of certain components for Roll Center location or minimum bump steer.  Shim the upper arm for certain Camber or caster.  Build graphs or reports from several user options, including graphs comparing 2 suspensions.  This program is available in 3 versions:
    Standard (front end only)
    Full Vehicle (front and/or rear suspensions, with additional features like roll steer, roll couple, anti-squat, pinion angle change, push rod and pull rod springs, and more)
    Full Vehicle with Data Logger Options (Full Vehicle version, but includes ways to import suspension measurements and ASCII data logger data from shock travel, accelerometers, etc and display the suspension motion, camber change, vehicle roll/dive/steer, track map, and much more)

Click on the blue link below and when asked, select Run to install it.   Program will run in Demo mode for free. If you like it, call Performance Trends with credit card information to order the standard working version for $249 or $399 for the Full Vehicle version, or $599 for Full Vehicle with Data Logger Options.

Performance Trends is one of the largest producers of high quality, high tech computer tools for today's racer, engine builder or performance enthusiast. Performance Trends started in 1986 with the release of our popular Drag Racing Analyzer computer program, quickly followed by the Engine Analyzer. Since then, we have expanded the product line to 20 engine building and racing computer programs.


You might get this one, SusPROG3D, confused with the Suspension Analyzer (above) as their pages have sort of a similar "look and feel."  As I recall SusProg is an Ozzie based development and has a number of built in options fto get you jump started.
There is an extensive set of Tutorials-- and an Evaluation Version - to try it out too. Purchase price is $300 US.  PayPay etc.

Here is a sample of a TuT form the website:

This is a basic "get you going" tutorial, using the registered SusProg3D software.

It is based on Chapter 7 of the book "Chassis Engineering" by Herb Adams ISBN 1-55788-055-7 Available from Society of Automotive Engineers  ( product code B-753) and BevenYoung

It is not necessary to have this book to use the tutorial, but Herb does discuss various design options and decisions, which may be useful.

You will need a registered copy of SusProg3D, version 4.500E (or later).
The evaluation version cannot be used for this tutorial because the evaluation version does not allow for changing the upright and wheel dimensions.

Start SusProg3D.

Umm Bummer - not fully implemented -- but understad the reasons why...


AutoWare is focused (IRS-wise) on 3 and 4 link styles.
And at $99.95 US -- not terribly expensive --- if a 4 link is in your plans. Note they have other software available too - for data acquisition and a number of other specific chores.


Now as I continued my "quest", I snuck over to see what was happening on the "LOCOST" forum. 
Got a couple of leads from there and chased those down too...

Here is "Speed-Wiz":
That screen shot sort of says it all, except who the developer is and how much it costs...

Development team

The development team leader, Bryan D. Feldman, has over 25 years of professional C/C++ software development experience. He is an avid auto enthusiast and fan as well as an experienced fabricator, tuner, and driver. He has been involved in the project from the very beginning.

All other members of the development and testing team are also experienced automotive and computer enthusiasts.

A YouTube Link too:

Oh - the price - at $29.95 - I couldn't pass it up -- still working it though as my preliminary to downloading a few of the evaluation versions above...

Well, at the "less than $50 we are in to the "free zone."
There are a few out there to work with and all have their +/deltas.  Haven't worked each yet - still gathering, cataloging, and getting ready to compare features (as time permits.) 


Suspension Calculator started as a Masters project:

The program not only eases suspension calculations, but also provides a teaching platform with diagrams and written explanations, to increase the understanding of the processes behind the results. Expect the diagrams and explanations to be available around the end of March.

As school projects are oft want to go - its been a few years and no updates from last year. Less than 20 posts on the Forum, but its free!

The BEST part -- It is where I got the lead on Speed-Wiz above!


Another one I found is "BonesApart"
It is easy to work - he built it for his Locost project, and it too is free.  From his site:

Strings n Things

"Just where should the suspension points go?" I hear you ask. Rush to your library and take out  Alan Staniforth's, Competition Car Suspension: A Practical Handbook.

This file is my take on the famous Staniforth string computer. It's a spreadsheet I  wrote earlier in the year that has proved to be very useful for estimating roll centres, camber change, track change etc.  The roll centre moves with suspension movement. It can't do roll axis, toe change or bump steer. The 3D maths of this is too hard and makes my head hurt. 

The file needs a reasonably recent version of Excel to run. Please enable macros when asked by  Excel. It's called BonesApart, which is a pun for both sides of the Atlantic and should even make the French happy. Click here to download. Feel free to distribute.

The first tab contains a list of instructions and an invite for users to donate beer.  The second tab is  the main work area. The third tab shows the instant centres and virtual swing arms.

As noted, there are a few limitations - but well worth spotting the Kiwi developer a beer!

There are a few other programs available - one is an online linkage movement set -  but it works "graphically."  By that, I mean - you move the points of attachment =- not by measurements - but the points.   I have misplaced my bookmark - but I found it only mildly interesting - but less useful to designing an IRS.

Speaking of "designing,"  there are a few YouTube videos (TuTs) of using SolidWorks (which I am familiar with) for IRS design.  Maybe Rhino too - (also familiar), but haven't dug that far.

BTW - I built and trialed a String Computer to work the Kinematics (2D) and I found it interesting and usefull.  It's always nice to play with paper and scissors -- DON'T RUN!

Anyone else find some useful progs out there? 
Share your thoughts and examples Please!

Cheers - Jim

Last edited by phantomjock (12/27/2011 5:20 am)

UNDERCONSTRUCTION! Highly Modified C3 Corvette
         Dual Wishbone IRS w Subframe + Custom Uprights

12/27/2011 3:19 pm  #2

Re: Software Solutions for IRS design/Layouts?

Once again nice thread!!!!  I really appreciate all the time and effort you put in to researching all this and the detail you used in sharing your info.  These are some fantastic tools.  Don't forget solid works it can also be used to analyze suspension geometry.  I am thinking I will have to look further in to some of the more less expensive options.  One thing is for sure there is nothing cheep about independent rear suspension

If it isn't broken..... modify it anyway!!!!

12/28/2011 3:50 am  #3

Re: Software Solutions for IRS design/Layouts?

Been fooling around with the BonesApart some and its easy-peasy!
I'm looking to spot the front roll center (there are a few mods already (SPC upper A-Arms, Vett Brakes Mono Leaf and lower AArms, andd a DIY Rack and Pinion.)  Want to clear the front before setting in on the rear.

When I get that sorted in BonesApart - I'll run again in Speed WIZ -- Stay tuned for details in a separate thread!

Here is a link to a pretty comprehensive Wheel/Tire Calculator:

Also there is an incredible set of software -- but at $1695 USD - you'd expect a lot!
Does complete chassis - front and rear as a SYSTEM!  Awesome. 
OptimumK   link:

They do have a 14 day trial -- with some limits - migh give it a whirl when better refined design.
And, if we formed our own "University" our  "team" could get it for $395!

Daze --
RE:  SolidWorks - found a nice link (I'll post a summary) describing how to use SW to work your suspension design.  As a part-time SW user - its something I've been drilling for a while.

Cheers - Jim

Last edited by phantomjock (12/28/2011 4:40 am)

UNDERCONSTRUCTION! Highly Modified C3 Corvette
         Dual Wishbone IRS w Subframe + Custom Uprights
     Thread Starter

12/28/2011 10:23 am  #4

Re: Software Solutions for IRS design/Layouts?

Doesn't Solid Works have a free design Jim. Someone posted this at Vettemod.


Last edited by Ralphy (12/28/2011 10:26 am)


12/28/2011 3:43 pm  #5

Re: Software Solutions for IRS design/Layouts?

EXCELLENT TIP!  Way  better than the one pager I was going to load...(may still get to that). 

Hey DAZE!  What about a downloads section for forum members to host ad DL from?  The site has an example or two for ideas.  Urges 'Lurkers' to joinup and if they're interested - eventually they'll participate too I'd bet..

Anyway, Ralphy's tip sent me on another drill down - and if you are a SW user - the FSAE handbook (198 pages worth) can be "previewed"here:

Covers a lot of the tutorials you'd find in the SW manuals - but focused on automotive applications -- specifically the Formula SAE.  In fact it appears to be a startup for the teams and assumes only very basic SW skills.  Good on them!

Should be very useful - and NOW - I have more on my plate!

BTW Ralphy:

Would you/could you capture the key dims from your C3  front end on the ground?  I need the Centerline to Upper & Lower A-Arms - Inside and Outside(the ball joint) , and  the height above ground for those points, and ditto to a common reference point - say, the lowest point on the chassis just ahead of the engine (the curve).   I've got a Rack and Pinion installed so can work from the common ref to get the tie rods and pinions at this end.  Send yours if stock.

Mine is up on 'horses and all measures are irrelevant - no engine, droop wrong etc.
In trade, I'll  model in BonesApart and Speed Wiz and post.  Getting the front ICs/RCs right will be usefull for both of us before modeling/fabbing the IRS. 

TIA, Mate.

Cheers - Jim

UNDERCONSTRUCTION! Highly Modified C3 Corvette
         Dual Wishbone IRS w Subframe + Custom Uprights
     Thread Starter

12/28/2011 4:18 pm  #6

Re: Software Solutions for IRS design/Layouts?

My Cobra has the Mustang II front suspension. So I am of no use there.



12/28/2011 5:05 pm  #7

Re: Software Solutions for IRS design/Layouts?

Copy and a C 4 IRS rear - Thanks mate.  'Splains the Avitar!

UNDERCONSTRUCTION! Highly Modified C3 Corvette
         Dual Wishbone IRS w Subframe + Custom Uprights
     Thread Starter

12/28/2011 7:08 pm  #8

Re: Software Solutions for IRS design/Layouts?

C3 Iron.


9/06/2015 12:26 am  #9

Re: Software Solutions for IRS design/Layouts?

Bought the Speed-Wiz basic package.
Liked that it does a lot more than just suspension.
Now to learn to use it!
Struggling to figure out how to input basic parameters.
Lots to look up, even arcane things like vehicle frontal area.

At these prices I want my gas 100 octane, leaded, and my windshield washed!

9/07/2015 12:43 am  #10

Re: Software Solutions for IRS design/Layouts?

Managed to model the rear IRS at least enough to get a starting point.
Need to make a basic change to correct positive outside camber gain in roll.
Started with parallel A arms.
Back to reading the book.

At these prices I want my gas 100 octane, leaded, and my windshield washed!

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