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Frequently Asked Questions

Q: What does this software help me to do?

A: The software helps you avoid some very common mistakes in spring and sway bar selection. For instance, the spring rates (i.e. "stiffness") of the front springs needs to be matched to the rear springs to avoid "porpoising" which is an unpleasant "pitching" of the car over bumps, usually most apparent at a certain speed. The software also automatically makes the complicated calculations necessary to determine the "free length" a coil spring should have in order to achieve the ride height you want... like when you're lowering your car. The software is also helpful in modifying the car's handling characteristics — its relative oversteer and understeer. Or to retain the current handling while making other changes to the suspension like lowering it or making it stiffer. And the software can also help you when you're changing the total roll stiffness of your car when modifying the car for racing.

Q: OK, you've lost me. I don't even know what "rates" are or understand many of the other terms used on this website or in the manual.

A: I highly recommend that you purchase a book such as How to Make your Car Handle, by Fred Puhn, Tune to Win, Prepare to Win, or Engineer to Win (in that order) by Carrol Smith, and Secrets of Solo Racing by Henry A. Watts. They deal with information that is well beyond the scope of this website and the software, like driving techniques, shock absorber adjustment, suspension geometry and detailed discussions on vehicle dynamics and testing. There is also a website called Physics of Racing Series (here too, and here) that has helpful information (though it's mixed in with lots of highly technical math that you probably can skip over), and various websites like the San Francisco Region of the SCCA website that have useful information.

Q: How can this software calculate anything about my car?

A: You have to first make a number of measurements of your car's suspension and enter them into the spreadsheet. The spreadsheet uses your numbers to make the calculations necessary to determine the dynamic characteristics of your current suspension, and displays them for you.

Q: Can this software help me adjust my shocks?

A. No.

Q: Can this software help me design a suspension from scratch?

A. Not entirely. It will only help you with spring and sway bar rate selection, though it will take into account the geometry you decide upon. Others make software suitable for complete suspension design.

Q: I have no idea which springs and sway bars would work best for my car. How do I determine that?

A: The spreadsheets can only do so much. It's still up to you to make the final decision since only you know what is best for your particular situation. But the spreadsheets display the characteristics of your current suspension, and that, with advice from the manual as well as the "Advice" page, can help you decide. The Advice page discusses some of the more common suspension modifications and some of the advantages and disadvantages of them. And it also discusses the important aspect of how stiff they need to be, whether you're simply lowering your car, or trying to limit body roll or change the handling balance for racing.

© 1991, 1995, 1998, 1999 and 2001 Dennis Schøler Pedersen. The contents of this page, and the files linked within it, are copyrighted. Any unauthorized copying or duplication is forbidden by law.