Racing Car Technology
    Handling and Suspension Setup
     Street and Track  Suspension   
 
 
 

 

 

To tune the suspension on your car, weight transfer calculations are an essential first step.  For very low cost in both time and money, you can choose components that are compatible with the basic parameters of your car - eg roll centre heights, ride heights, track width, and weights.  You get a good baseline set up.  This way, you save cost in test time, and components that are not what you need.

Within the technical pages of this web site, we guide you through the process.  It's not hard to do, and no maths skills are assumed.  You only need the interest to get at the numbers that are going to help you transform the handling of your car.  

 

The Weight Transfer Worksheet (WTW)

With this important tool we can predict a suspension set up that will be balanced, based on pre-determined spring stiffness.  It applies for all cars.  For a "street and track" car, targa or performance road car, we use the same procedure as for a racing car.

The WTW was first developed for racing.  We needed a low cost procedure that would allow us to do a workshop set up, and then successfully track test.  Our "Weight Transfer Worksheet" (WTW),  now in use for some years, is validated for all types of racing cars - sports racing and open wheeler cars and particularly production based cars.

The example car we use to explain how to use the WTW, is in fact a standard road car - the Holden Monaro VZ CV8 6 speed.  As expected, for a modern performance car, the set up is balanced from the factory, and there is a clear development path for a "Street and Track" version.

The essence of the WTW worksheet procedure is the calculation of ride and roll rates (or suspension stiffness in bump/rebound and suspension stiffness in roll).  For racing and high performance, ride and roll rates are an essential part of the understanding of suspension set up: -
 

  • There is a range of stiffness that helps optimize tyre grip.
  • Need sufficient stiffness to control body movement in roll and pitch and keep suspension travel within reasonable bounds.  This is important.  A car on slicks with a lot of grip potential will require a lot more stiffness.
  • One element of determining the speed of response and driver feel.
  • Shocks have an important role to play, in concert with the springs in getting the tyres to work.

    If you subscribe to the web site, and are doing a WTW for your car, we will discuss with you what your suspension stiffness options are.

The "ride rate" is expressed as the spring frequency, in cycles per minute (the number of times the car will bounce up and down in one minute if there is no friction and no damping from the shocks).   See the the demo videos on the bounce test, and suspension frequency on the home page of this web site).  Spring frequency is comparable between all race cars.  As an example, we might set up a performance road car, used for tarmac rallies, with 115 cpm front spring frequency, and 110 cycles per minute rear spring frequency.

The "roll rate" is expressed in degrees of body roll per unit lateral acceleration (degrees per G).  For our above performance car, we might look for a roll angle of around 3.0 degrees per G.

The balance of the car is indicated by the "magic number", a measure of percentage weight transfer at the front compared to the static front weight percentage. 

Now we can try different springs, anti-roll bars and roll centre heights in the WTW, and see what combinations will produce the ride and roll rates we want, while maintaining a good balance for the car.  It is clear that this is an extremely valuable exercise.

Ease of measuring and weighing the car, and clear instructions to enter the input data is a hallmark of the WTW.

To begin the set up of your car with the Weight Transfer Worksheet, please go to our subscription page.  We offer our assistance by email, to have a look over your numbers, and make some suggestions for the car.  We offer a 100% money back guarantee, if our procedure does not provide good and valuable information for you.

Note:
The WTW is still of value for racing categories with fixed suspension package eg Saloon Cars, Brute Utes or Carrera Cup.  You can use the WTW to check the "natural" balance of the car, and optimize ride height (and roll centre inclination) in a workshop set up.  By measuring on the car, or with the help of a suspension geometry program, such as Susprog 3D, or especially Claude Rouelle's new kinematic program you can see if your proposed ride height suits the camber and bump steer curves.  (The camber and bump steer curves might be fixed by the standard suspension components.  But by looking at ride height options, you can choose where your suspension movement is on those curves.)  

Discussion on the Origins of Weight Transfer Concepts.  How Does the WTW Work? 

What You Will Know if You Do a WTW for Your Car

10 Biggest Set Up Mistakes  Thought starters about weight transfer issues.

  

  

 

Optimum G
Claude Rouelle is founder and CEO of Optimum G, a company that provides technical training and consulting services for
professional racing. He runs seminar training courses for race engineers.

We are applying the work of Claude, Mark Oritz, David Gould and many authors, such as Carrol Smith, Bill Milliken, Alan Staniforth and Paul Valkenburg.  Angelo Tempia's seminar through the SAE-A was also extremely valuable to us.

So it is our goal to make all essential theory and practice accessible through this web site, to all racers and all workshops who require it. 

 

 

 

 

Different Drivers
Different drivers use different set ups to achieve the balance that suits their own driving style.  It is often noted that Craig Lowndes is generally quick on corner entry - at turn in and up to corner apex.  Mark Skaife in his book says of when they drove together for HRT "Even though our cars were identical in every other way, Lowndsey and I always found that Craig preferred his car stiffer in the back than my car."  The difference in set up was usually the next stiffest rear spring for Craig. 

The WTW helps us look at the factors and their  combinations that will influence the balance of the car eg rear roll centre height, spring rates and ARB rates.