C of G - above ground (vehicle) 305.00 mm
            - above ground (sprung mass) 308.59 mm
            - from front axle cl 1348.15 mm
            - height above roll axis 232.65 mm
Single wheel rate - front - tyre 175.00 kg/cm 979.95 lb/in
                                          - spring 17.89 kg/cm 100.18 lb/in
                                          - arb 6.80 kg/cm 38.08 lb/in
                                          - combined 43.27 kg/cm 242.33 lb/in
                              - rear - tyre 174.00 kg/cm 974.35 lb/in
                                        - spring 31.12 kg/cm 174.26 lb/in
                                        - arb 0.00 kg/cm 0.00 lb/in
                                        - combined 52.80 kg/cm 295.65 lb/in
Anti-roll stiffness - front - on tyres 29936.76 kg-cm/degree 2152.76 ft-lb/degree
                                        - susp 4223.65 303.72
                                        - total 3701.43 266.17
Anti-roll stiffness - rear - on tyres 27677.54 kg-cm/degree 1990.29 ft-lb/degree
                                       - susp 4950.14 355.97
                                       - total 4199.13 301.96
Anti-roll stiffness - car - on tyres 57614.30 kg-cm/degree 4143.05 ft-lb/degree
                                      - susp 9173.79 659.69
                                      - total 7900.56 568.13
Weight transfer - front axle 92.81 kg 204.62 lb
                           - rear axle 114.33 kg 252.05 lb
Roll couple distribution 44.81% front
Roll angle - front - on tyres 0.43 degree
                             - suspension 2.05 degree
                             - total 2.49 degree
                 - rear - on tyres 0.56 degree
                           - suspension 1.93 degree
                           - total 2.49 degree

Susprog Software Data Input:

These are some of the most useful numbers we can calculate about your race car. 

You can see the relative roll stiffness of front and rear suspension.  The roll stiffness of springs and anti-roll bar are directly compared in the same units (the anti-roll bar stiffness adds to spring stiffness in roll.).  The roll angles, front and rear, are calculated for a given lateral acceleration (the unit is gravity - 1G corner, or 1.2G etc.)  Then, looking at other results from the suspension geometry analysis, you can determine if the car is likely to achieve that cornering force, or have the suspension numbers gone away to the extent that traction will be lost before reaching that roll angle?

See our theory section on this web site for a full discussion on weight transfer, and how to use the ideas for race car set up.

If the total weight transfer is distributed between front and rear wheel pairs in the same proportion as the front to rear static weight distribution, the steady state handling will be neutral with respect to weight transfer.   There will almost certainly be other oversteer and understeer torques to take into account eg the rear tyres may have a bigger footprint than the front.

We'd use these calculations as a starting point, if you asked us to specify springs and anti-roll bars for your car.   We can also look at the affects of changing key suspension settings, such as the roll centres.  If your race regulations allow freedoms in suspension design (say Sports Sedans, Tarmac Rally Cars, Open Wheelers etc) we could look at some of the parameters and priorities with you.  There's no need for any Designer's  "black boxes".

You have to ask yourself, how come there isn't more talk about these numbers in racing?  I guess, because you can't see them just by looking at the car (like some new component).  It's hard to imagine a serious race team that wouldn't like to look at the numbers for their car, though.

Wouldn't high end data acquisition tell me everything I need?  Data acquisition can help you with some of the input data you need, it can tell you about the results of changes you make, but not a lot about exactly what changes to make.  F1 teams still need the "shaker machine" to set the car up, even with the ultimate in data acquisition.  Motec say the most important aspect of use of their ADL Data Logger, is to have an experienced suspension set up person to interpret what's happening.

Even in the most restricted categories, these numbers tell you something interesting.  In HQ Holdens, for instance, you may want to know - " Would there be sufficient change in roll centres, and other geometry, such as dynamic camber, to justify experimenting with the allowed range of ride heights?"    It'd be good to do some calculations first, because changing HQ front springs is time consuming, and testing expensive.  Maybe a ride height as low as possible is always better, maybe not.

One interesting thing you find out when playing with the figures for road cars, is that the front and rear weight  transfers are often nowhere near balanced.  The old adage was that "they build them with lots of understeer so the average driver doesn't get caught with oversteer in an emergency".   So, you'd think they'd have lots of weight transfer at the front to create the understeer.  Right?  Wrong.  If the track is a bit narrow, the centre of gravity high and the weight distribution biased towards the front, you can't make the front roll resistance high enough on any reasonable road spring.  So they had to make the front suspension soft, create lots of roll and let the front "wash out", as the front tyres loose grip with excessive camber change and scrub.  You can see that it could be a huge error, when modifying an older road car, to stiffen roll resistance in the same proportion front and rear.  You could be a long way from the balance you want.

The advent of radial ply tyres with improved grip was the catalyst for change.  Look at any quality late model rear wheel drive road car.  The track will be wider, the CG lower and weight bias closer to 50-50.   The front anti-roll bar will probably be large diameter, working on a very advantageous lever ratio ie connected to the suspension as close as possible to the wheel.   It's not that the're trying to build a race car.  It's just that they have to do this to do this to create enough understeer, if they have good suspension geometry and want the good roll and pitch control now demanded by the customer.  So if we were modifying one of these cars, a straight percentage increase in front and rear roll resistance could be close to giving us a balanced race car.