How to Choose Your Racing Springs - Racing Car Technology's Bounce Testâ„¢

How to Work Out What Racing Springs You Need....
First step is to work out the "suspension frequency". 

Decidedly low tech....  But way more important than I thought over 15 years ago, when we first came up with the idea.  It's been the key to developing the Weight Transfer Worksheet™ for use on production road and race cars.

For racing we want higher spring frequencies to create more grip at the tyres.  As the tyre cycles up and down due to the road surface, there is a degree of stiffness that helps the tyre key better into the road surface and give least "contact patch load" (CPL) variation.  The beauty of the suspension frequency measurement is that it is directly comparable between all race cars, so we can predict what spring frequency is likely to work best. 

To measure the spring frequency with the Bounce Test, the idea is that if we push the car down and there was no friction or binding, then it would continue to bounce up and down forever at its "natural frequency".  In the real world of course, the car settles quite quickly due to friction, as you can see when I pushed the car a couple of times at the beginning of the video.

If I push the car down each time it comes up, what happens?  I can keep the bounce test action going by overcoming the friction in the suspension bushing.

It's well known in engineering terms, that friction reduces the amplitude of the "vibration", without much affect on the frequency.  So what we are looking at with the Bounce Test™ is the "undamped natural frequency of the sprung mass."  (I hasten to add that damping from shock absorbers will slow down the frequency, either a little (low damping) or a lot (higher damping).

Our Bounce Test™ is one of two basic procedures we use in getting the data we need for the Weight Transfer Worksheet™.  (The other is measuring the Motion Ratio for the spring where we have coil-overs, and therefore cannot remove the shocks to do the Bounce Test™.)

Why is the Bounce Test™ so important?  Because it gives us a direct read of the suspension frequency, front and rear, our most important number, and the starting point in setting up the car.  And nothing could be simpler, as you see in the video.  Right?

There are fine nuances and things you find out when you try this out.  In our training course “Get More Grip and Better Balance”, we assist you every step of the way by having a comment section at the bottom of every page where you can ask questions and get prompt answers, generally within 24 hours.    

Optimizing suspension stiffness is where the speed comes from in all our setups for the track.  We then have a good handle on what the setup might be like for any road going version of the same car. (The road car will generally need softer suspension so that the ride can be acceptable).

I wouldn’t be surprised if you’re asking yourself, why don’t I hear more about this from suppliers of springs and shock absorbers in the market place?  I don’t know for sure, but I think part of the answer would be the enormity of taking it upon their business to properly educate their customers.  If the shock supplier said, “Could I have your motion ratios please?” the most common response would be “Huh?”.  I see many instances where the supplier has not  attempted even a quick guess at the motion ratio – which begs the question, "Do THEY know about it?"

Talking to the Boss of high end racing shock supplier Black Art Designs, some years ago, he had a big push on at the time to give training to the race teams who were running his shocks.  Now, he was charging £1,000 for the course in the UK.  You pay a lot less with us – but this just gives you an idea of the premium that applies to this sort of information generally.

And in our case, we want to make it easy for you to do this.  Our core promise is that you will be able to do a Weight Transfer Worksheet™ for your race car, and make meaningful decisions about your car set up.  Even if the intracies of the suspension are not your thing, and others are doing the work, you will still be able to instruct them as to what you want.

Check out our new E Book:

"7 Little-Known Hacks - Your Pathway to Suspension Set-Up Mastery."

The "7 Hacks..." are seven little known insights into race car handling.  A unique overview of handling that could transform your understanding of what’s required to do your own suspension set-up.

We take a deep dive into how race car handling actually works.