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.
The idea is that if we were to 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, 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? 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 “Every Racers Guide to Suspension Tuning”, we assist you every step of the way.
You’ll know already from our free training Suspension Tuning 101 and 102, that 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.
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. Sure, there’s some interesting theory in our course – again, all from the driver’s point of view. But our core promise is that you will be able to do a Weight Transfer Worksheet™, 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.
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