How to Choose Your Racing Springs - Racing Car Technology's Bounce Test™

Uncategorized Feb 06, 2020
 

Most racers realize their choice of suspension stiffness, the spring rates they choose ie (say in lbs/in, Kgs/mm, or N/m)  are important.

In fact, for low or non-aero race cars, at Racing Car Technology, we have found choice of the suspension stiffness is the most important setting on the car for improving grip at the tyres and optimizing performance.

When buying suspension springs, how do you know what spring rates to order?

Parts suppliers, shock absorber and suspension specialists, and car preparation shops are likely to make a the choice for you, unless you say what you want.

Yet, even with very experienced people making the decision, most racing car spring selection is little more than informed guess work. It doesn't need to be that way.

In racing, it's the stiffness of the spring that counts.

What we’re showing you in the video is a unique way of measuring suspension stiffness.  We’ve called this simple test the Racing Car Technology  Bounce Test™.

The recognized measure of suspension stiffness is the "suspension frequency". Or as I call it in the video, "spring frequency".

What we are after is the spring rates we need to achieve our desired suspension frequency.

With the Bounce Test™ above, for this Triumph TR3 race car, we have 122 cycles per minute (CPM) spring frequency, with 550 lb/in springs in the car.  If we want to go stiffer, say 130 CPM, we can work out the spring rates we need to do that in a simple Excel spreadsheet. 

Getting the right spring rates in the car is a huge factor in optimizing grip at the tyres. For us at Racing Car Technology, it’s the single biggest improvement we make to non-aero race cars. The single biggest contributor to improvement in lap time.

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On the road, it's the springs that give the suspension compliance necessary to isolate the passengers from bumps in the road surface. i.e. Soft springs are needed for good ride.

But in racing, we don't care about a comfortable ride for the driver. We're only concerned about getting the suspension stiffness higher (by fitting stiff racing springs) so we can get more grip at the tyres. To give you a feel for how stiff we are talking about here, we’ve found for production race cars, the springs needed for best grip will be around 2 - 4 times stiffer than the standard springs. 

Our Bounce Test™ is one of two basic procedures we use in determining the suspension frequency. The other requires measuring the Motion Ratio for the spring. We need this for coil-over suspensions where we 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?

Well, there are fine nuances and things you find out when you try this.  It's our experience with the Bounce Test™ over nearly twenty years that gives us confidence in the recommendations we make.

Now you can get a perfect handle on what you need for setting up the suspension on your own race car with Racing Car Technology's online training programs. A big part of that is working with the Bounce Test™. We have added a new dimension to spring selection for production race cars.

Here you can see an overview of our full set-up procedure at Racing Car Technology....

Get this free report: "Our Racing Car Technology BLUEPRINT for Getting a Great Suspension Set-Up."