This flow chart summarizes the thinking and procedures needed to set-up the race car as per my new E Book "The 7 Little Known Hacks...".
But would you need to have that level of understanding about how the race car works? Could not the highly skilled and experienced racing driver say what's needed for the car to make it go faster?
Race driving is a confidence game. As you get more experienced in racing, you get to be highly confident in your ability to control the vehicle at the limit of grip. This can easily give you the feeling that your racing skill should help you with setup - help you work out what is happening and how you could improve the car. But this is not the case.
Race driving ability and set-up know-how are almost mutually exclusive.
The talented racing driver is highly skilled in going quick around the race track.
But clearly, driving ability does not depend on knowing the ins and outs of how the race car actually works. The driver just responds and utilizes the...
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...
For a new race car, an important early decision in the design process is the choice of front to rear weight distribution.
Equally, if we are racing an existing car it’s important to know what our weight distribution is, so we can make decisions about the suspension set-up of the car.
How do we measure weight distribution?
If we have the corner weights, we can determine the weight at the front and rear axles as a proportion of the total weight. E.g. We may have 53% of the total weight at the front axle, leaving 47% of the total weight at the rear axle.
How does weight distribution affect the balance of the car? What is the effect of more front weight? Or more rear weight?
To get answers to these questions, let’s look at the problem from the vehicle dynamics engineer’s perspective. They are trained in the application of a universal simple model of handling known as the “bicycle model”.
Here is a schematic diagram describing the main features...
The details of anti-roll bar operation are discussed in our blog article, “Anti-Roll Bars. A Good or a Bad Thing?”
As indicated in that article, there’s much more to anti-roll bars than simply reducing body roll.
In this blog I want to focus on two super important characteristics of anti-roll bars in suspension set-up for racing…Suspension Stiffness in Roll and How You Get More Grip With Stiffer Springs and ARBs.
Suspension Stiffness in Roll
The anti-roll bar adds to suspension stiffness in roll i.e. In cornering, both the spring and the anti-roll bar contribute to the suspension stiffness as seen at the tyre contact patch.
I’m going to quote a vehicle dynamics expert here, so you don’t think I am making this up:
“Typically, a bigger bar on the front improves the perception of nimbleness, (agility), as it makes the outer tire work harder in the first half a second or so (of initial turn-in).” Greg Locock – Engineering...
In racing, it’s often thought the tyre slip angle is an indication of the tyre losing cornering grip – that the slip angle is formed by the tyres “slipping” or “sliding” on the pavement.
The truth is, tyres build grip with increasing slip angles up to the point where grip starts to level off, as shown below in the slip angle vs grip diagram.
It's important to understand a little about how grip is created at the tyres.
A steering control input from the driver results in the forward momentum of the car being counteracted by frictional forces acting at the tyre contact patches, and so creating tyre slip angles at the contact patches as the car starts to turn and build cornering grip in the tyres.
Tyre slip angles are a property of the pneumatic tyre that creates the lateral force and allows the car to turn. (If we had steel treads, for example, there would be no slip angles, and insufficient friction available to create a...
How much do we need to know about the physics of race car handling?
There are two sides to this:
So, Race Car Handling and Suspension Set-Up is a pretty thorny subject. Right?
I’m having a crack at it in my new E Book “7 Little- Known Hacks – Your Pathway to Race Car Handling Mastery”
I’m especially not making it hard to understand with too much mathematics.
However, I’m mindful of the quotation attributed to Albert Einstein, “Everything should be made as simple as possible, but not simpler”.
So, you'll need to put in the...
It’s no good making random adjustments to your race car set-up at the race track. You'll most likely get lost with the changes you make, and end up not making the car any faster.
Magazine articles, "cheat sheets", and generalized advice you get on set-up from internet web sites, are particularly unhelpful. No wonder the general impression most racers get is that handling, as it applies to set-up, must be very complicated.
Even someone highly experienced both as a driver and a set-up engineer cannot tell what you need straight off. They can't just jump in your race car, do some laps, and then say you need XYZ springs and anti-roll bars.
What you need is a baseline set-up. The set-up we know is close to optimum. Then in testing, you and/or your team, can decide what changes you’ll try.
At Racing Car Technology, the baseline is the set-up we can do in advance in the workshop, then go to the track knowing we are in the set-up...
Here's the full version of TRE's video of this tarmac rally car on their 7 Post shaker rig:
TRE Dynamics are technical partners with Ohlins DTC, Germany.
You can see in the video, the shaker rig forcing vibrations in the suspension. About half way through, they show you a "track replay". The actual suspension movements from the track are reproduced.
Best dynamic grip comes from minimizing the tyre load variation, minimizing disturbance, minimizing vibration at the tyre contact patch. (Note the difference in shaker rig testing for road cars. The required set-up will be a compromise between ride quality - least disturbance for the driver and passengers - and best grip - least disturbance at the tyre contact patch.)
To minimize disturbance at the tyre contact patch, you need the required "natural suspension frequency" or "suspension frequency", as we regularly call it.
The "natural suspension frequency" is the vibration of the suspension...
Race car handling is about optimizing the behavior of the vehicle in response to the driver inputs.
So, if we're going to truly understand vehicle dynamics, we have to look at it from both a vehicle setup and driver control perspective at the same time:
At the bottom of the diagram, the car is traveling slowly. The car can turn sharply, but there is no rotation of the vehicle about its own axis.
In the middle diagram, cornering at racing speeds, there is rotation as the driver turns in. Then, as the car takes a set in the mid corner, the rotation stops. The race car has adopted a nose-in attitude, as shown by the "vehicle slip angle", β.
In the top diagram, the rotation has not settled by the mid corner. The rotation keeps on going and the car has gone in to a spin, as indicated by the now much larger vehicle slip angle.
The interconnection between the vehicle dynamics and...
Weight Transfer Part 3: How Does the Driver Control the Race Car?
This is the final part in our “Weight Transfer” series. See Part 1 and 2 home page /blog
Summarizing what we discussed in Parts 1 & 2:
Nowadays, “weight transfer” thinking is commonly used to describe what the racing driver is doing. The driver is said to manage or control the weight transfer. The “rate of weight transfer” is considered important. And as discussed in Weight Transfer Part 2, the driving coach Rob Wilson talks weight transfer almost exclusively when he describes what he is teaching to drivers.
Talking “weight transfer” with respect to race driving is a fairly recent phenomenon. Most of the authors of books on handling don’t talk about weight transfer in the context of the driver controlling the car.
My major sticking point with weight transfer thinking is that drivers cannot feel...