PART 1: Perfecting Your Car Control - How Do You Feel What the Race Car is Doing?
Racing Car Drivers...
Here's How to Perfect Your Car Control Skills
In this three part series, we show you some new insights you can implement in helping you perfect your car control skills:
Perfecting Your Car Control Skills PARTS 1,2 and 3
PART 1: How Do You Feel What the Race Car is Doing?
PART 2: "Black Box" Car Control
PART 3: Trail Braking and "Zero Steer" - Two Sides of the Same Chassis Rotation Feeling
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There is one aspect of car control most associated with the best racing drivers - the driver must have "good feel for the car".
Yet one of the biggest stumbling blocks, the thing that vexes racing drivers the most when trying to improve their car control, is that we just don't know what it is that the racing driver is feeling.
What if you could know what it is you are “feeling” in controlling the race car?
That could help you build confidence in your skills, wouldn’t it? It could even form the basis for a whole new approach to how you develop your skills and drive the race car.
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There’s new information from the world of cognitive science as to how racing drivers learn and perform the actions required in controlling the race car:
The race car can be considered an extension of the driver's body. Like any type of vehicle - cars, aeroplanes, bicycles, skateboards, skis - for the driver, pilot or rider, they all modify our capability to move in three-dimensional space.
The foundation of the racing driver's sensitivity is based on an advanced level of hand-eye co-ordination - syncing vision with the motor skills required in controlling the race car. With practise and repetition, the driver achieves a level of muscle memory where mental processing of the visuals with the relevant driver actions is carried out without conscious effort.
Open Loop vs Closed Loop Control
We can refer to the above visual/ muscle memory mechanism as “open loop control”. The racing driver's subconscious store of knowledge performs the greater part of car control.
By comparison, "closed loop control" is where we have a viable feedback signal allowing the racing driver to make continous, fine, and accurate adjustments to the speed and path of the race car.
(For more on open loop control see Perfecting Car Control Part 2: "Black Box Car Control").
Closed Loop Car Control
In addition to the vision/muscle memory mechanism, the driver's subconscious brain will seamlessly process information from all the other senses.
Given the nature of the mental processing, we cannot say exactly what the subconscious will take note of, or what it will ignore, except to suggest that the highest value sensory information is related to feeling motion, a feeling for the longitudinal g-force of accelerating and braking, the lateral g-force of cornering, and especially rotational acceleration around the centre of gravity.
In cornering, the lateral G is easily felt by the driver, building up in the corner entry to a maximum mid corner and then letting go in the corner exit. But the signal, the feeling the driver gets, doesn't relate well to that moment in time when the race car loses grip - not a good enough signal for workable closed loop control.
However, the rotational motion feeling, the feeling of the race car rotating in the oversteer direction, does hold promise for closed loop control of the race car. It is as an instant message, direct from the tyre contact patches and highly relatable to the loss of grip at the limit.
Our Key Concept in Car Control:
The Racing Driver's Primary Feel
for the Balance of the Race Car…
How the racing driver feels what the race car is doing is, for the most part, clouded in mystery. Over the history of racing, there's been very little commentary from racing drivers on this.
This quote from Lewis Hamilton is tantalizing and may be unique. “It’s the motion of the car that tells me how fast or how slow I’m going towards the apex of the corner – gives me the feeling of when to push.” From the YouTube video “How to Drive Like Lewis Hamilton”.
I think the motion Lewis is talking about is this tiny, abrupt rotation motion of the chassis that occurs as a result of tyre slip angles and grip building at the rear of the car. It’s your feel for the balance of the race car. It’s the motion that gives you the feeling of knowing you are pushing to the limit of grip of the tyres.
You don’t have to think about your speed - whether you can go faster in the corner entry – just manipulate the balance of the car to cancel out any understeer and push until you feel you are at the oversteer limit of grip of the rear tyres. That will be the fastest you can go for the line you have chosen in the corner.
It can feel something like the rear tyres starting to slide. Most racing drivers assume that to be the case, when, in fact, the feeling is in advance of the rear tyres sliding.
Why Hasn’t Information About This Rotation
Motion Been Available for Racing Drivers Before?
This tiny rotation of the chassis due to rear tyre slip angles is so obscure and minute that the feeling of the rotation cannot be top of mind - not something we can identify by thinking about it.
In my own racing, I used to wonder “Why can’t I remember much about what happens during a race, given that I’ve been concentrating so hard the whole time?”
The reason is that the greater part of the processing and outputting of the necessary actions in driving the race car are not available to our conscious mind.
In the absence of any trusted knowledge about the vehicle dynamics involved, it’s natural for us to mind engineer stuff and come to our own conclusions. Over time, a lot of not so useful ideas get traction with the racing community, making it even less likely we’ll discover the truth.
Neither have engineers told drivers about this. This tiny rotation motion, and the associated drift angle, known as the vehicle slip angle or body slip angle, is very important in vehicle dynamics. It is well known to the vehicle dynamics engineers in terms of the modelling and calculations they do. But it has not been previously presented as the primary source of driver feel.
As far as I am aware, there is only one vehicle dynamics book that discusses this - “The Multibody Systems Approach to Vehicle Dynamics” by Mike Blundell and Damian Harty. (There are references in the book that support the essential elements of driver control as we show you here.)
How Do You Feel and Respond to Oversteer?
Anecdotally, I think we can say that the primary feel for the racing driver is high sensitivity to any sudden changes in the oversteer rotation motion of the race car. How else can you respond so quickly with the necessary counter steer when the rear of the car lets go? Your response to the rotation feeling is way ahead of what you see happening with your eyes, for example.
(Your feeling for weight transfer, roll motion and lateral G, - these are all feelings that may contribute to general open loop control of the race car, but do not have the definitive feedback mechanism available when feeling the rotation motion.)
At the limit of grip, the racing driver can monitor the balance of the race car based on how lively the car feels - how willing to turn. It is an instant indication of the balance of the race car. The racing driver’s internal gyro almost instantly picks up on the oversteer rotation as a direct message from the tyres.
Up until recently, we were dancing around the edges of this rotation feeling. We didn’t understand that the feel for grip via the tyres slip angles is actually coming from the rear of the car only.
But now the mechanism is clear…
As you turn the race car into the corner, there is a tiny abrupt tweak of the chassis in the oversteer direction as the rear tyre slip angles go from zero to peak slip angle (i.e. zero to maximum cornering grip).
As a result of the rotation motion, the race car adopts this drift angle, or nose in attitude, relative to the direction of travel (the body slip angle). (You can see the body slip angle in photos of race cars approaching the apex of the corner.)
The rotation feeling is due to the chassis rotation motion caused by elastic twist in the side walls of the tyres between the contact patch and the rim. The rotation happens as tyre slip angles build at the rear of the car only. (Nothing to do with the tyres losing grip.)
(At the front, side wall twist is taken up by steering a little further into the corner, something the driver doesn’t particularly notice through the steering and has no effect on the chassis rotation.)
There's one reference in the vehicle dynamics text books that supports the above explanation, “Race Car Vehicle Dynamics” by Bill and Doug Milliken, page 131, “The entire chassis rotates an amount equal to the rear tyre slip angle…. This rotation establishes the attitude of the machine to its path.”
The feeling of the oversteer rotation is delivered instantly to the driver and the feedback response is equally immediate, resulting in finer and finer control of the race car. i.e. The driver's assessment of the rotation is not that accurate in the first instance. It is the continous instant feedback coming from the tyres that improves the accuracy of the driver responses.
The Chassis Rotation Motion and Feeling For Balance
It’s a feeling for the balance of the car where the car feels either…
- too lively (agile), wants to turn too readily, prone to oversteer
OR at the other extreme
- too stable, the car feels sluggish, too much understeer
Perfect balance is a little less than too lively. You feel good response with sufficient stability. i.e. the motions of the race car are happening within your ability to control them. When the car is responsive, it is easier to make small corrections in the corner. You can iniate rotation and stop rotation quickly
On the other hand, if you are too far into the stable area of the handling window, you may not feel the rotation from the rear tyre slip angles and therefore, you are not able to control the race car with the same precision you have with the more agile set-up .
In the corner entry, you manipulate the balance of the race to reduce understseer and push until the rotation motion is felt. If the car feels too lively, this is a pre-warning of oversteer about to happen. (For more on feeling and manipulating the balance of the race, see Part 3 of this series on Perfecting Your Car Control: "Trail Braking and Zero Steer - Two Sides of the Same Chassis Rotation Feeling".
In controlling the race car, the initial feeling of agility comes via the chassis rotation due to tyre slip angles building at the rear tyres. The tyres are not sliding. The rotation motion of the chassis on the tyres fmay feel to the driver like it is the beginning of sliding, even though the rear tyres are still gripping the road.
Learn More at Our Car Control Workshop 2023
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