“WHEN THE STUDENT IS REALLY READY THE TEACHER WILL APPEAR” - -Lao Tzu

HOW TO TEACH YOURSELF HEEL TOE SHIFTING

By Art Meltzer

For those of us that drive cars with three pedals, heel-to-toe shifting (HTS) is an essential component of HPDE.  HTS is a complex maneuver that requires precise footwork coordinated with an awareness of engine rpms that is performed during heavy braking while preparing for a corner.  It’s no surprise that many drivers find HTS difficult to learn and to perform.

This article will discuss the consequences of downshifting without HTS as it relates to the impact on the car and the driver’s ability to negotiate a corner and present a stepwise and safe technique to teach yourself HTS.

Simply put, the engine converts the potential energy stored in the chemical bonds of gasoline into kinetic energy in the form of a rotating crankshaft and flywheel.  The car’s transmission consists of an input shaft (IS), internal gearing, and an output shaft (OS). The IS is driven by the engine when the clutch is engaged and the OS is mechanically connected to the axles, wheels, and tires.  The tires connect the car to the road. The internal gearing of the transmission translates the rotational speed of the IS to the OS so that the rotational speed of the OS provides maximal mechanical advantage to propel the car.  

The clutch consists of the clutch pedal, clutch springs and the friction disc.  The friction disc is mechanically connected to the IS and contains friction material that allows the friction disc to grip the rotating flywheel.  When there is no pressure on the clutch pedal (meaning the clutch is engaged) the clutch springs press the friction disc against the flywheel so that the friction disc and the flywheel are locked and rotate in unison.  Stepping on the clutch pedal moves the friction disc away from the flywheel. With the clutch pedal fully depressed the friction disc is completely disengaged from the flywheel so that the engine is mechanically separated from the drivetrain.

SHIFTING WITHOUT HTS

Let’s say a car is traveling at 110 miles an hour in fifth gear approaching a turn. You want to downshift to third gear and enter the turn at 50 mph. Also, assume that at 50 mph in third gear with the clutch engaged, the crankshaft, flywheel and IS all rotate at 4500 rpms. 

At some point after beginning braking, the driver must downshift.  Let’s assume that the driver downshifts when the car is traveling at exactly 50 mph and the engine is at 4500 rpms.  Without HTS the sequence of events involved in downshifting consist of depressing the clutch pedal, moving the stick to third gear, and releasing the clutch pedal.

In the time it takes to depress the clutch and move the stick the engine will slow to idle speed, approximately 850 rpms. At the same time, the transmission is mechanically connected with the rear wheels that are travelling at 50 mph.

With the transmission in third gear, and the rear wheels (at 50 mph) driving the OS, the internal gearing of the transmission causes the IS and the friction disc to rotate at 4500 rpms.  This differential in rpms between the friction disc and the flywheel (in this example 4500 rpms vs 850 rpms) is referred to as rev mismatch.

With this degree of rev mismatch, no matter how carefully the clutch pedal is released, there will be a forceful and abrupt exchange of energy between the rear wheels/transmission/friction disc (high energy) and the engine/flywheel at idle speed (low energy). The energy is transferred through the drive train and results in a powerful braking effect on the rear wheels as the car’s momentum is utilized to increase the engine rpms. This is referred to as engine braking. The powerful and jarring forces of engine braking are damaging to all of the components of the drivetrain, of many of which are delicate and expensive to repair.

There is significant forward weight transfer with engine braking. This forward weight transfer causes the nose of the car to dive and the rear end to become light. Sometimes the rear wheels will momentarily lock up. All of this occurs under heavy braking just before turn-in at a point in which proper balance of the car is essential and the driver’s concentration needs to be focused on negotiating the corner. Needless to say, unsettling the car and distracting the driver just before corner entry is not optimal.

Because of this, some drivers that do not utilize HTS will delay downshifting to just before turn-in to minimize the detrimental effects of rev mismatch. This may lessen the magnitude of engine braking but does not resolve the issue.  

HEEL TOE SHIFTING

HTS eliminates rev mismatch by blipping the gas pedal with your right foot just as you’re releasing the clutch pedal at the same time your right foot is applying pressure to the brake pedal. This is harder to do than patting your head and rubbing your tummy at the same time.

I will refer to using your right foot to simultaneously brake and blip the throttle as the “one foot, two pedal” (1F2P) maneuver.

REV MATCHING

Rev matching corrects rev mismatch.  In the example above, the rev mismatch consisted of the friction disc rotating at 4500 rpms with the flywheel rotating at 850 rpms.  In order to attain rev matching one blips the throttle to increase the engine rpms and releases the clutch pedal in such a way that the clutch disc and flywheel engage when the engine rpms and the clutch disc rpms are roughly equal.  This allows the clutch disc to seamlessly mate with the flywheel without any appreciable transfer of energy.

Contrary to the rule that all pedal inputs should be smooth, blipping the throttle requires that you “stab” the gas pedal. Your goal is to quickly increase engine rpms. As you blip the throttle with the clutch pedal depressed, stabbing the gas pedal does not upset the car. 

All corners were not created equal. Appropriate engine rpms for rev matching varies depending on the situation. You need higher engine revs when downshifting for a fast corner as compared to downshifting for a slow corner.

Determination of engine rpms while rev matching is done by listening to the motor.  With practice you will learn to listen to the motor and to be able to determine the optimal time to release the clutch after blipping the throttle.

If rev matching results in significant engine braking, then the engine was spinning too slowly when the clutch was released.  There are two possibilities.  One is that your blip did not sufficiently increase engine speed.  The other is that your blip was sufficient but you missed the “sweet spot”. You didn’t time the clutch release with peak engine rpms and clutch engagement occurred too late, after the engine rpms significantly decreased.  

If the car lurches forward when you release the clutch then you “over blipped” the throttle.  The engine rpms were too high when the clutch was released so that the engine drove the car forward.  The solution is to recognize, by listening, that you “over blipped” and wait an instant for the engine to slow before releasing the clutch.

Learning to rev match can be accomplished while driving on the street. The process involves the clutch pedal, stick, and throttle. The brake is not involved.  I don’t recommend learning rev matching when downshifting into second gear because second gear is too low. Practice rev matching when downshifting into third or fourth gear.

The exercise consists of driving in fourth gear and letting the car slow to an appropriate speed for third gear. Depress the clutch, move the stick, and blip the throttle. Listen to the engine and release the clutch quickly when engine rpms peak. At first you may want to keep your eye on the tachometer to learn to coordinate engine sound with rpms. Releasing the clutch at 4500 - 5000 rpms is usually optimal.  If clutch engagement was not smooth figure out why and make appropriate adjustments to your technique.  Repeat this until your downshifting is consistently seamless. 

TWO PEDAL ONE FOOT MANUVER

What works for me is to shift gears when the brake pedal is maximally depressed just prior to trailing off the brake pedal. Maintaining maximal brake pressure while blipping the throttle with your right foot is hard to do but can be learned. Trailing off the brake while blipping the throttle is much harder and may not be possible to do smoothly.

You want to wear your driving shoes when practicing the 2P1F because you want to simulate driving on the track.  The 2P1F exercise is performed with your car standing still.  Initially, practice with the engine off.  When you’re comfortable with your technique practice the exercise with the engine running.

To perform the exercise start with your right foot on the gas pedal, move your right foot as quickly as possible to the brake pedal making sure that the ball of your foot is centered on the brake pedal, put the brake pedal on the floor, and blip the gas pedal with your right foot.

For optimal engagement of the brake pedal you want the ball of your foot to be dead center on the brake pedal. You want the ball of your foot to exert all the pressure on the brake pedal.  You don’t want to use toes or the sole of your foot.

The reason for this is that when the ball of your foot is on the brake you will be able to use the large muscles of your leg and buttocks to create force on the pedal.  This maximizes your ability to slow the car.

With the brake pedal on the floor try to find the gas pedal with your right foot. Experiment with different techniques until you find the one that works the best for you. Some drivers like to roll their foot from the brake to the gas pedal. Some drivers use their right heel. Whatever technique you use you must maintain constant pressure on the brake pedal while blipping the throttle. It’s imperative that you engage the brake and gas pedals exactly the same way every time with your right foot. Practice until you can perform the 2P1F exercise consistently, smoothly, and quickly.

Now start the car, leave the car in neutral with the emergency brake engaged. Practice the technique listening to the engine and watching the tachometer.  You want to consistently be able to rev the engine to approximately 4500 rpms – 5000 rpms while keeping constant pressure on the brake pedal. 

Gas pedals are skinny. This makes 2P1F more difficult. There are a number of bolt-on aftermarket gas pedals that change the size and shape of the gas pedal in order to facilitate 2P1F. The disadvantage is that if you don’t center the ball of your right foot precisely on the middle of the brake pedal you may inadvertently engage the gas pedal while braking.

At this point you are ready to HTS at speed in the braking zone at the track. Not only will your downshifts be silky smooth, but your cornering technique will improve greatly as you will enter the corner with a balanced car, at an appropriate corner entry speed, in the right gear, and without distractions.