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Terminology
 
This is what we send out to our guests after they have been confirmed for a driving event. Not everybody reads the stuff, but it is a chance to do some homework before school starts.
 
 
SPDT PERFORMANCE DRIVING TECHNOLOGIES
 

SIDOROV ADVANCED DRIVER TRAINING

THE LANGUAGE OF DRIVING

 

Every set of skills is likely to have its own terminology. In driving, we start with the concept of vehicle dynamics, or why motor vehicles do certain things. Even enthusiasts don’t always understand these terms, so we are providing a glossary for you to browse before your advanced driving course. It should also be a handy guide as you continue to develop your skills.

 

 CONTACT PATCH

 This is where the rubber meets the road, the part of the tread that is in contact with the road surface. It is actually a lot smaller than you might imagine.

 

LOAD TRANSFER

 At rest, a vehicle has the load, and therefore traction, fairly evenly distributed among the four contact patches of the tires. The variations are from the inherent front-rear weight distribution of the design. Use of any major control, such as steering, power, or brakes, transfers load, and therefore traction, among those four contact patches. Done deliberately this is a skill. Done inadvertently it can be a spin or crash.

 

SLIP ANGLE

 It is easiest to think of this in relation to the front wheels. Slip angle is the difference between where a tire is pointed, and where it is actually going. This is caused by the tire scuffing across the roads surface. Tire squeal occurs as the slip angle increases. When that angle becomes too great, the tire, and vehicle, starts to skid.

 

UNDERSTEER

 A condition in which the front tires have less traction than the rears, and begin to slide towards the outside of a corner. Also known as push or plough.

 

POWER UNDERSTEER

 This is caused by the driver beginning to accelerate too soon, too hard, or both, in a corner. The load transfers to the rear tires, giving them more traction, while the front tires, which are trying to turn the car, have less. The result is that the front of the car will start to run wide, since ability to steer is reduced. Hence, understeer.

 

OVERSTEER

 The back tires have lost traction. If it goes too far, the back of the car swings around beyond the driver’s ability to correct, resulting in a spin-out.

 

 TRAILING THROTTLE OVERSTEER (TTO)

 Oversteer caused by an abrupt release of the throttle, or gas pedal, while cornering. This transfers traction to the front tires at the expense of the rears. Unless corrected immediately, the result is a very rapid spin. This is a very common mistake among novice race drivers. Bear in mind that the troublemaker here is usually power understeer, followed by a panic response. Correct timing of throttle application, as well as learning how to squeeze the power on gradually, will reduce the chance of this sort of incident.

 

 THRESHOLD BRAKING

 A tire stops best when it is held just before the point of lock-up. This means that the wheels will be turning at slightly less than vehicle speed. Good anti-lock brake systems manage to do this. A skilled driver can do the same, by rapidly engaging the brakes to the threshold level, then maintaining this level through gentle modulation of the pressure as the vehicle slows.

 

 TRAIL BRAKING

 Slow to medium speed corners are often best handled by carrying some brake pressure past the turn-in point. The driver goes from a high brake level in a straight line, then begins gradually easing off the brake (trailing), while beginning to add steering input, so one force balances out against the other.

 

FEEDING THE WHEEL

 Also known as shuffle steering or push-pull. A more accurate and less dramatic form of steering than hand-over-hand, and much safer than any one-handed window washer technique.

For a left turn, the hand on that side moves to the top and pulls the wheel a full half turn to the bottom. The right hand stays in contact with the wheel, sliding down to meet the left hand at the bottom. The right hand then pushes up on the wheel, while the left hand mirrors the movement until both hands meet at the top. Continue as needed. 
 
Smaller "shuffles" can be used so that in cornering, the hands remain at about 9 and 3.
 
In airbag-equipped vehicles, try using the bottom two-thirds of the wheel for this manoeuvre. That will reduce the chance of a 200 kph punch in the head should the airbag deploy.

 

HEEL-&-TOE DOWNSHIFTING

 A technique in which the engine revs are raised during downshifts to permit the gears to engage more smoothly. This is done while maintaining brake pressure at a constant level. The uprev or “blip” occurs after the clutch is depressed and while the shift lever is being moved to a lower gear. Modern sequential semi-automatic gearboxes often do this for the driver.

 

CORNERING TERMS

 Turn-in point. This is where the driver starts to turn the wheel and initiates the cornering sequence. It should be deliberately chosen, not a random act.

 

Clipping point or apex. The point where the car is closest to the inside of the corner. A late apex is desirable in most cases. Getting to the inside of the bend too soon, an early apex, is likely a sign of early or abrupt turn-in and can cause problems later in the corner.

 

Track-out or exit. The turn is finished, the lateral forces are done.

 

That should do it. All of this and more will be covered in the vehicle dynamics session. We look forward to seeing you at our driving event.
 

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