Page 18 - PCA Metro NY Region POST | 2019-April-eMag
P. 18

Basic Basics
This article is an at- tempt to begin at the beginning of explaining the underlying prin- ciples of track driving. It won’t hurt advanced drivers to read it, but
it is intended for the track novice.
First of all, some points I’ve made in other articles which are important for nov-
ices to understand:
• Your Porsche is ready to hit the track if it has been properly maintained. It does not need any special modifications at all. It is ready to go. • You must have a ‘Snell approved’ SA or M 2010 or 2015 helmet. Metro has a supply of loaner helmets for members who don’t yet own their own.
• There will always be a trained instructor with a 2-way communicator in your car with you when you are on the track,
There are three fundamentals which govern how fast a given car can get around a track, and they are grip, the path that the car is on, referred to as the vehicle’s line, and vehicle dynamics.
Grip is the amount of traction the tires can pro- vide in combination with the road surface. Dif- ferent tires have different maximum amounts of grip. A high-performance tire has much more grip than a snow tires does, as example. Addition- ally, dry pavement provides more grip than wet pavement, and much more than icy pavement. Changing the pressure of the air in the tire will also influence the available grip.
The amount of grip available at any moment has influence on the maximum speed the car can sustain in a corner and how effectively it
can slow down. The numerical measure of this amount is usually expressed as a fraction of the force of gravity. An ordinary tire can corner at about .8g, where the ‘g’ is the gravity force. A performance tire can corner at about 1.1g, and a track tire at about 1.3g – all those figures are on warm dry pavement.
The line is the path that the car is travelling. We all have an intuitive understanding that we must slow down more for a sharp turn than for a gen- tle one, but likely we haven’t explored why that
is so. The reason is that the forces at a given speed in a turn are, in physics terms, ‘inversely proportional’ to the radius of the turn. This means that if you halve the radius of the turn and keep the speed constant, you have doubled the force on the tire; but the tire can only sustain its maxi- mum force. When it is subjected to more force than that amount, it starts to lose its grip on the road and begins to slide across the pavement, which might lead to a spinout. That is why we must slow down more for a sharp turn than for a gentle one.
So, what we want to do when we’re driving on the track is to make each corner as ‘gentle’ as possible. But how do we do that, since the cor- ners are laid out on the pavement in asphalt and we can’t change them? The answer is that we don’t stay in our lane, as we do on regular driv- ing. Rather, in a right-hand turn, we approach the corner by hugging the left side of the road. We then put the car (at the “turn-in point”) on a path to make a smooth arc touching the inside (right side) of the of the road (the “apex”) at the half- way point of the turn, and we guide the car back to the left side of the road (the “track-out point”) at the end of the turn.
(Continued on page 18)
Track Ramblings

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