With more angle of attack,...
With more angle of attack, the front and gains more traction up to a point at which the angle becomes excessive and the tire loses grip and gives up most of its available traction, resulting in a severe tire push.
A track that has a decreasing radius in the latter portion of one of the turns can cause a car to develop a loose condition at that point. Some older dirt tracks and ones that were originally dirt and then paved retain a straight front stretch and a rounded-out back straightaway. This D shape causes Turns 1 and 4 to have a smaller radius than Turns 2 and 3. So its difficult to accelerate off Turn 4 due to the slower speeds caused by the decreasing radius.
Remember, we said traction increases for a set of opposing tires when we increase the angle of attack (simply put, this is when we turn the steering wheel more). If the car is neutral in and through the middle of the turns, as we approach the tightest portion of the turn past midway, where the radius is less, we need to turn the steering wheel more; that produces more front traction than rear traction. The balance we enjoyed through the middle of the turn is now upset and the car becomes loose just when we are getting back into the throttle. This causes loss of rear traction. We will study ways to compensate for this later.
We see one car can run the...
We see one car can run the very bottom of the racetrack while the No. 1 car runs high. When the side bite is there the shortest way around the track is on the bottom. If we also have forward bite, we can accelerate off the corner sooner and with a more straight-ahead line.
The Racing Surface The surface we race on largely determines the amount of traction available under power, and we will look at dirt and asphalt tracks separately. On dirt tracks, the amount of moisture dictates the amount of grip the track gives us. Bumps, grooves, banking angles, and the turn radii all help determine how much grip is available for traction off the corners. The setup related to shocks, springs, and rear geometry help determine how much traction will be available for a certain set of conditions.
On asphalt tracks, and even some dirt tracks that have been oiled to the point of almost being asphalt, the surface is more consistent. Other than holes or bumps and rises in the surface, we can expect the grip to be the same over the course of the entire event. Flatter banking and older asphalt dictates the need for more traction control efforts.
Now that we have a good understanding of exactly what affects the amount of traction in our tires, we need to examine how we can use that information to enhance the tractive properties of all four tires. In Part Two of "Get More Bite," we will offer some suggestions for overcoming the problems some teams have getting enough lateral and forward bite.
Many current dirt tracks,...
Many current dirt tracks, as well as some asphalt tracks that used to be dirt, have developed a D shape. This is caused by having a wall along the grandstand side only and, as the track gets raced on and groomed, the back side away from the grandstand gets pushed out. This makes Turns 1 and 4 tighter than Turns 2 and 3. More steering is required for the tighter turns, and it is usually very difficult to accelerate off the corner in Turn 4 as opposed to exiting Turn 2.
There is one traction-promoting effect that every stock car has, but few realize. It is the effect of engine torque. When we get back into the throttle, the torque from the rotation of the engine, through the driveshaft, tries to rotate the whole rear end in a counter clockwise direction when viewed from the rear. This action, or force, loads the left-rear tire as well as the right front. When those two corners are more loaded, the crossweight percent goes up and the car gets tighter. Also, if the RR tire was supporting more weight than the LR tire, then with this effect, the two rear tires would be more equally loaded, providing more forward traction.
A question often asked is, "why doesn't the car get loose immediately when we gas it up if the rear tires are already providing all of their available traction, keeping the car off the wall?" The introduction of power would cause the tires to lose traction if it were not for the added effect of the engine torque. There is no way to enhance this effect, and the magnitude is entirely dependent on the amount of torque the engine develops at a given rpm versus the track width of the rear tires. The wider the rear track width, the less effect torque will have on adding to the LR weight.