Some tracks and sanctioning...
Some tracks and sanctioning bodies allow the use of tire treatment whichsoftens the rubber compound. This can be a way to limit cost, allowing ateam to run otherwise uncompetitive, hard, old tires. Other tracks lookthe other way on this issue and the teams must soak their tires in orderto be competitive. Promoters should define and enforce tire rules eitherway.
Camber also affects the size and cross-sectional loading of the contactpatch. The correct camber angle compensates for the deflection of thetire sidewalls as the lateral force is applied when we turn the car.More or less camber than ideal means one side of the tire will supportmore weight than the other, which also reduces traction.
3. Chemical Makeup--The chemical makeup of the compound of therubber will help to determine how much traction is available from atire. A softer tire will provide more traction, but the maximum amountof traction that can be utilized over a long period of time depends onhow the tire holds up to heat and wear. A tire that is a little hardermay sometimes hold up better and be faster towards the end of the racewhen the tires have built up a lot of heat and are well worn after anumber of laps.
(above & below) If we could...
(above & below) If we could look down on the tire contact patch during cornering, wewould want to see an even pattern across the width of the tire, muchlike the sketch on the left. If the right rear tire had too muchnegative camber set into it, at mid-turn, the contact patch might welllook like the pattern on the right and the tire would have lesstraction.
4. Angle of Attack--The amount of traction available from a tirecan actually be enhanced simply by increasing its angle of attackrelative to the direction of the car, but only up to a point. Fromstraight ahead, we can turn the wheel and, with each degree of angle ofdeviation from the direction of travel, the traction in the tireincreases. There is a point we reach where the gain is reduced and weapproach the limit of attack angle that the tire can handle. Once thatpoint is reached, going beyond causes a sudden loss of grip and tractionfalls off drastically. This principle is true of all four tires whetherfront or rear. We will provide more on this subject later.
5. Equal Loading--An opposing pair of tires (tires on the sameaxle at the same end of the car) will develop maximum traction when theyare equally loaded. That is a generally true statement, but upon morecareful examination of how we do things in circle track racing, there isa unique situation where that is not exactly true.
The situation is when we have a tire on one side of the car (usually theleft side) that is built with a softer compound than the opposing tirewhereby it may be able to develop more grip under the same loading asthe opposing tire. So, increasing the vertical load on the inside tirewith the goal of attaining equal loading for both tires, by whatevermeans, may not actually generate more traction because of the differencein grip per pound of vertical loading created by differences incompounds.
The shape of the track for both dirt and asphalt can influence theavailable traction in several different ways. As we apply power, we needto know a little about how the track is banked, how the banking angle ischanging coming off the corners, and how the radius of the turn might bechanging. A highly-banked racetrack is very forgiving when it comes toneeding bite off the corners. There is so much downforce due to thebanking and associated lateral forces, that many times the tires areloaded to the extent that the available amount of horsepower cannotbreak the tires loose under normal conditions with a balanced setup. Thetracks we often worry about getting off the corners are the ones thatare flatter and with less surface grip.
Many current dirt tracks,...
Many current dirt tracks, as well as some asphalt tracks that used to bedirt, have developed a "D" shape. This is caused by having a wall alongthe grandstand side only. As the track gets raced on and groomed, theback side away from the grandstands gets pushed out. This makes Turns 1and 4 tighter than Turns 2 and 3. More steering is required for thetighter turns and in Turn 4 it is usually very difficult to get tractionunder power, as opposed to exiting Turn 2.
The severity of change in banking angle of the racing surface in theportion of the track where we are initially accelerating can causechanges to the pitch angle of the chassis that works to unload one ormore tires, reducing traction. A track that goes from high banking tolow banking fairly quickly can cause the left rear tire to unloadquickly, making the car loose.
There are two ways this can happen. One is when the outside edge of thetrack drops in elevation and the right front tire follows the drop-off.This lifts weight off the left rear tire, causing loss of traction inthat tire.
The other problem occurs when the inside edge of the track rises up tomatch the elevation of the outside edge of the track. As the left fronttire rises up, the left front and right rear pair of tires become moreloaded, momentarily causing loss of loading in the opposing pair oftires. The loss of crossweight percent (right front to left rear) makesthe car lose traction in the rear.
A track that has a decreasing radius in the latter portion of one of theturns can cause a car to develop a loose condition at that point.Usually, older tracks that were originally dirt and then paved retain astraight front stretch and a rounded out back "straightaway". This "D"shape causes Turns 1 and 4 to be a smaller radius than Turns 2 and 3 forthat reason. So, it is difficult to accelerate from Turn 4 because ofthe decreasing radius.