I pulled into Hide A Way Speedway one Sunday afternoon and just as I was going into the pits, a man came running over to me. I’m sure his name was Paul Delaire from Stratford, about twenty miles west. He told me his car would not handle properly and the tire pressure went up to 90 lbs psi. He said he kept letting air out but the psi kept going up. He told me that the pressure he started with was 25 lbs psi.
This was happening only on the right front tire. There was a creek or a small stream near the pit area. I told him to let all the air out and take the tire and wheel to the water and let them both cool down. Then, when cooled, to put 40 or 45 pounds of pressure in the tire. He looked at me as if I was crazy, but he did what I said, went back out to practice and the car handled better. When he came back in, the tire pressure was between the amounts that I said and the tire was not overly hot.
I had to sit down with him and explain what was happening. If you start with low tire pressure, the tire flexes and the flexing causes heat thus raising the tire pressure. Letting out air causes more flexing thus more heat, (remember, this was back in the 60s, things were different then). If you start with the proper pressure, there is less flexing, so less pressure build up, and the tire and wheel can do the job of getting the car around the corner.
Now, this was on a race car that only turned left, so, in those days the normal thing to do was to put a big, (larger) tire on the right front and a smaller one on the left front as the left one is usually in the air and only holds up the left front side of the car on the straightaways.
Years later, mechanics started moving the weight of the cars around making the left front tire do its share of the work. Now, this is mainly on paved tracks, the dirt track racers found that the old way worked best on dirt.
On the big tracks the tires are so important that they are set at the same tire pressure used there the previous year. By setting the pressure the same as they used before the team has a starting point to work from and can make adjustments accordingly. A little pressure up or down depending on the situation can gain a 10th or lose a 10th of a second very easily.
Courtesy of Jim Dunham
