By: Leroy Leese
Racers are constantly aware of the variables in racing. Throughout the day, many weather variables and mechanical items are changing. From week to week, even more things change. These variables must be checked, adjusted, and noted constantly. During eliminations, there are factors changing every round. You must take these into consideration before selecting your dial-in and your lane. Here is a short list:
- A headwind can slow the car by two- tenths of a second.
- Heat and humidity may require a jetting change.
- Ignition timing can vary over time due to worn parts.
- Valve lash also changes due to worn parts and requires occasional readjustment.
- A leaky pan seal may require additional transmission fluid if it goes unchecked, creating a trans slip or shift problem.
- Unheated engine, transmission, or slicks can slow the car by one-tenth of a second.
- Spark plugs eventually get fouled or widen their gap and need to be replaced or cleaned.
Characteristics of the rear tires such as tread loss, rubber hardness, side- wall deterioration, and air pressure changes (due to temperature of the tire) affect the slicks ability to maintain traction. If the slicks show a grain pattern, it’s time to reverse them. Many people compare tire pressures to see what works for other cars. This should not be done. Race cars using 4-link suspensions with a high and short instant center will hit the tire hard and therefore need more tire pressure than suspensions that use a long instant center. Sidewall construction can also affect the tire pressure requirement.