Dirt Race Car Handling Problems; Diagnosing and Fixing

How to evaluate race car handling problems

I think it is as important to develop a process to think about solving dirt race car handling  problems as it is to actually come up with the solution. I don’t know how many times a problem is diagnosed at the track and a quick solution is thrown at the car, only for it to be the wrong solution. On the ride home we think about the problem more thoroughly and come up with a completely different solution that works better the next week. After struggling with situations like these throughout the years, I have come up with a method of thinking about problems and coming up with solutions that work better in pressure situations at the track. The first thing that I must say is that I don’t believe in a certain “set up” or the cliché thinking of: if the car is loose, do this, or if the car is tight, do that. Well tuned race cars are not that simple.

Everything revolves around the driver

I need to start the description of my process with the statement that tuning a car revolves around a driver. The best thing you can do is make the driver comfortable and confident in the car. It is getting more important that a driver drive the cars a certain way. Now I don’t mean that all drivers will have the same driving style, but the days are gone that a driver can get away with slamming the brakes and pitching it sideways into the corner, and still be fast.

Which leads me to the first way to diagnose a problem. If you do have to shut the right front brake off to turn the car on entry, your car is too tight. This is one of the most basic tell tale signs as to what may be going on with the car. If a driver tells you the car is loose and he is running with the right front shut off or he has excessive rear brake in the car, the car is too tight. I’ve had drivers tell me they never turn their right front on or that they always run their brakes biased to the rear.  I know many drivers who get this to work, but there needs to be a cushion or some bite on entry to catch the car as it starts to rotate, and someone who has a car that turns well will drive by you as you wait for your car to turn or stop sliding. Concentrate on getting your car to turn on entry.

Car too tight in the middle?

The second thing I have learned to look for now is the off the gas time delay in the middle of the corner. This may take some experience to pick up on, but my rule of thumb is that if a car is too tight in the middle of the corner the driver will have to wait longer off the gas for the car to rotate. If the driver picks up the gas on a tight car it will push across the center unless he lets it rotate further before picking up the gas. Most cases I see where a car is slow through the middle it is way too tight on the gas. This could be solved several ways, depending on several other factors, but taking out dynamic wedge, adding a little roll steer, or decreasing panhard bar incline angle are some of my go to adjustments for this.  It sounds simple, and not always true, but off the gas is slow. If your car will rotate on the gas, driving the car on the fastest line on the track, your lap times will improve.

Where does the driver lift?

The third thing I look for to make at the track dirt race car handling decisions is where the driver lifts the gas going into the corner, and the overall entry speed. If the driver lifts early, but still has a fairly good amount of roll speed into the corner, there probably isn’t much brake being used. Tuning with anti-dive probably won’t be too affective, but softening or stiffening the right front spring to adjust how hard the car hits the right rear spring will probably have a profound effect. To the same effect watch the car attitude going into the corner. If the car noses down and tails up, it is a good indication that a fair amount of brake is being used. Tuning with anti-dive will be very effective along with tuning with the left front spring. A driver that starts his rotation into the corner on the gas will feel the right front spring rate effect handling much more than a driver that brakes heavy going into the corner. Different ways of entering the corner will require different fixes when a driver comes in and generically says the car is loose on entry.

This is the most common problem when drivers discuss car setup between each other. They leave out comments on how they drive the car and just tell each other what they did to fix it. The crew needs to know the drivers driving style and identify that look in the car in order to make corrections to the setup as the night go on. I think this happens to be some of the karma between driver and crew chief they talk about on TV. all the time. The crew chief understands the driver through car attitude, pitch, roll and speed and can make handling adjustments quickly and precisely.

Til next time, race hard,

Kevin

Comments

  1. Steve Campbell says

    My daughter drives a minimodified at Clarksville speedway 1/8 mile mild banked clay dirt track. When we hot lap and In the heat race the car is hooked up great but when it comes feature time the track slicks up and she gets a bad push when getting back on the throttle its pushes up the track then she gets lose off what kind of adjustment should I be making

    • Kevin says

      It sounds like there is a lot of wedge in the car. I’m not really familiar with the mini modified rules, but it sounds like the left rear tire is too dominate when the gas is reapplied after the apex of the corner. After the car pushes up she has to flare the gas to get it to turn … then it’s broken loose on exit. I would try to take some static wedge out of the car or some dynamic wedge by softening up the right front spring.

      Thanks for visiting the site.

      Kevin

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