What's the worst that could happen if your driver keeps crutching the race car? Well, the
• The front springs are too stiff. This makes the car tight by not allowing the front suspension to roll and work with the rear. You want both the front and rear of the car to pivot around the roll centers in unison, or the car binds up and is tight.
• The Panhard bar is set too low. If the bar is mounted too low for the springs you have chosen to run, the rear of the car will roll more than the front, making the car tight.
• The front roll center (RC) is too far to the right or left of the centerline of the race car. If the front RC is too far left, the car will roll excessively in the front and the right front camber will change too rapidly, causing a loss of grip in the tire. If the RC is too far right, the front end will not want to roll and if the rear rolls free, the car will bind up, much the same as having springs in the front that are too stiff.
• The crossweight percentage (right front + left rear) is too high. Crossweight is the weight on the right front and left rear tires. Too much of it will cause a car to be tight as the right front gets overworked.
• Using excessive Ackermann angle in the steering system. Some racers have steering systems that create too much Ackermann angle gain (one wheel steers more than the other to account for the different radii they experience), which causes the car to have too much toe-in or toe-out in the middle of the turn. This will cause the front end to skate and push, which makes the car feel tight.
Notice the angle these dirt cars are negotiating in the corner. They are hardly sliding ou
• Running with too little stagger in the rear tires. Insufficient rear-tire stagger will cause the car to "point" toward the outside wall upon exit. There is a correct amount of rear stagger for each track based on tire diameter versus the radius of the track versus the track banking angle. Also, too little stagger usually will drive the car to the right in the middle of the turn.
Get Ready for More
This is probably more information than you can process, but we're just getting started. Look for the next race car crutches installment next month and get ready to learn more about why you're not going faster.
Is There a Difference in Dirt vs. Pavement Chassis Setup?
For years, chassis setup for circle track cars has been accepted as being different for pavement and dirt track cars. But we've discovered that the same theories and setups are common across the board.
Bob Bolles (right) confers with dirt Super Late-Model ace Kevin Weaver at Eldora Speedway.
So, you ask, how can that be if dirt cars slide the rear end out entering the corner? According to one of the top drivers in the ever-competitive Hav-A-Tampa Super Late-Model dirt car series, "sliding a dirt car into the corner is to help the car turn in, but sliding your car sideways in every corner is not the fast way around the track. For quicker lap times, we are constantly working on the suspension, steering, and chassis to get the car to turn in with less angle in the slide of the rear end. Sliding the rear scrubs off speed and uses the power of the vehicle to negotiate the turn instead of pushing the car forward. As racers all continue to learn more about chassis setup and the like, you are going to see less angle in the power slides into the corners. This is because racers are figuring out how to set up dirt cars to drive around the track, instead of slide around-and driving is quicker than sliding.
Crutches to Watch for in the Future
Plenty of crutches are being employed by racers every day, so this series of technical articles exposing these crutches is going to go on for many months. Look for stories on crutches such as extreme right front camber, excessive stagger, rear steer to the right, spring mounting location on the chassis, shock absorber misuse, excessive toe settings, too-stiff right front spring, longer right-side wheelbase, and out-of-proportion corner weights, among others. This list could be longer, but these are some of the most common crutches and will keep all of us busy. We plan to support these articles with documentation from real track testing of these theories to show how they work in the real world of racing.