Tech Talk Sprint Car Front End Squaring
Jason Martin, from Speedway Motors, demonstrates how to accurately square the sprint car front end. Follow along to ensure successful front axle squaring.
To start, put your front axle up on four-inch blocks, then make sure your chassis is level. Jason uses a three-foot level at the longest part of the chassis. Jack up the front until the frame is level. This makes it easy to set the caster later.
Once these steps are completed and the radius rods are loosened, you’re ready to get everything squared up. Now it’s time to measure the front axle. Using a wide tape measure, place it up against the back of the axle. Jason recommends setting it on top of the tire rod to prevent sliding. He also suggests keeping it in line with the front torsion arm to make sure you’re measuring from the same distance on both sides. These measurements vary depending on the chassis wheel base. A good measurement for an 88-inch car would be 47 1/4 inches. For an 87-inch car, the right measurement would be 46 1/4 inches and so on. Measuring this correctly guarantees an accurate right arm length. Jason says 13 ½ inches is the suggested spring rate typically used in sprint cars.
Now that the right-side measurements are correct, it’s time for the left side. These measurements depend on your personal preference. You can choose heads up, 1/8 inch back or 1/8 inch forward. This decision is affected by the type of track you’ll be on. This process will be very similar to what you’ve just done. Measure both sides and adjust the radius rod.
To set the caster right, use a sharpie to mark the top and bottom radius rod. This helps you rotate them in even increments. Set your angle finder on the top of the steering arm. 8-12 degrees is the suggested measurements. To adjust the radius rod for a higher degree, shorten the top radius rod and lengthen the bottom one.
Finally, you’ll need to set the side to side. Most people set their axle one inch to the left. Use your stagger tape to hook into the hole on the top of the kingpin. Look from the top of the frame to the bottom of the frame to get the measurement. Then, repeat the process on the other side. Jason recommends one inch longer on the left side than the right side.
Once the axle is square, radius rods are set for caster and the front axle is set from side to side, all you have to do is tighten everything else up. Thanks for tuning in!