Be sure to check out the video highlights of our test at the end of the story!

Testing is extremely important. Anytime we conduct a test, be it at the track or on a dyno, two things come to mind. One is a tech column Bob Bolles wrote a while ago about all of us being scientists. Testing in an effort to find a result (favorable or unfavorable) yields useful information that we use, regardless of if it’s positive or negative. The other is something I heard at AETC, which is “you either have data, or you have an opinion.” Much of our testing starts from an opinion or a logical theory, then through testing the desired outcome is either validated or disproved, which is how this story came to be.

Bob wanted to test a pull bar on Dick Anderson’s Mustang Super Late Model to see how rear steer would affect the car exiting the corners. The original theory was that letting the rear differential rotate under acceleration when the trailing arms are mounted at different heights would create rear steer to the left, allowing the car to have more bite off the corner. Another benefit of this should be a much more stable feeling for the driver, as the rear of the car should stay square instead of drifting towards the wall exiting the corner.

To test this, we headed to Desoto Super Speedway in Bradenton, FL on two separate occasions to test two different pull bars—one formally sold by Allstar Performance and one currently availablefrom Coleman Racing Products. The Desoto 1/3-mile oval sports 14- to 16-degrees of banking and is a pretty fast and rough track. In our last test with Dick, the car was run at Orlando Speed World, which is a much flatter track (about 6 degrees). The setup for the flatter track will make the car tight on the higher banked surface. To alleviate this, the Panhard bar was raised to make the car neutral.

After some baseline laps, the solid third link came out and the Allstar Performance pull bar went in. This bar has a 1,600-pound spring and an internal hydraulic piston with a remote canister to adjust the preload of the spring. The bar was installed with the adjustment set to full loose. Our Replay XD camera was pointed at the bar when Dick headed back out on track, and the pull bar instantly went to work. The bar moved about 3/4-inch and let the rearend rotate about 4 degrees, which equates to an 1/8-inch of rear steer.

“The car felt pretty good with the solid link, “ explained Dick Anderson. “We put the Allstar pull bar on the car and I could feel an improvement. It snugged the car up, which it needed at that track.”

After analyzing some of the video from the day of testing, we wanted to make a few changes to see how the car would react, and we started with the bump springs. The car runs 1,200-pound bump springs. In an attempt to see what they are doing on track, we put one of our Replay XD cameras under the hood pointed at the base of the shock. We were surprised at what we found. The 1,200-pound spring came very close to coil-bind. The issue was remedied by swapping the 1,200 pounders for 1,500-pound springs, which reduced the amount of travel in the bump spring. Travel is camber change and we want to limit that while still providing compliance (movement of the suspension over the bumps). Dick didn’t notice the difference between the two on the track, but less travel without being close to coil-bind is a more favorable setup. A second video verified the change worked, and you can see both videos at