Check Out That Chassis

By Jim Salemi
7/12/04

Jim, I have a backhalved 1968 Mustang, which is primarily a street car. I have noticed a driver’s side sag, so I decided to readjust the 4-link. I removed lower bars and set them both to 23 inches for the correct wheelbase. I then set the upper driver’s bar to pinion angle one to two degrees below shaft. All of that went fine, but the fourth bar is giving me problems. The axle just doesn’t appear to be centered in the wheelhouse. Should the tires be removed when setting up? Can the car be on jack stands? Does the rear end need to be at ride height when setting up? Anything you can tell me may help. Thanks, Aaron

Aaron, Thanks for the questions and reading DRO. Your process is decent in what you are trying to accomplish. I offer these other suggestions to possibly get you a little closer. What you first would want to do is make sure the rear end is square to the car itself. There

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are of course many ways to accomplish this task. An easy way is to find the center points of the front and rear of the frame and place a string over the points so that you have a point of reference for measuring. Also find the center of the rear end housing and then make sure that they are all in line with each other. That will assure you the car is tracking
properly. Another good check for this is to extend the sidewalls of the rear tires forward to the front of the car. You can do this by running string or using something that is long enough to extend to the front of the car. Take measurements to the frame or another fixed point that should be the same side to side. You should be within a quarter to half of an inch side to side. A car that is not square to itself will be inches of by the time it is extended to the front. The car needs to be at ride height when performing these tasks. Possibly you should look into having new 4-link bars made to insure that they are proper in all ways. As far as the problem with axle housing not being in the
center of the wheelhouse, when parts aren't welded in fixtures the tend to move around from original status. Adjustments need to be made to compensate for looks but not overall performance.

To contact Jim Salemi write chassis@dragracingonline.com