Eliminating binding in A-arms and racks

National Dragster, Oct 17, 2003 by Jones, Rick

Over the course of this race season, I have noticed a lot of race cars that have developed binds in the front suspension, specifically bindine in the A-arms and the rack-and-pinion. This binding can spell trouble for any racer. Not only can binding in the front suspension cause a loss of performance through a loss in weight transfer, but it can lead to the failure of suspension components, which can be extremely dangerous.

Any component binding will cause an overall loss in performance that can be hard to track down and may leave a racer chasing his tail! In this installment of Chassis Chatter, I'm going to concentrate on reducing the possibility of binding and, I hope, help racers to eliminate front-suspension binding in the steering by reviewing the proper installation of the A-arms and the rack-and-pinion.

First, determine whether the car has any bind in the front suspension by removing the front springs and running the front suspension through its entire travel. Check for bind in every section of the front suspension, including all rod ends. Fix any binding as soon as possible, ideally before the car is taken to the track again.

Mounting a rack in a race car can be a complicated, time-consuming process, but if one takes the time and care to do it right, the benefits will show in maximum performance. First and foremost, the rack needs to be mounted in a place that will give the correct geometry for the car's front suspension. The mounting height of the rack, top and bottom, is dependent on how the tie rods attach to the steering rod on the spindle or strut. If the car is set up with A-arms, you need to visualize an imaginary line from the centerline of the lower-control-arm mounting on the inside (rod end or bushing) and the centerline of the ball joint. Keep the tie rod of the rack-and-pinion mounted at the same angle of that imaginary line; i.e. if the bottom control arm is mounted at 5 degrees up on the outside, the tie rod should be mounted at 5 degrees up. It is very important to have some shims between the rod end and the steering arm so that when toe change is set, you will be able to adjust the rod end on the rack tie rod up or down.

Make sure that your rack-and-pinion is centered left to right in the car. To do this, first rotate the pinion in one direction until it stops. Turn the pinion in the opposite direction, counting the number of turns as you do, until it stops. Turn the pinion back in the other direction until you get to the middle of the rack's range. With the pinion set at the center of its range, position the rack-and-pinion in the car, measuring off both ends of the rack, and center the rack in the car.

If you mock up your rack and your front suspension, with the spindle set at ride height, you need to run the front suspension through its travel and check the toe change. As the front suspension runs through its travel, note how much the toe changes and shim the tie rod up or down (or move the rack itself up or down) to keep the amount of toe change to a minimum. It is always best to have no toe change. Minor toe-in can be acceptable, but toe-out should never be allowed!

Most rack-and-pinions purchased will already be assembled and have an established width. By this I mean the pivoting of the tie-rod ball joint on the end of the rack. Ideally, the tie rod needs to be the same length or slightly longer than the length of the lower-control-arm pivot points. If it is shorter, it will travel through its arc quicker and cause more toe change. A longer tie rod will only help you. As a general rule, get your rack as narrow as possible and your tie rods as long as possible to help keep toe change to a minimum.

By looking from the top of the car, you can determine where to mount the rack front to back by drawing a line across the car from where the tie rods attach to the steering arms. Never mount the rack behind this point. I recommend having the centerline of the rack-and-pinion mounted between two and three inches forward of this line. Any more than three inches can lead to binding problems when the car turns one way or the other. Once the mounting locations for the rack-and-pinion have been determined, mock up the rack and turn the wheels all the way to each side. Make sure that the tie rods are not binding at the balljoint area on the inside of the rack. To do this, turn the wheel all the way to one side, disconnect the tie rod from the steering arm, and make sure that there is still room for tie-rod movement. If there is no room for movement, adjust the rack-mounting location so that there is enough clearance for tie-rod movement. Otherwise, you risk damage and even failure at high speeds.

Having A-arms and the rack-and-pinion mounted correctly will help keep the chances of bind in the car's front suspension low, but there are other areas of the front suspension in which binding can occur. I'll discuss those in the next Chassis Chatter.

Rick Jones owns RJ Race Cars Inc. and Quarter-Max Chassis & Racing Components in Galesburg, Ill. RJ Race Cars has been building doorslammers since 1987 and was named the Car Craft Chassis Builder of the Year in 1998 and 2002. Quarter-Max Chassis & Racing Components is Jones' mail-order division which offers high-quality components for Pro and Sportsman racers. Jones has published a chassis-tuning guide that is available through his mail-order company. Readers can send their questions or comments for Rick Jones via e-mail to ChassisChatter@rjracecars.com or via fax to (309) 343-0886.