Your front suspension must be complete and set for racetrack conditions before you can measure the bumpsteer. All components must be tight and in proper position, and you will need a quality bumpsteer gauge.
1. Set the car to ride height.
2. Use the proper size tires and air pressures.
3. Caster must be set.
4. Camber must be set.
5. Toe-in must be set.
6. Tie-rod lengths must be set.
7. Steering should be centered (tie-rod ends centered on inner pivot points lower ball joints).
8. Steering must be locked down.
9. Measure from the ground to the lower ball joint or other reliable reference point. Write it down.
10. Remove springs and disconnect sway bar.
11. Return the suspension to the proper height by using your reference number to the ground.
12. Obtain a supply of bumpsteer shims (washers).
13. Bolt on the bumpsteer plate to the hub. Level the plate and note where the dial indicator is on the bumpsteer plate so you can quickly return to the correct ride height.
14. Jack the suspension through 2 inches to 3 inches of both compression and rebound travel and write down your results.
15. Shim as needed.
* Source: Longacre Racing Products
On Street Stock suspensions, one usually must use stock-type ball joints and tie-rod ends. The location of these cannot be easily adjusted because they all have tapered shafts and fit in tapered holes. The bumpsteer on a stock automobile is normally quite accurate. Changes occur when we turn it into a race car. Chassis settings like ride height, radical caster/camber settings, and tall ball joints all affect the bumpsteer. This is the point where you should get concerned.
Bumpsteer effects will be more noticeable on paved tracks, less on dirt surfaces, and even less on small tracks.
In the absence of sophisticated measuring equipment, I have done the following to detect bumpsteer on a Street Stock. With the chassis on jackstands and the steering wheel locked, I held a carpenter's square against the brake rotor while the spindle was jacked up and down. If much bumpsteer is present, you will see the square move across the floor left or right.
On Original Equipment (OE) suspension-class cars there is little adjustment available to correct bumpsteer. Bending the steering arm of the spindle can often affect the needed correction. Another corrective action is to move the steering box. This can be a big chore. If this is done, the idler arm will need to be moved the same amount. Here I should mention many Street Stock-type cars still have the original idler arms. If the idler arm can be wiggled up and down, this will cause an even more erratic, intermittent, bumpsteer. In one extreme case, I lengthened the drag link to get rid of some bumpsteer.
Don't become too radical trying to get the last few thousandths of bumpsteer out of your Street Stock dirt track car; it doesn't make that much difference. But pay attention to it if you race on pavement. Do check it occasionally to make sure the steering arm of the spindle hasn't been bent. - Sleepy Gomez