Many Austin-Healey owners complain of a common problem - that of front end shimmy or vibration at speed. Generally, this problem is the result of excess wear of some or all of the various components making up the front suspension, especially if these parts have not been rebuilt for some time. It is fairly easy to check for many of the wear problems, and I've listed some methods which can be utilized.
To check for wear in the kingpins:
Jack up the front end of the car and support it so the wheels run free. Grab the tire at the bottom and attempt to move it in and out. Look at the kingpin bushing locations (especially the bottom one) and see if there is any movement. If there is noticeable play, the kingpins should be rebushed and replaced. A grease job will help here, but only temporarily.
To check the ball joints:
Grab the tie rod ends at the ball joints and attempt to move them back and forth. They should feel tight and difficult to twist. If they feel sloppy and loose, they are probably worn out. Early cars require greasing of these joints. Some very early cars have adjustable ball joints to compensate for wear, but these cars are rare. Often, greasing has been neglected, resulting in excess wear. Later cars, such as BJ8s, do not have grease fittings and the joints are sealed and lubricated for the life of the part.
To check wheel bearings:
Grab the wheel at the top and bottom, and push and pull to determine if the wheel will move in or out at the hub. If there is noticeable movement here, it indicates that the bearings are loose, and in need of adjustment with shims. It could also indicate that the bearings are badly worn. To determine if they are worn, the hub must be removed and the bearings and races inspected for pitting, scoring, cracking, or other wear marks. If a situation such as the above exists, the bearing must be replaced and properly adjusted.
Excess movement in the steering box can be determined by turning the steering wheel slowly and checking how much play there is before the front wheels begin to turn. Over an inch of play generally indicates wear of the steering box. Another check is to push up and down on the bottom of the steering shaft below the box. There should be very little up and down movement. Much of the looseness and wear in the steering box can be adjusted out by various means. On earlier cars, such as the 100s, adjustment usually means removal of shims under the steering box cover. Shims are also provided at the front bearing plate of the box. On later cars an adjustment mechanism is provided in the form of a locking nut at the top of the box. If adjustment does not get rid of excess movement, the only alternative is a rebuild of the steering unit.
Front shock mounting locations:
The front shocks should be checked on a regular basis, as loose front shocks can lead to very dangerous situations (read "wheel collapse"). All four bolts on each shock attachment point must be checked for tightness and, if loose, torqued down accordingly. If the bolts will not tighten, check that the threads in the shock tower have not become stripped. If this is the case, the top plate may have to be replaced (a very costly and difficult chore). Loose shocks can lead to bad front end vibration (as experienced by a club member recently on a long distance trip).
Tires and wheels:
If all the above tests are satisfactory, then the vibration problem is most likely in the tires or wheels. If the wheels are old with loose spokes and bent rims, they should be rebuilt or replaced with new wheels, which are readily available. If the wheels and tires are fairly new or in good condition, balancing by a reputable tire shop is recommended. This will generally solve the problem.
Remedying the above possible defects should solve any front end problems. If the car still vibrates, it is probably caused by frame or front end accident damage. These components can be very difficult and expensive to repair, but the job is not beyond the ability of a good restoration shop.
Check Front Suspension for Wear