Even if your wheels are properly balanced - statically and dynamically with weights on both sides - and the machine reads zero-zero on the check spin there is always a slight residual static and dynamic unbalance because modern machines only balance to within about 2-3 in.-oz.

I KNEW my steering damper was leaking, but I put it off, and the car on a couple of occasions went into the worst front end shimmy I have ever experienced, and the wheels were in good balance. Shame on me. That steering damper (not dampener or dampner) is there for a reason and an IFS with a lot of caster needs one.

If the damper is leaking, it needs to be replaced ASAP. It's also easy to disconnect one end and test it. Gas pressure should expand it and it should take a good 20 pounds of force to slowly compress it.

If it's leaking or limp - REPLACE IT!

Duke