Fortunately, there are only a very few things that can cause this problem:
1) Wheels out of balance (which you have already found to be okay). 2)
Front end alignment (the most likely cause for the problem). 3) Loose or
severely worn kingpins or other front end components. I would be willing to
bet that if you have the front end aligned, the problem will go away.
From: Greg Mahney <firstname.lastname@example.org>
To: email@example.com <firstname.lastname@example.org>
Date: Tuesday, August 10, 1999 5:17 AM
Subject: Shaking Steering
>Would any one care to offer a diagnosis on the basis of this info... (or at
>least a priority order for checking things).
>Every time aI drive my 1963 sprite and reach certain specific speeds eg 24
>mph, 46 mph, I feel a stong vibration through the steering wheel, like I've
>run over a particularly rough bit of road. When I'm not at those speeds it
>I'm sure it isn't wheel balance, as I've had them recently balanced and the
>rears and fronts swapped, and the symptoms are identical. The rest of the
>suspension is anyone's guess - I've certainly never touched it.