[jhv48]

Before you start chasing ball joints, steering rack, rotors, etc., for that 60-70 mph front end shimmy do the following: find a tire store that has the Hunter Elite Road Force Balancing machine. Then find an EXPERT that knows how to use it. Discount tire stores have the machines but rarely does anyone in the shop know how to really use it. Ask the manager if he has anyone that is an expert on the machine. If he balks, go to another shop till you find the guy that says he mounts and balances tires for race cars. Then watch him work. It’s a complicated procedure involving rotating the tire on the rim so that the high (Or thick spot) spot on the Tire corresponds to the low spot on the rim. Then the computer will tell him how to match the tire to the rim. Then it will spin the Tire and apply force to accurately cancel out any aberrations. The computer will tell him exactly where on the surface of the rim to place the weights. This procedure takes about 20 minutes per wheel so shops don’t like to do it unless you specifically ask for it. 99% of the tires they mount and balance use this same machine, but it’s only used to balance the tire. No more. And that will work on a 5000 pound SUV. But it won’t work on our light front ends.
The machine will also tell you the wheel and the tires individual runout. Rarely, you’ll get a tire or wheel that’s too far out of round for your application. Then you’ll have to get the sales shop to get another tire that is within specs.
Do this first before you do anything else. all of us with SPF’s have had this same problem.
I chased it for years, bought the new ball joints. Tightened the steering rack. Had the wheels and tires balanced on the car (that actually came closest). Checked tire pressure and alignment. Only after finding the EXPERT on the Hunter Road Force machine did I finally eliminate the shimmy.
It’s a common problem with a very specific solution.
Happy hunting.