cobra valley ball joints

[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.

[NRP/MN]

While Jim is 100% correct on his solution, I have been encouraging my customers to upgrade to the friction free ball joints. I just upgraded a Unique for a customer. Factory ball joints are bound up ridiculously tight and in effect add spring rate and reduced movement in the front suspension. You only need to remove the front wheels to do this. A ball joint spreader is the key. The original ball joints are 772 Chrysler screw in. It helps to have a socket for the ball joint.

[Hall1836]

nk you.

[Hall1836]

Thanks to those that responded. When I first got the car last year it had sat for several years with little or no use. I changed fluids and greased where necessary. After greasing the ball joints I noticed that the shimmy was reduced but over time returned. New tires mounted by a friend who trust. Mounted tires on the car and it felt like the shimmy improved. Yesterday, I decided to adjust the rack free play. After raising the car with the suspension fully extended, I made a jig to check the tires for run out, and adjusted the rack. I took the car for a ride and the shimmy was reduced. I thought the rack adjustment had done that. However, the longer I drove the shimmy got a little worse. My thinking elevating the car freed the suspension. I made some agressive left and rights and the shimmy was reduced but returned as I drove. I'll probably try the new ball joints and will post results. Thanks