There are several posts regarding tire balance problems. Most fixes, or near fixes, indicate the Hunter 9700 Roadforce balancer is the way to go. The reason for this is that the machine also actually places a side load on the tire. Simply put, this loading (road force) simulates side forces on the tire walls that are generated as the tire wall flexes outward and inward in response to the perpedicular force applied along the tire contact patch area, as that particular area of the tread contacts the pavement. This flexing can contribute to a suspect tire/wheel imbalance problem even though the tire and wheel are "true".

There have been other posts that indicate the Hunter does not cure the problem, no matter what type or quality of tire is installed. We have heard other comments regarding the relatively low mass of the aluminum suspension system as a contributing factor. This low mass makes it even more important to get the tires "balanced" correctly, because the low mass components make it easier for any tire/wheel vibration to reach the drivers hands, feet and butt.

I'd like to add to what'* already been said here by my neighbor.

The sidewalls of the tire flex under the weight of the car as the tire rolls. The different parts of the sidewall flex different amounts so the tire crushes different amounts in different parts of its circumference. It'* like having different strength springs on different parts of the wheel as the tire; some compress a lot, some a little.

This causes up and down force which makes the wheel center actually go up and down as the tire rolls. This is the same as would happen if the tire were out of balance. The Hunter tells the technician where to add weight to counteract the up and down hopping force.

Some cars of the H group (and predecessors) had different amounts of stiffness in te frame. The light weight of those aluminum A-arms lets uneven wheel movement shake through the car. IIRC there was a TSB with different changes in rubber insultators in the suspension (A-arm?) to reduce that. The LeSabre was the only one without that as a very last option. I haven't heard much about people having those changes so they may not have worked out well.

Good tires with a force below 10 really help to start with. And having the perfect alignment made a difference on my car. I also believe the Michelin symmetry tires changes as they aged up to 20K miles and roll with a more even crush. I surmise the sidewalls actually break in and flex more consistently. I only had them rebalanced one time. Now I'm over 40K mi.

Nice informative post imidizol. Your neighbor explained it better than I did.

I checked with Tire Discounters (ohio) today while out of town on a trip. When I explainted to him my ongoing out-of-balance symptoms (3 sets of tires now; not have balanced out the way I like them), he said he has about 25% of late model GM full-size autos with the same problem. But hark! There is a TSB.

A local Pontiac dealer faxed him a tech service bulletin while I waited. I wish I had gotten the bulletin number but basically it said:

Symptom: Out-of-balance tire symptoms on 2000+ full-size GM vehicles. Yes, the Bonne was right in there! Article said to try Hunter 9700 Roadforce balancer to make sure road force is not excessive. If all checks out ok, and tires still appear out of balance, starting at 60-70 mph, replace the Control Arm assembly (A-arm is old terminology). There is definitely a revised control arm with different bushings. GM advised him that the parts counter dude will need the VIN to insure that the correct assembly is ordered.

When I asked for an installed price I was quoted $550-700. I asked why so much? His response was that the entire Control Arm assembly on each side has to be exchanged with a rivised assembly. I think I will suck it up and drive with the quiver. Actually, I was so stressed out on the way home that I noticed not the quiver.