No test drive after an alignment? That's like not looking in the mirror when trying on a new suit! The last step is always, "verify the repair". As a former suspension and alignment specialist at a very nice family-owned Chrysler dealership, I was never so arrogant as to think my alignments always turned out perfect the first time. A projector or mirror can slip on the wheel without you knowing. A wheel could turn left or right while you're performing the calibration procedure, or a projector could simply be out-of-calibration. I even saw my readings change when the guy next to me started using the acetylene torch. It interfered with the infrared light beams from the projectors. As careful as I tried to be, at least one out of five alignments needed some followup tweaking after the first test drive, and my bosses never once yelled at me for taking too long. They were very happy that almost no one came back with a complaint.
If the shaking only started with the new tires, one has a broken belt, or, if an old-style tire changer was used, a steel wheel could have gotten bent. You'll see those by running it in gear with the front end jacked up or with the van on a hoist. If nothing obvious shows up, have the tires balanced on a "road force" balancer. If that shows all four tires to be acceptable, suspect a worn inner cv joint housing. The clue there is the steering wheel shaking will be worse during acceleration up to about 35 mph. It will smooth out when not under load as in when coasting or cruising at a steady speed.
Check the tire wear patterns too for signs of feather-edging. If that is real bad, you'll be able to see it. When it's not so bad, the blocks of tread will feel smooth when you run you hand one way over them, but you'll feel the sharp raised edges going the other way. That is a sign that "total toe" is not set correctly and will always affect both tires equally. If both front tires are off by the same amount, the steering wheel will still be straight. If only one wheel is set incorrectly, the steering wheel will be off to one side on a straight road.
When total toe is off, the van will follow the tire with the most weight on it, (usually the right tire), and the other one will walk to the left or right, then spring back when the sidewall can't flex anymore. That can set up a shaking feeling.
A bent hub is very rare. They are too tough to bend while doing any kind of service work. If you slide into a curb, the wheel or strut will bend long before the hub will.
Also look for spots of rust or corrosion that got stuck between the wheel and rotor or between the rotor and hub. That wobble can be too small to see on a hoist but it will cause a shaking. Cast wheels often have chunks break off that stick to the rotor, then when any wheel is mounted there, that corrosion gets overlooked but it prevents that wheel from sitting squarely against the rotor. The same thing can happen behind the rotor while the wheel is off and not there to hold the rotor tightly against the hub.
There are also one or three access holes in the hubs. Water and salt can get up there and form raised areas of rust on the back side of the rotor. Those spots must be scrapped off when the rotors are machined. If they aren't, the rotor will wobble on the brake lathe and a new wobble will be machined into it. If the rotor is reinstalled on the hub in a different orientation, that rust spot will hold it away in that area so it doesn't sit squarely against that hub. That will make the rotor AND the wheel wobble.
One last clue to a tire problem can be found on front-wheel-drive vehicles during a test drive. If the characteristics of the two front tires are different, the vehicle may pull one way under acceleration and the other way during moderate to hard braking. You may solve that by switching just the two right side tires or just the two left side tires.
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Tuesday, January 10th, 2012 AT 1:53 AM