Alignment won't cause your vehicle to vibrate. If you are starting to get vibrations at high speeds I would suspect either a tire imbalance or a bent wheel is the culprit. I typically get my tires balanced every 3-5k miles depending on the severity of the vibrations and it will usually clear that right up. If you can feel the vibrations in your steering wheel that would be your front wheels, if they are coming from your seat its the rears.
Vibration issues could also be caused by worn control arm or stabilizer arm bushings and worn hub bearings. If it was bushings or bearing though, you would likely feel it at lower speeds as well.
As far as alignment, Toe and Camber are adjustable with tie rods and control arms respectively. Caster is typically not going to be adjustable.
Also, there is a lot of confusion about a "roadforce balance". There is a roadforce test, which can help with "match mounting" the imperfections of the tire with the imperfections of the wheel to reduce corrective weight and help eliminate balance issues inherently since it applies a force to the tire assembly and reads the amount of force pushed back against the rolling pressure. If there is a section of tire that is harder or denser and there for springier than the rest of the tire, that can be measured. If it is severe enough, then the tire can usually be replaced with the manufacturer as defective if it is new. That requires new tires (since worn tires cannot be accurately tested, they can be tested, just not accurately for roadforce) to be mounted, inflated properly, tested, deflated and rotated on the rim for matching, then retested. Balancing is the last step, and isn't actually part of the roadforce process, its a regular spin balance. Any good computer spin balance should get your wheel assembly rolling smooth, unless you have unevenly worn tires, bent wheels, or an inconsistent tread build which seems to happen primarily with less expensive tires, but could happen to any tire.
Last edited by Phillip@BMPDesign; 10-02-2012 at 08:52 AM.
Reason: To include roadforce notes