[pcmos]

Frankly I disagree, this is certainly a design mistake. Any self respecting engineer who designed an entire vehicle platform should certainly have taken into account normal vibrations resulting from tire anomolies and slight alignment error. Every time I drive my LeSabre on the highway I am reminded of why I have to pound 800 pages of vibration analysis into my head this semester. There is no question that any mechanic who examines the complaint will determine that it originates in the tire. Assuming the engine and transmission don't contribute much in the way of speed related vehicle vibration, all of the vibration you feel in a car originates in the tire/wheel assembly. There is also no question that cheap tires are not well balanced and that if we could assemble a tire and wheel with ideal balance, vibration would be eliminated. The tire and wheel vibrate at any speed, you only feel it when it strikes a resonance with some component between you and the hub. fortunately most parts are so irregular in shape and have so many nodes that resonance occurs in an infinately small range of frequencies, or at frequencies that would exceed the frequencies of vibrations resulting from the motion of the wheel assembly at normal road speeds. The job of an engineer is to do one of two things, either eliminate the possibility of resonance occuring with any given part under normal operation, or isolate the vibration using proper attachemts. There are only 8 significant points where wheel motion can transfer to the body in a LeSabre, 6 frame mount positions and the upper mount of both front strut assemblies. I can gauruntee you that the frame mounts are NOT stiff by performance car standards, in fact the design scheme used to attach the front frame of this vehicle to the body is one of just a few reasons why it doesn't handle like a BMW 7 series. By the way, the H body platform has been scrapped by GM, it was used in limited models throughout the late 90's and early 00's and is now dead, probably because of how poorly it was designed. The line that separates a serious luxury performance car from a boat like the LeSabre is very thin and very grey. Essentially if GM took the time that it takes to consider every aspect of the design with the same level of care and detail, you would be paying 80k for the car and it wouldn't be branded a Buick, but it also wouldn't vibrate at 70 mph. I have not had a chance to go outside and experiment with some different modifications to try and tune out the vibration. By clamping the frame along the rail that the control arm attaches to, I should be able to alter the natural resonance of the frame itself and raise it significantly. Obviously this will result in a little extra road feel but the resonance vibrations should disappear. Adding mass to the control arm is another option, but upon further examination, I am so confident that the extended stretch of un-restrained frame is responsible, I'm going to attempt to attack that first. Obviously modifications I make to the primary structural element of the front of the car require careful consideration and analysis. I have some prototype ideas in mind, concepts that will at least let me test my theory before making any permanent modifications. I just got done modifying and installing a new magnasteer rack, I altered the calibration using a tech 2 to reduce the assist overall and I re-built the inner ties using some bushings that I machined on my own. Before I can mess with the vibration I need to finish up the steering mods, the car already handles about 40x better, but thats for another post.