Steering Wheel problems of the 2010 Hyundai Elantra

I was driving on the highway and was cut off by another car. I was travelling about 50mph, I proceeded to brake (did not require hard braking, because me speed was not high) and steer to the right to avoid hitting the right side of the car that cut me off. My car over compensated and proceeded to swerve. It took a lot to regain control. My initial steer to avoid the car in front was not significant enough to cause the vehicle to swerve out of control. I have never experienced this with other vehicles that I have driven and this experience was rather frightening.

I took delivery of the brand new car & about a mile down the road I noticed prominent bounces after the car would go over bump in the road when the car was decelerating to a traffic light. I felt a total of three bounces with the first being the largest, second half of first, third half of second, & fourth couldn't be felt. It was bumper to bumper traffic & going light to light. The bumps were raise sections of the road affecting all four tires. The bumps were not potholes. I emailed my salesperson the next business day of the problem with no response. My main concern is highway driving. One stretch of highway has cement slabs in an undulating pattern that I have driven over daily for a very long time at many different speeds & in many different driving conditions. My previous car would react by rumbling up & down. That sensation was constant over the years at any speed & driving condition. Once I cleared that section of the bad highway, my car would immediately stop. The first time I went over that same stretch of highway in my new car at an est. 60-65 mph, the car begin to oscillate harmonically (bounce rhythmically) & continued to harmonically oscillate (bounce) once I cleared that bad section of the highway for an additional minute. I estimated the total time at two minutes. The harmonic oscillation felt very consistent over that two minute stretch. Once I went over another bump the oscillation went stopped. The struts are supposed to dampen the oscillations. I brought it into the service department. The mechanic test drove it & said the suspension felt firm. The suspension checked out ok (no numbers given). It has a sport tuned suspension & was suppose to do this. The mechanic didn't drive the bad section of the highway because it was too far away. I will try to resolve this matter with the Hyundais field service engineer.