Earlier today, I slid on ice into a kerb sideways on a housing estate at about 15mph - both wheels seemed to make contact at the same time (no damage to the wheels). Now, at dual carraigeway speeds around sweeping left hand bends, I have a high frequency vibration (not like wheel balance issues) that builds and then declines in severity about every two seconds. (when travelling at a constant speed). In a straight line there is no vibration. I suspect that the tracking may be out a little bit but I have been told by my local tyre fitter that they can not do a 4 Wheel Alignment. Could the problem be something more serious? Is it a main dealer job to check the alignment of all four wheels?