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The first thing I'd do is check the tyre pressures on all tyres are up to the maximum shown on the door jamb sticker and if OK then take the car to a place that does 4 wheel suspension alignment, most places use the back wheels as a datum and assume that they are perfectly straight and true. Often this is not the case and many modern cars are now adjustable at the rear as well as the front.A 4 wheel alignment measures all four wheels independently and each is set -up without referring to each other.
it also worth checking for a tyre defect - any cracks or bulges on the side-wall of the tyre (inside and outside) these will throw the tyre out of shape and produce vibration - take a good look over the tyre sidewalls and bear in mind that anything that looks suspect when static will probably be ballooning out and far worse at speed so if any doubt then replace the tyre. Also check if the tyres have been fitted the right way round as some types are directional
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