I've recently purchased a 2001 S55 with a couple of niggles. The main one being that the back end is extremely twitchy going over anything more than a manhole cover at 30mph. The rear suspension is creaky, but I'm fairly sure that's just the old bushes that I'll be replacing soon, so I'm thinking perhaps that the rear wheels are out of alignment? Seems logical that if they were, they'd pull the car in a slightly different direction when one wheel lost some traction, which is what it feels like. Any other ideas? Can't see anything immediately amiss.