1983 911SC. I had a vibration so I I'd had new tires put on at some place, vibration still there, had rear rotors replaced, which cured some brake pulsing but vibration still there, replaced shocks and strut inserts, vibration still there, got a road force balance at yet another place, still had a vibration, contemplated pushing it off a cliff, vibration still there, then took it to Chet's. Got a road force balance at Chet's and voila! Vibration gone! I could almost buy the guy flowers! Four-wheel alignment for good measure and the car drives like a charm now, like it hasn't in longer than I care to think about. Shoulda gone to Chet's first. True story.