My 2000 Buick Le Sabre Limited has 46,000 miles. The car shimmies at 50 MPH. The tires have. B balanced and aligned. New struts, new right front axel, new front and back brakes, my mechanic says tie rods and ball joints are good. Tires inspected and no bad belts. Tires rotated many ways. All this has been done including new air shocks in the rear. My mechanic is stumped any words of wisdom.
Check the engine mounts. I think they are fluid filled. This car is very sensitive to highway bounce, if the fluid has lesked outmof the mounts it can make this worse. You might also try having the tires checked on a road force measurement machine.
there are a few things to eliminate and see if one of them fixes the problem first of all is it the front or rear tires that shimmy , sometimes its deceiving when a rear tire feels like its the front. so after that have the rear aligned., next if its the front tires have them aligned and balanced on the car with a special machine most good shops have them., last of all replace the tires one could have a steel ply bubbled inside , text
I really can’t answer your question positively, but I can from being a Nascar fan tell you that not all pairs are made the same. Some tires come from the factory and they’re just not right. As an extremely Last Resort try a new set of different tires. I see it every week in the races where one set of tires doesn’t perform the way they’re supposed to and as always this is just my opinion
Has anyone checked the rear suspension for deteriorated bushings or bent parts?
Also look for axle bearing problems or maybe a drive axle that isn’t running true. 50 mph is a good point for driveshaft problems. Don’t rule out tires either. Sometimes uneven tire pressure will make a difference.