1996 Fleetwood Southwind, F53 Ford, 35 ft. At about 40 to 50 mph I get a vibration, smooth except for that speed. Did it with the old tires, does it with new tires. Feels like a bad universal but they look fine, I grease then often, no play that I can find, no rust around any of the caps. This is the first vehicle I've owned with center support bearings, it has 2 of them, and I don't know how to tell if they are OK or not. Nothing is obviously wrong. I can lift one of them about 1/4 inch, maybe less, looks like maybe the rubber part of it has partially failed? No unusual noises. MH has 123,000 miles, I've put about 50,000, don't know if they were replaced before I bought it. Thanks Much.