Vibration diagnostics

Had steer tires develop bad cupping wear like that on a 2 year old freightliner straight truck. Turned out to be the front springs would sag and kinda roll back when loaded and cause steer axle to rotate back and move out of plane a degree or two to one side. 6 rack alignments and 3 sets of michelins got wasted before a great alignment guy who does them mobile out of a service trailer said he’d check it fully loaded and bingo.
Pulled springs and took to a spring shop. They added a helper leaf and installed new shim and u-bolts and had alignment done loaded. Problem solved.

 

They don't call it a freight shaker for nothing! I'm so over Freightliner after having 3 over the years and dealing with all of their shenanigans, poor customer service, quality or lack thereof

 

I've just replaced front springs, ds looked a little flatter to me. I am very hopeful that this will at least cure that weird cupping wear. Still cannot quite understand this dadgum vibration though...

 

Is it kinda like this going down the road?

 

Almost, if they had Parkinson's while they're bouncing...

 

Have you ever had the hub's, bearings, races checked on the steering axle? Also kinda sounds like tie rod ends?

 

I was thinking yesterday that i guess i haven't really done anything with the hub yet but i have the rest. Tie rod is only about 2 years old and was in good shape with alignment along with the rest of the steering components. Steering has always been real good and tight. Shop hand was reffing on tire while i watched King pins, barely about a 32nd movement on steer and not even anything visible on ps king pins. Had the steer axle wheel bearings replaced summer of 18 with all brake hardware and drums. None of this has made any impact

 

So what turned out to be the solution?