I had some steer tires a while back that would set up a death wobble at just about any given speed if the road conditions would get really squirrily like where the log trucks had some nasty ruts wore in on a curve. New set of skins did the trick
Broken belts are not good. This one came really close to letting go at my usual cruise speed. Noticed a shake that was getting worse on the way home so I limited myself to below 60 MPH. Tire had almost 0 miles before I installed it but the age was unknown.
I'd look at that sooner than later because a high speed blow out isn't funny. Mine was on the front too.
That looks like a Firestone R4S; what brand tire is it ??
As for being on the front, a front blow-out is a lot easier to control than a rear (on a SRW truck, of course)
uniroyal if I remember right.