Have you encountered vehicle vibrations caused by road tar? They're far from the Beach Boys' “Good Vibrations” variety. You can add road tar accumulations as another potential cause of nasty vibrations on otherwise good tires.

What happens if you get tar on your tires?

If it's only on your tires, then don't worry. It will eventually harden and chunk off while driving. If thick enough, it could make highway speeds unbalanced, in which case you'll want to mechanically remove it.

What causes tires to shake while driving?

The most common cause of vehicle wobbles in this speed range is a bent wheel or mildly out of round tire. ... The most common cause of vehicle shakes at 50 mph or higher is tire balance. Again, transmission or drive lines can cause this, but the tires should be the first thing to have checked.