spacers cause vibration?

[eclou]

while modern tires may not permanently flat spot, they can deform temporarily and cause a vibration. Many tires still use steel belts which you will see if you ever cord a tire at the track.

I get this sometimes on a car that I drive once a week. Usually some driving will eliminate it but you can also over inflate the tire (not to dangerous levels but just beyond car spec) to help quickly resolve it. The tire may have a max of 50 psi and the recommended fill for the car may be about 28-35 psi, so you can bump it to 44 psi or so, run it for 5 minutes then deflate back to normal.