High speed vibration
 

With the stay at home order, my car has been parked for a while. While it was sitting I changed timing belt and water pump. I was going to go for a spirited run and checked my tire pressure first. They were like 20 lbs.

During a higher speed section, around 115-120 mph there was a disturbing vibration. Felt like drive train, not in steering wheel. All bearings and axles have less than 4k on them. I'm going to take the wheels off to check balance. Could I have an out of round tire from sitting? How would I diagnose that. Driveshaft has maybe 10k on it. Any advice on what to do?

​​​​​Vibration occurs under wot and more gradual load. It's perplexing to me and that I can't feel anything until I am at a speed that will kill me if something goes kaboom. Any thoughts are appreciated. Sorry for the long post.

I recently bought a car that had sat for a long time and it had similar symptoms, but i certainly dont drive triple digits on the streets.

how i solved it was inflating the tires over what i normally would (i went to 34psi) and a good highway drive (70-80mph)

Did what waffles said. 35 lbs. of air and 20 miles around town. Sat for a day, then lowered to normal and no more vibration.