@stinkyface Sorry it took me so long to get back to you. I tried what you suggested and it turns out there's a small area on the tire that feels "flatter" than the rest. It's not a bump, on the contrary in fact, but it would still explain what I was describing. I'm surprised and a bit amazed that this can make a difference in the "road feel" :)
Most of my miles are not on smooth blacktop here in Canada, far from it, so if it's not detrimental to the OW itself I can live with that tire. Thank you so much for helping me find an explanation!

I've been noticing a vibration when riding my OW Pint and its frequency seems to match the speed I roll at.
The effect is as if I had a hard bump on my tire or if it was egg-shaped instead of round but I can't see anything wrong when I inspect it.
My tire pressure was at 16psi when I noticed so I adjusted it to 20psi and tightened all the visible bolts but it did not stop.
Anybody had something similar or suggestion on how I could investigate further?
Thanks.