Deep ‘thrumming’ vibe from chain set when in top gear?

[Sloth]

I have had a GRX 1x11 fitted in place of the 105 2x that the bike came with.
The bikes a Giant Fastroad Advanced 1 (2022).
We all know the annoying clicking of chain rub when in the largest rear gear and at one extreme of chain angle.
We’ll, imaging the other extreme when in the smallest rear gear.
Instead of a clicking or typical chain rub sound, I get a very low, thrumming sensation at the opposite end of the sound spectrum to typical chain rub.
It only happens when I’m in the smallest gear (remember it’s a 1x)
It’s also almost like I feel some drag or resistance when pedalling in that gear, as if the front chain ring is somehow not aligned and causing this weird low thrumming vibration with every pedal stroke, but only in the highest/smallest rear gear.
It’s not ruining my rides but it just doesn’t feel ‘right’.

 

[C R]

I have had a GRX 1x11 fitted in place of the 105 2x that the bike came with.
The bikes a Giant Fastroad Advanced 1 (2022).
We all know the annoying clicking of chain rub when in the largest rear gear and at one extreme of chain angle.
We’ll, imaging the other extreme when in the smallest rear gear.
Instead of a clicking or typical chain rub sound, I get a very low, thrumming sensation at the opposite end of the sound spectrum to typical chain rub.
It only happens when I’m in the smallest gear (remember it’s a 1x)
It’s also almost like I feel some drag or resistance when pedalling in that gear, as if the front chain ring is somehow not aligned and causing this weird low thrumming vibration with every pedal stroke, but only in the highest/smallest rear gear.
It’s not ruining my rides but it just doesn’t feel ‘right’.

That sounds more like the rear wheel bearings to me.

 

[fossyant]

Potentially it's the chain angle. GRX chain line is a little further out than standard. I assume nothing is 'worn' ?