Sounds Like A Flat Tire, but it's not?

This is not all the time, but sometimes my car sounds like it has a flat tire as I am driving it. It doesn’t make that sound when I stop. The brakes don’t grind. I don’t think it’s a wheel bearing. Any suggestions???

CV joints

Tire tread separation. Makes a funny slapping sound that gets worse the faster you go…

I agree that tread separation is a likely source of that noise. This can be dangerous, so have it checked out.

You can get this checked by having the wheels spun on a balancing machine that does “road force balancing”. Not all shops have them. This spins the tire with an artificial load applied (a drum pressed onto the surface of the tread). That detects internal tire faults that regular spin balancers can’t.

Could be a stretch of bad highway.