I'm struggling trying to identify this noise. Recently I changed the rear brake pads. I'm unsure if this has anything at all to do with the noise. After the noise started I changed out the right front axle. Seems to have made no change to the noise although there was no question the axle needed changed.

The noise is more obvious after I have been riding for awhile (maybe 15, 20 minutes). I can feel it before I can hear it. It starts out as a low rumble kinda like going over a light rumble strip on the road. The longer I drive the more frequent and less subtle it becomes. At times if I take my foot off the accelerator it appears to go away. At times it does not. It "FEELS LIKE" it is originating from the right rear. But it is so subtle I am not really sure.

I can not feel any parts heating up after a ride. Using my hands wheels, axle, hubs, caliper housing's,,,, all cool to the touch.

Best description of the sound:

Brrrrrrrrrr,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Brrrrrrrrrrrrrrrrrrrrrr, brrrrrrrrrrrrr,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,,,,,,,,,,,,brrrrrrrrrrrrrrrrrr. Is does not have a consistent pattern.

Any help would be greatly appreciated
Thanks in advance
Bryan