Originally Posted by Fat Boy

Just as a person from the general public isn't plopped in the seat of a test car from a auto manufacturer, you wouldn't drop joe-blow on some bike to test. You'd use a rider who could accurately detect small changes. These people exist. I'm not saying I'm one of them, but there are guys, specifically ones who are trained this way, who can discern 5 psi in tire pressure and/or other subtle changes. He may or may not be a pro racer. That certainly wouldn't be a requirement.

If you're trained to pick out different sounds and feelings, they are not all that tough to notice.