Hardly noticeable on road really, placebo effect I'd say. Don't think any of us can say we could tell how much is in a tyre off the top of our heads. Have to be about 3 or 4 psi down before most would know if we're honest. If you are giving it a genuine 100% balls out track thrash, then you might feel it. Our genuine racers would probably feel it but not the majority. Sure a would be hero will disagree lol. I've heard that certain race teams, when looking for a new driver will do this type of test to see how much they notice the difference, to compare one driver to another.