Depending on how you measure the changes:
4.53 to 4.11 = ~10% difference
4.11 to 3.90 = ~5% difference. I noticed/felt this difference.
4.11 or 3.90 to 3.55 = a difference you can "feel"
The "calculator" at the bottom of this page gives a good "depiction" of RPMs at with various "set-ups" at various speeds.
