I went from a 34MM deep rim to a 46MM deep rim and lost 185 grams of mass. My butt meter sync'd with my bike computer seems to show about .5-1.0 MPH increase in average speed on the same 2-3 hour rides I have done for years. I have noticed that with the same amount of effort I can keep the bike 1-2 MPH faster on the flats than I could in the past at the same fitness levels. It also could just be a big fantasy I have created to justy spending money on a new wheels. Either way I am happy.