I have not made any speed comparisons of our Calfee compared to our old Santa Sovereign. Both have relatively fat tubes. But I definitely feel more confident going downhill at high speeds on the Calfee especially when the road surface is bad as it absorbs bumps much better than the Santana did which would have a tendency to bounce around. Since our highest gear is 50x12 we are coasting at anything above 35 mph and I don't really care if I am pedaling at those speeds. For me downhills are an opportunity to rest and get my butt off the saddle, not to break any speed records although pretty sure we have hit 50 mph on occaision.