Originally Posted by ginsoakedboy

But tires and wheels aren't the whole story. In general (there are always exceptions, and I'm sure someone will be along to point them out), the mountain bikes are often beefier and heavier, and the geometry is different to achieve a more upright ride instead of the more efficient riding position that you find on a road bike. These factors also contribute to why your road bike feels "zippier". I regularly ride both my road bike and a hybrid that I use more for commuting and errands. Even though both have 700c wheels with comparable size tires, I average about 2 mph faster on the road bike because of the different configurations.