Originally Posted by
old's'cool
I doubt the extra mass of "heavy" tires is holding you back as much as you seem to think, but rolling resistance certainly is a critical parameter no matter what the riding condition.
I have no doubt that heavy tires don't make a significant difference in the actual speed of a bike, and maybe not even its acceleration, but they feel a lot different. If the tire is also hard that's even worse. I don't really care how fast I'm going so much as I care about how much I'm enjoying the ride.