I have a Trek Navigator 300 "comfort" bike that I've noodled about the neighborhood for the last three years with my kids on. This spring I took it into my head to start doing my 25 mile RT commute on the bike. I swapped the tires to 26 x 1.5 road, changed the sprung saddle for a Serfas Cosmos and set the adjustable stem as far forward and low as possible. (I also added panniers, fenders and lighting, which has no bearing on the question). I find I can run my commute at a pretty consistent 15-17 mph when moving and I can make the 12.5 miles each way in about 50 minutes.
I also notice people on this forum riding much more aggressive road oriented bikes. Assuming that I'm partial to at least a bit of a heads up stance for traffic and I like flat bars, is the comfort bike frame really holding me back? Could I be running 20mph with different geometry?
Also, what is really different with my frame? From what I can tell, the seat and head angles are greater, which appears to place the seat further back from the bottom bracket. I assume the reach from seat to bars is also different, though hard to quantify. Maybe what I'm also trying to ask is, what exactly is the difference between an agressive and a relaxed frame?