Originally Posted by
Velo Dog
In my experience (which is extensive but doesn't include carbon), tire size and pressure make more difference than frame material. I weigh about 20 pounds more than you do, and I do all my riding these days on 32mm or larger tires. I've done the same 25-mile RT commute for almost 30 years, 100 or more times a year, and there's no correlation between tire size and my times, whether I'm using 23mm or 41mm. Even if, say, 35s were a little slower, I'd ride them anyway. I'm only going to work...
I commuted for about 6 mos. on 38s. This wasn't necessary, because the pavement is good all the way, but I also used the bike for rough touring and didn't want to fool with swapping out tires. Then I stripped that bike down for painting and used my road bike for the commute--no panniers, just backpack--and I do find I arrive quicker by several minutes over the 11.5 miles. But at least part of this I'm sure is that when on my road bike I just want to pedal faster--it feels right. The experience has taught me that a commuter bike is of no certain configuration. It depends on the particular commute--whether the pave is good or crappy, whether most of it is bike path or in traffic, etc.
Then, on the comfort front, I'm really questioning whether steel has any advantage over aluminum. Doesn't this have a lot to do with head angle? My former Specialized Allez steel had 74 deg., while the Al frame that replaced it has 72.5 and is noticeably gentler over bumps. Steering on the Al is less responsive, of course, but it tracks by itself. Could it be that most Al bikes have had the steeper head angles, whereas steel bikes have come in a variety of angles and have therefore been reputed to be more comfortable?