Originally Posted by
spare_wheel
If you want to ride fast you need to get a decent sub 25 lb bike, get a real crank and casette (e.g. 52-39 and 11-23/25), run high pressure skinnies (23-25 @ 110-130 psi), go clipless, and learn to spin. It also helps to have a healthy disrespect for minor car-centric traffic laws!
Bike weight isn't going to make a measurable difference on flat ground. On 6% grades at 250W a 145 pound rider atop a 30 pound bike instead of 25 one is going to drop from about 10.6 to 10.4 MPH. Differences will be less pronounced for flatter terrain and with heavier riders.
I skip wide range cassettes like that (11-23 has no 18 cog with 10 in back, and 11-25 doesn't even include a 16) in favor of tighter cogs in a more useful range. With 9 cogs and 50-34 I like 13-14-15-16-17-18-19-21-23, although I got a 12-23 to go with my upgrade to 10 cogs for a better chain line on the small ring and ordered a 14-15-16-17-18-19-20-21-22-23 cassette to see how a 20 cog works probably with a 53-39-30 crank from my bike shelf .
On a fast commute I spend half my time somewhere between 18 and 21 MPH spinning 50x21, 50x19, or 50x18.
On the rare occasion I break 30 MPH where a stop light pedestrian sign is counting down seconds it's using a 50x16.
Bigger gears wouldn't buy anything beyond fewer shifts to and from the small ring.
I also run my 25mm tires at 95-100 psi rear and 90-95 front with my 180 pounds of flab and 15 pound pannier. The rolling resistance increase is negligible and it's more comfortable without being soft enough to pinch flat on potholes or other road imperfections one of which was enough to bend a 400g rim. The pannier makes for a 20% drag increase but is way nicer than having the weight on my back.