Originally Posted by
frost_okc
...according to the Sheldon Brown site, that puts me at 22.9 mph at 80 rpm. Going to 13t would make it 24.7 mph at 80 rpm. So an improvement of 1.8 mph. Being able to cruise at 25 mph would mitigate the problem of people trying to pass me while in a 25 mph hour zone as well.
Again, this is not a math problem but a power/efficiency problem. Going from 22.9mph to 24.7mph (an 8% increase in speed) will require 16% more effort just to overcome wind resistance. That is true no matter what gear you are able to push at that speed, and whether you have a tailwind or headwind. If you want to go that much faster you either need to have 16% greater strength and endurance or you need to be more efficient in how you use what you have. Actually at that speed for any distance you will most likely need both. Few cyclists can maintain 25mph for long, let alone "cruise" at that speed.