Originally Posted by
HerrKaLeun
Narrower tire will FEEL faster because you will bounce more at a given speed. But unless the pavement is 100% smooth, the wider tire will be faster.
Get a tire of the same size with more efficient rubber and tread. However, unless you have knobby tires, tires contribute little to effort required.
If you're not riding on gravel 40mm Schwalbe G-One All arounds are much slower. If you're riding solo for exercise it doesn't make a difference how fast you go but if you're commuting or trying to keep up with a group some 28mm slicks would be significantly (~2mph) faster.