Cycling is a game of inputs and outputs: how much power you’re able to produce in your legs vs. how much of that power is actually put to use in propelling you forward. Of the four main obstacles you have to overcome while riding — aerodynamic drag, gravity, rolling resistance, and mechanical friction — mechanical friction is the least significant, but it’s far from zero. US technical editor James Huang takes an in-depth at how much friction there is and what we can do about it, but also easy and inexpensive things to do at home to ensure we’re making the most of our efforts.