Tire Pressure

    The other factor in the equation is tire pressure. Tire pressure is surprisingly complex, in that its affected by everything from your rim width to how much you brake on descents to the change in temperature to you weight. More importantly, maintaining the optimum tire pressure will ensure less energy is used and that you will have the right level of traction and necessary level of handling and stability from the tire for the road conditions you are encountering at any point during a ride under any condition. 

    For example, a properly inflated bike tire conform to bumps and absorb shocks. An overinflated bike tire transmit impacts to the rider, which sacrifices speed and riding comfort. On new pavement, 
    your tires might feel great at 100 psi, but on a rough road, they might roll faster at 90 psi. In wet conditions, you may want to run 10 psi less than usual for improved traction. And if you're a mountain biker who rides to the trailhead, keep in mind that while your bike rolls smoothly on the road with 50 psi, it might feel better on the singletrack at 38 psi. 

    Another example is that for each 10-degree-Fahrenheit drop in temperature, your tire pressure drops by about 2 percent. So if the temperature dips from 90 degrees to 60, your road tire pressure 
    would drop from, say, 100 psi to 94 psi. Those six pounds of air pressure are noticeable and worth 
    adjusting for.