Too much air gives you a quick ride, Guy Andrews notes in “Road Bike Maintenance,” while too little gives you a comfortable, but squishy spin. That's why road bike tires bear the tire pressure specification; typically for a specific tire a range such as 95 psi to 105 psi. Trial and error will help you arrive at the best pressure for your road bike tires. Check your tire pressure before every ride to see how much more air to add.
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Road tires generally require 80 psi to 130 psi, mountain tires 30 psi to 50 psi and hybrid tires 50 psi to 70 psi. To find your ideal pressure, start in the middle of your range and factor in your body weight. Never go above or below the manufacturer’s recommendations.
Bump in the Road
Higher tire pressure equals lower rolling resistance because hard tires flex less and create a smaller contact patch. But bumps exist in every road, so that an over-inflated tire will transmit impact to the rider. Adjust your tire pressure depending on the situation presenting itself during your ride.
On a new smooth road, your best tire pressure might be 100 psi, but bring it down to 90 psi for a rough road. In drizzly or rainy weather, also lower the pressure by 10 psi for improved traction. For every 10-degree drop in Fahrenheit temperature, your tire pressure drops by 2 percent, such that a drop from 80 to 50 degrees translates to a drop of 100 to 94 psi. Add more pressure to compensate.
As with car tires, bike tire inflation is important to performance. Bike-tire engineers look for optimal deflection, or expected flexing, for the best grip, comfort, efficiency and comfort. The most important variable affecting the ideal amount of tire pressure is the load your tires need to carry. For riders who weigh more than 180 lbs., inflate to the maximum pressure indicated on the tire sidewall, recommends one tire manufacturer. For riders who weigh less than 110 lbs., inflate to the minimum pressure. For its 700x28C and 700x32C tires, the range is from 58 psi to 80 psi; for its 7000x25C tires, 73 psi to 102 psi; and for its 650x23C tires, 87 psi to 116 psi.
Gauge the Situation
Keep a simple pencil tire pressure gauge in your tool kit. A sliding rod pops out and indicates the tire pressure. Or you can try a fancier model with a dial readout. Buy a gauge designed for the higher pressures of road bikes rather than one for automobiles. Or use a floor pump with a built-in gauge to correctly pressurize your tires.