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It is a common misconception that pressure is simply proportional to performance. There is no universally correct pressure, as different situations require reconsideration of a number of factors.

Nobody likes getting dropped, so many riders prioritize rolling resistance when inflating their tires. As a section of tire spins down to the ground and back up again, it is compressed by the road and then allowed to re-expand as it comes back up. The efficiency and elasticity of this deflection is a critical characteristic of the tire, and a more 'supple' tire deforms and reforms more easily. But whichever tire you've chosen, the rolling resistance caused by deflection can be decreased by decreasing that deflection. A more firmly inflated tire deflects less, and in this regard, rolls faster.

But, as it is pumped more firmly, a tire's ability to smooth out the imperfections in a road surface will decrease. This is not a consideration of comfort alone -- all the energy in the vibrations of your bike and forearms is traceable back to the muscles in your legs. Of course, the severity of this effect is dependent on the quality of the road surface. On brand new business park pavement, pressure at or even above 140 is reasonable. On an indoor wooden velodrome, look for pressures in the low 200's. As your road surface gets rougher, slightly lower pressures (around 120) are least resistant to rolling.

But rolling resistance is only part of the deflection story. The amount that your tire deflects also dictates how much of your tire is making contact with the road, and therefore, how much grip you're getting. Look over the shoulder of an experienced racer as she pumps her tires up for a dry criterium on perfect asphalt and you'll probably see her stop near 100. Her first priority is being able to rail it confidently through the corners. If the clouds open up and soak that perfect pavement with rain, she may stop at 90. When fall rolls in and our racer is topping off her cyclocross tubulars, she'll stop in the 30's. No kidding.

But remember, there are healthy limits to any approach. Tires that are insufficiently inflated are prone to pinch flatting -- where the tube is pinched between the rim and the tire when the rider bottoms out on a bump in the road. Even worse, it's possible for an under-inflated tire to roll off the rim.

Pump a tire up too much and you can explode it or blow it off the rim. Additionally, many lightweight clincher rims will bend or break under the strain of an overinflated tire, so it is crucial that you know your clincher rim's max inflation pressure as well as your tire's. These over-inflation catastrophes won't necessarily happen at the pump, either. Sometimes it takes a sharp corner at speed to push your strained equipment past its limit...so pump wisely. Blindly pumping every tire to its Max. Inflation is an ill-advised and dangerous practice.

Lastly, remember that pressure changes. First off, the above pressures are typical to riders between 150 and 180 pounds. Lighter or heavier riders need to consider the amount of downward force from their body weight and how it affects the pressure in their tires. For fun, have a friend pump up your tire while you're on the bike and watch the gauge as you get off. Another consideration: your tire pressure will increase while you ride if you start in the chill of pre-dawn and continue through high noon on a hot day. Plan accordingly if running your tires near their limits.

Road Racing Tire Pressure

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