Monday, January 11, 2010

proper air pressure

There are a lot of questions out there about how much air a road bike tire should have.
This has been a hot topic among wheel and tire manufacturers and most of the major companies have put a lot of time and money into testing what is really faster. Nearly every test had the same results. Most people were a little surprised about the results. The tests showed that the pressure that had the least amount of rolling resistance was actually around 90 psi. The general rule of thumb up to this point was the higher the pressure, the less resistance you had. Most people simply aired their tires up to whatever the tire was rated to. What the tests showed was that when the tires were aired up to more than 120psi the tire actually bounced on the small bumps that all pavement has. This bouncing caused the tire to lose momentum and it took more effort to keep the tire going at the same speed. When the tire was aired up to 90psi the tire deformed over the bumps and kept the momentum going. This same result also showed up when using 23mm tires versus smaller "faster" tires. The 23mm tires deformed over the bumps and the 19mm tires bounced on the bumps. If you want to know more about these tests, here is one that is pretty good and it shows you how to figure out exactly what your perfect pressure is for you weight and tire size.


No comments: