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Tire Pressure
More temperature sensitive than you might think

By: James R. Davis

As we are now into the colder months of the year I thought it appropriate to post a reminder about tire pressures and the effect of temperature on same.

Stamped on the outside of many of your tires is a recommended tire pressure range. (At least an upper limit.) For longest tire life it is my recommendation that you strive to keep them at the higher limit of those recommendations (regardless of what your motorcycle owner's manual might say to the contrary.) Further, this pressure should be determined while the tires are cold - meaning, have not been used for a couple of hours.

Time and outside temperature effect the pressure within your tires. It is NORMAL for a tire to lose about 1 pound per square inch (psi) per month. Outside temperatures affect your tire pressure far more profoundly, however. A tire's pressure can change by 1 psi for every 10 degrees Fahrenheit of temperature change. As temperature goes, so goes pressure.

For example, if a tire is found to have 38 psi on an 80-degree mid-summer day, it could lose enough air to have an inflation pressure of 26 psi on a 20-degree day six months later. This represents a loss of 6 psi over six months and an additional loss of 6 psi due to the 60 degree temperature reduction.

At 26 psi, your tire is severely under inflated and dangerous!

There is nothing wrong with your tire if it behaves like this, of course. What is being illustrated here is that you MUST check your tire pressure on a regular basis (about once a week is reasonable) and to be particularly aware of it on cold days.

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(James R. Davis is a recognized expert witness in the fields of Motorcycle Safety/Dynamics.)

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