New tubeless tyres - New valves and valve stems

When fitting a new tubeless tyre onto the tubeless-type rim of your motorcycle, you should always use a new valve. We highly recommend this because the body of valves used in tubeless rims is made out of a rubber material, which will harden and age over time. The aging and hardening process is accelerated when the valve comes into contact with oil, ozone and other hostile elements. When braking or accelerating, the valve is bent by dynamic forces. An old valve could brake under such forces and cause a sudden air loss.
Pirelli recommends the use of short valve stems. At high speeds, the strong centrifugal forces work on the valve and the tension of the spring. The air pressure is not sufficient to keep the valve closed. Due to a smaller mass of short valve stems (compared to long valve stems), the valve remains closed at high speeds.

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