Leak rate of a bicycle tire

Why are leaks defined in mbar · l/s? This is a frequently asked question to our leak test experts. We would like to answer this question with a quick and well known example – a bicycle tire.

For the bicycle tire, we have the following requirements:

Once filled up with the right pressure, we would like to have the tire to not lose more than 1,000 mbar within 6 months. Thereby we define a pressure loss over time. Assuming that the bicycle tire has a volume of about 1.5 liters, this leads us to the maximum allowable leak rate of a bicycle tire in: pressure (mbar) times volume (l), over time (s):

Q_{pV} \left[ \frac{mbar \times l}{s} \right] = \frac{1000 \ mbar \times 1.5 \ l}{1.5 \times 10^{7} \ s} = 1.0 \times 10^{-4} \ mbar \ l / s