Pressure Loss in Tubeless Tires

A tubeless tire does not normally leak any more than a tube-type tire. The slight loss of
air from diffusion through the liner and vents of a tubeless tire is insignificant in the daily
operation of the tires.1. Reasons for Air Loss in Properly Mounted Tires -- The most probable cause of

leaks in properly mounted tubeless tire assemblies are:

a. Loose or damaged valve components
b. Cut or impact punctures
c. Cracked rim
d. Broken or burned beads
Detection of a leak requires some knowledge of air pressure behavior. The
temperature of the air in the tire affects the pressure; therefore, it is necessary to
make pressure measurements at relatively the same contained air temperature to
determine if air has been lost. This is the purpose of the "hot inflation check."

2. Finding Leaks Once the influence of tire operating conditions has been
eliminated as a possible reason for a drop in air pressure, the tire assembly should
be checked with a soap and water solution or soap spray.

a. The first step is to inspect the valve. Possible leakage areas in this part are
the O-ring seals, spud washers, valve core, extensions, and adapters.
b. Next, the outside face of the tire should be checked for penetrations which
can be caused by small metal objects or from large cuts and punctures.
c. The rim assembly is a third possible leakage source. The welded portions
of the rim base, including the gutter section and that portion of the bead
base band which can be seen, should be soaped.
d. A hardened or burned bead base, caused by hot brakes, can also cause
leakage, either by cracks or erosion of the material under the wire beads.
Separation may be caused around the bead wire, allowing the wire to
unwind and pierce the liner, or may cause beadouts and broken beads.
Beads may also break due to excessive strain. If beads are suspect, deflate
the tire immediately. Leaks under the bead can be detected by soaping the
bead base band and flange junction and the pry bar pockets. Also, soap the
opposite side of the rim assembly at the pry bar pockets.

3. Leaks from Improper Mounting -- An improperly mounted tire may leak due to
the use of a faulty O-ring. It may be the wrong size, damaged, or applied
improperly. The O-ring groove may also be pitted or chipped. Leaks in this area
can be detected by the use of soap solution at the junction of the lock ring and the
bead base band, and in the space at the ends of the split lock ring.
Leaks in a tubeless assembly are usually easy to trace and to explain by a
systematic inspection of the various parts. It is not necessary to demount the tires
in most cases. Soap solution will indicate where the leak is. If this is not the case,
then a more detailed inspection of the inside of the tire and the disassembled rim parts is required.