Nov '76
Breakage of Dual Tandem Valve Stem Extensions
1. The inner duals on the CCE-IHC 20 Ton Dump Truck are equipped with valve stem extensions, since the offset of the
disc wheels with 12.00-20 ML (Mining and Logging) tires will not allow clearance in the wheel's hand hole to remove the
valve cap, check the tire pressure, and inflate the tire with the available length of valve stem in the tube. The valve stem
extension serves the purpose of bringing the tube's valve stem outboard, where the tire can be routinely serviced without
removal of the outer dual As is stated in the manual, the CCE dump truck's tire inflation is very important to obtain
reasonable tire life and prevent possible tire fires from under inflation. Therefore, these extensions should receive
maximum care and attention.
2. The tube's valve stem is brass and the valve extensions are brass. There have been reports that the extensions were
originally installed far too tight. Inspect the trucks and replace those extensions having stripped threads or crushed
mating surfaces. When reinstalling the extensions on the valve stem, be aware that the brass metal is soft. Tighten only
to the point that the extension is secure and air tight without damaging threads or the tubing barrels. Do not forget to
always reinstall the valve caps to keep the air in the tires and exclude dirt from the valve core seats.
3. Normally, rocks between the tires won't do much more than bend these soft metal extensions. Prolonged spinning of
the rear tandem in mud and in brush could cause breakage. Part of the PM servicing of the truck should be to insure that
the valve stem extensions are functional, because if the truck user is unable to check and inflate the inner duals, the result
will be running on under-inflated tires. The truck's only contact with the ground is through its 10 tires and they have to
carry their portion of the 65,000 to 70,000 pounds of loaded truck. These valve stem extensions, then, are certainly one
area in which "ZERO DEFECTS" need to be practiced,
4. Do not take the "easy way" out and leave both the extensions and the valve caps off, figuring the inner duals can be
checked and inflated by pushing the chuck on the wide-open valve stem of the tube. Dirt will get lodged in the valve core
seat and result in a leaker with continual, under-inflation. The inner dual is the bad place to have a leaker and a worse
place to have a tire fire that could destroy the truck.
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