SECTION II. EQUIPMENT DESCRIPTION AND DATA (Con't)
1-8. EQUIPMENT CHARACTERISTICS, CAPABILITIES, AND FEATURES (Con't).
i. RIM TYPES AND VARIATIONS.
General to Multi-Piece Rims, with Lockrings or Siderings. Any time a tire is changed,
or during regular inspections, the rim components should be inspected for cracks, breaks or excessive rust.
When mounting rim/wheel combinations with a split lockring or sidering make sure the gap is aligned 180
degrees from the valve. Positioning the gap at 180 degrees will minimize distortion. During manufacturing
there is a piece of metal taken out of the rim where the valve goes which creates a natural weak point. The
gap is a weak point and a pressure point also and if they where incorrectly lined up the wheel could
distort. There is no maximum lockring/sidering gap for two and three piece assemblies. However there are
minimum gap tolerances. For two-piece rims with a lockring/sidering, the gap, when assembled should
not be less than 3/8 inch. The ends on the lockring/sidering on three piece assemblies, such as on the
HEMTT vehicle, should not touch, when assembled.
Drop-Center Rims. Drop-center rims are one piece and are permanently fastened to the
wheel disc. The important feature is a well that permits mounting and demounting of the tire. Bead seats
are tapered to match corresponding tapers on tire beads. Drop-center rims are commonly used on smaller
vehicles, such as passenger cars and light trucks but occasionally may be used on larger heavier vehicles
also (e.g. military M747 Heavy Equipment Trailer uses a drop-center rim).
Drop-Center Rim with Safety Ridge. Some Drop-Center rims are constructed with an
added safety ridge at the edge of the bead ledges. If a tire goes flat, the ridge will prevent the tire bead
from slipping into the well, which might cause the tire to separate from the wheel sooner.
Semidrop-Center Rims with Removable Side Flange or Lockring. Semidrop-Center
rims have shallow wells and beveled bead seats to fit the taper of the tire beads. They have demountable
flanges or lockrings that fit in the gutter on the outside edge of the rim. One of the bead seats bears on a
non-removable flange and the other bead seats on a removable side flange.