ZZ-T-391E
3.6
Performance.
When the endurance test is specified (see 6.2), the tires
Indoor
Endurance.
3.6.1
The
tires
shall
exhibit
no
evidence
of
shall be tested in l ccordance with 3.6.7.
c r a c k i n g , chipping,
chunking,
blowouts
open-tread
splice,
blister
or
other
visible
prior to removal from the wheel or base band and cut for inspection when tested
defects
Separation
Separation shall be allowable on one side only.
as specified in (3.6.2).
measured from the rim edge, l nd the combined
size shall not exceed l/4-inch in depth,
length
of
separations shall not exceed one-third of the circumference of the tire.
Hidden
Defects
Inspection.
After the endurance test has been completed, l
3.6.2
The
o f the tested tire shall be made for evidence of hidden defects.
visual
in-n
tire and wheel band shall be cut into not less than four equal cross sections, with each
section being cut circumferentially in mid-crown and on each side of the crown at the
point of maximum s h o u l d e r
thickness.
The cut sections shall then be inspected for evi-
dence of hidden defects such as gouges, porosity, splits, cracks, blisters, sharp or
pits, mold residue or otherwise not true or
burred
edges,
slivers,
splints,
lumps,
smooth.
For types I, II, and III tires, the load required to separate the
Adhesion.
3.6.3
tread from a base band or a wheel shall be not less than 60 pounds per inch of tire
The
rubber
separated
during
width at the base.
The area of adhesion shall be complete.
the
test shall show no l violence of blistering or porosity.
A
tension-testing
machine
or
apparatus
having
a
power-actuated
3.6.3.1 A p p a r a t u s .
clamp shall be used to apply and measure the force required to strip the tire from the
The clamp shall travel at a rate of 6 inches
metal wheel or rim to which it is adhered.
per minute.
The
machine
shall
be
provided
with
means
for
measuring
the
applied
tension.
Provision shall be made for mounting the tire and permitting it to rotate freely about a
fixed axis of rotation.
The tire shall be prepared for testing by cutting down to the
Procedure.
3.6.3.2
bonding surface of the metal wheel or base band and circumferentially along its edges on
The tire shall also be cut transversely down to the
both sides to minimize tearing.
metal base and separated circumferentially
a
sufficient
distance
to
permit
a firm
gripping of this free end of the tire by the power-actuated clamp.
The tire shall be
mounted
on
the
hub
and
spindle
assembly
and
positioned in such a manner that its axis of
rotation will remain parallel to the line of separation during testing and that the
applied force will be normal to the tangent of the wheel or rim at the line of separa-
With the free end of the tire gripped by the machine clamp, the machine shall be
tion.
started
and the tire stripped from the metal base.
If during the test the tire begins
to tear instead of separating wholly from the wheel, the machine shall be stopped and
the tire shall be cut with a knife to the metal base and the test started again.
Force
m e a s u r e m e n t s shall be recorded and the average force to separate the rubber from the rim
shall
be
determined.
A l t e r n a t i v e l y , the average force may be determined
from
an
integrating device attached to the testing machine which determines the area under the
force separation
curve.
The tire and the ambient air temperature, prior to and during
the tests, shall be between 70° and 110° F, with
the
actual
temperature r e c o r d e d .
The
tire shall have been conditioned at the
temperature r e c o r d e d .
The tire shall have been
c o n d i t i o n e d at t h i s
Temperature for a minimum of 16 hours prior to the test.
N o n c o n f o r m a n c e to
(3.6.3)
shall
constitute failure of this test.
3.6.4
Hardness.
The
tire
shall
be
subjected to the durometer hardness test specified
in Fed. Test Method Std. No.
601, methods 3021 and 3025.
Nonconformance
to
(3.2.1)
or
3.4(g), as a p p l i c a b l e , shall
constitute failure of this test.
T e n s i l e Strength and Elongation.
The tire shall be subjected to the tensile
3.6.5
strength and
elongation t e s t s
specified
Fed.
Test
Method
S t d . No. 601, methods 4111
and 6121, r e s p e c t i v e l y .
Nonconformance
to
(3.2.1)
shall
constitute failure of this test.
3.6.6
Aged
Tensile
Strength
and
Elongation.
The tire shall be subjected to the
aging
procedures specified in Fed. Test Method Std. No. 601, method 7221.
Nonconformance
to
(3.2.1)
shall
constitute failure of this test.
Indoor
Endurance
Test.
3.6.7
The sample tires
endurance tested
in
accor-
shall
be
dance with (3.6.1) on the apparatus described
in
(3.6.7.1).
nonconformance
to
(3.6.2)
shall constitute failure of this test.
7
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