S ec. 10
P age 60
WHEELS A N D TIRES
Figure 7— D a m a g e d or Sp rung Rings
E rosion and chipping of bead seat of lock ring,
resu ltin g from e x c e s s iv e co rro sio n .
NOTE: Insure that rep lacem en ts are made
w ith the proper s iz e s and types of rim s and rings.
W heel M aintenance
Thoroughly rem ove ru st, dirt, and other fo r
eign m a teria ls from a ll su r fa c e s. Hand or ele ctric
w ire b r u sh es, sand b lastin g or chem ical baths may
be u sed . Gutter of rim b a se should be cleared of
rust and other m a ter ia ls obstructing sa fe, p ositive
sea tin g of rin gs.
Figure 9 — Inflation of Tires
Bead se a t a r e a s of rim should be fr e e of rust
and rubber d ep o sits. T his is e sp e c ia lly im portant
for d rop -cen ter tu b e le ss r im s, b eca u se the 15°
bead sea t is the a ir -s e a lin g elem en t.
R ings should be clean ed with w ire brush. Pay
p a rticu la r attention to sea tin g su r fa c e s and bead
se a t a r e a s.
Paint rim by brush or spray with a fa st-d ry in g
m etal p r im e r . S u rfaces should be clean and dry
p rio r to painting. Insure that bare m etal a r e a s on
ou tsid e or tir e sid e of rim are covered . T his i s
e sp e c ia lly im portant on d rop -cen ter tu b e le ss rin gs,
b eca u se w arm and so m e tim e s m oist a ir is in con
stant contact with the m etal su rface on the tir e
sid e of the rim .
INFLATION OF TIRES
(R efer to F igu re 9)
Inflate to c o r r e ct p r e s s u r e when tir e s a re co o l.
If tir e s are continually carryin g l e s s than the r e c
om m ended m axim um load, adjust air p r e ssu r e
downward to corresp on d to the actual load carried .
N ever "bleed" tir e s to r e lie v e build-up of
p r e s s u r e . T ire tem perature w ill in c r e a se when the
tir e is in s e r v ic e and allow s for the norm al build
up in a ir p r e s s u r e . T ire tem perature and a ir p r e s
su r e w ill rem ain within lim its that are not harmful
to the tir e when u sed in accord an ce with the r e c
om m endations for load and a ir p r e ssu r e .
If e x c e s s iv e build-up of a ir p r e s s u r e o c c u r s,
load, underinflation, sp eed , or a com bination of
th e se is resp o n sib le. U se the s iz e and type of tir e
that has the capacity to ca rry the load at re c o m
mended cold starting p r e s s u r e .
TIRES
OVERLOAD
O verloading is the ca u se of many kinds of cord
body breaks and is the m ost co stly of a ll truck tir e
a b u se s. Such b reaks are due to abnormal flexin g or
overw orking of the cord body of the tir e .
O verload fle x b reaks occur in the sid ew a ll or
in the shoulder of a tir e and run with the c ir c u m
fer e n c e of the tir e . S o m etim es they are only two
o r th ree in ch es long.
Other tim e s they w ill extend partly around the
tir e , resu ltin g either in a la r g e blowout or a pinch
ed tube which allow s the t ir e to go flat.
N orm al flexing of a tir e can go on indefinitely
without causing any ap preciable damage to the co rd s.
But if the tir e is overw orked or overflexed from
overload , abnorm al heat is gen erated and the cords
b ecom e fatigued and break.
Underinflation w ill ca u se th is sa m e r e su lt. In
addition, crow ned roads, sprung a x le s, m ism atched
duals and poor load distribution tend to produce
fle x breaks; how ever, overloading ex ceed s a ll other
