The Washington times., 1920-07-17

TO procrastination which is inherent
to some degree In every human be-
ing. and (2) the inability OF any
laminated substance to resist disinte-
grafton when IL Is constantly nexed.
The second premise may require
eiucidation. Fabric tires are built
up OF layers OF cotton impregnated
with and cemented together by rub
ber. 30 long as sufficient air pres
sure 10 maintained in the tire to keep
IL hard under the weight OF the car
these layers, or piles. remain In prac-
tically nxed relation to each other.
When. however. the tire loses air to
such an extent that II nattens appre-
ciably on the ground the plies weave
back and forth. The energy developed
by the weaving motion of the tire
walls creates heat which disintegrates
the holding power of the fabric and
rubber. As there is more heat gen
Grated in this way than by contact
of the tire with the road surface, II
is a mistaken notion that tires should
be slightly Debated on a hot day TO
allow for heat expansion. The air In
properly inflated tires will expand
some what under the influence OF heat,
but the excess heat generated by
running on soft tires is harmful.
Another item in the list or evils
contingent upon underinfation, is the
damage likely to result when a soft
tire strikes a sharp stone or other
hard object in the road.
At the impact the tire. being insuf-
ficiently supported by the pressure OF
air within 1t, bends in and stretches
the inside ply to such an extent that
IL is weakened or actually broken.
This constitutes a bruise, and bruises
are the origin OF the most mysterious
blowouts. No mark Is left on the
tread, but the tire is damaged none
theless and IL is only matter OF time
before the fabric around the bruise
Is so weakened that 1t blows. Many
supposedly defective tires are re-
turned for adjustment because they
were damaged in this way by a large
stone or similar object.
The pressure in a tire should be
based on the load II carries. 1t Is OBJ
vious that a 30 by 3h-inch tire de-
signed to support a static load or o0O
pounds, will not stand up under dou-
BILE the load. Increasing the load
gives the same effect as decreasing
| the pressure. So, when you put seven
passengers in a three-passenger car
| you are overlooking the tires. In
! order not to damage them you really
ought to increase the pressure beyond
| that which the tires are normally sup
posed to carry. This is impractical,
30 the best the owner can do IL to
| avoid overlooking his car. The dam
| age to a casing is considerably in
creased when an already underin-
| hated tire is overloaded.
, All cars are not fitted with tires Of
| the right size; some are too small,
| some large enough. and others larger
than needed for Il given set Of condi'
tions. The largest tires can be op-
Grated considerably under the pres
sure specified and easier riding OBJ
tained. The tires that are just large
enough ought to be carefully watched
so the pressure always is kept to that
specified for the particular car and
size of tires. The small tires will
always give trouble.
Embossed on the side OF every tire
Is the imitation pressure for that tire
but not all makes indicate as well
the corresponding maximum static
load. This every owner should learn
! . Misalignment of the wheel is almost
as productive of tire troubles as un
lderinfation. No one would willingly
permit his car to be drawn sidewayi
along the road, because the abrasive
effect on the tires would be fatal IN
n snort time. Inlrty per cent OIL tn'
cars in service have masalienet
wheels, however, and the result o
dragging the tires ever so slightly a.
they rotate is almost as fatal. 1t Il
no uncommon occurrence for tires oil
wheels which are badly out of align
ment to be destroyed in only a few
hundred miles. Running in and ou
OF ruts. crossing railroad tracks a
speed, or humping into curbstone
may throw the wheels out Of line, an
the careful motorist will check then
frequently II he wishes to obtain full
service from his tires. Misalignmcnt
which are so slight as to be imper
ceptible to the eye may cause wear.
Examining tire treads closely WI
show whether or not the wheels ar
true A roughening of the rubbe
tread, appearing as though q file ha
been drawn across the surface. indi
Gates out of alignment Front wheel
can be checked for alignment quit
easily and quickly by any garagemai
| It involves simply the taking of mea,
urements between wheels at tho toI
at the bottom and at the front an