The star-progress. (Opelousas, La.) 1917-1921, 1921-03-16
Air Under Pressure Perco'ates
Through Rubber Worn Tires Re-
quire Frequent Initiation

/ Among the various problems sun
mitteI TO tire manufacturers for sol
ution. the most common one appears
sure in a tube decrease although
to be the query-why does air pres
there is no leak?
A statement upon this interesting
point, recently prepared by the Lee
Tire & Rubber Co. of New York City.
explains many interesting character
istics of rubber together with sound
advice as to care OF tires.
while rubber is considered I'M
pervious to air, it is well-knoWn truth
that air will not remain forever, no
matter whether they are in road SER
vice or riding on the rear of the car.
Technically. air under pressure will
percolate through .-o52r, the degree
of percolation depcnGlg upon the
thickness Of the stock, the quality Of
the rubber, and possibly in no small
degree upon the backing. As an ex-
ample, rubber tube confined within
a glass smooth surface will lose less
air than one backed by rough or cor
rugated surface.
1T is because of this fact, also the
possibility Of small leaks, that tirh
manufacturers recommend weekly
pressure tests for the best results. II
is really proven that drivers who do
not make regular use of the pressure
gauge are often very badly fooled.
"Tires running on testing apparatus
are checked daily for pressure, and,
as a matter of information, we have
had tires run continually under heavy
load, at the rate Of twenty-five miles
per hour, for three days of twenty
four hours each, without showing any
pressure variation whatever. After
the third day a slight loss is usually
recorded each day. a maximum press
ure in these tests is five to eight
pound = i weeks time Of continuous
running. This variation. however,
we do not believe to be due 50 much
to the air escaping as to the casing
expanding as the tire wears down,
which goes TO show that tires after
beginning to show wear need inflat-
ton oftener than new ones and should
be tested Cftener for initiation pressure
if maximum mileage is to be obtained.
considerable attention and study
has been given to the subject of in
flation pressures in recent years be-
cause it has been necessary to dis
card many tires before they were
worn out because of underinfIation.
The pressure formerly recommended
for the various sizes of tires were
maximum pressures for maximum
loaCs, but in recent years a new SEIZED
ule Of pressuTes has been worked
out On a scientific basis, by consider
ing the weight Of the car, the load
carried, and the type of car used,
whether fabric, ord or puncture-
proof and the pressures recommend
ed at present vary according to the
requirements and represents the min
imum, instead of the maximum as
formerely, and must be maintained to
obtain the greatest mileage.
a perfectly inflated tire will re-
sist the impact of bruise more read
lily. 1t is the quick bending action
that causes rupture to the tire and
the less resistance there is, the quick
er it will break. For this reason
we believe, that the success of a we'll
placed repair depends on the infla-
ton being kept up, as a jar at the end
OF repair is thereby eliminated. On
underinflated tires the end OF a re-
pair receives a kick on every revolu-
ton and gradually loosens and blows
out the job. A large percentage of
repairs which fail are due to tAis
cause, as the repaired section is
stronger and SITTER than the rest Of
the tire and naturally resfsts the bend.
Tread patches are loosened in the
same manner and spices are opened
up. Repairmen should advise car
ore md drivers that, due to th2sa
conditions. air pressure shauld be
key; up"