Pueblo chieftain., 1921-03-13
AIR PRESSURE
WILL PERC0LATE
THRU RUBBER
Reason That Tire Men
Recommend
Tests !

Among the various problems submit
ted to tire manufacturers for solution.
the most common one appears to be
the query-why does air pressure in
a tube decrease although thcre Is no
leak?
A statement upon this interesting
point recently prepared by tho Lee
Tire and Rubber Company of Nov
York City explains many interesting
characteristics of rubber together With
sound advice as to caro- of tires.
While rubber is considered impef-
vious to air. it is a well-known truth
that air will not remain in tires for
ever, no matter whether they are in
road service or riding on the rear Of
tho car. Technically. air under pres
sure will pcrcolato thru rubber, the d.
gree of percolation depending upon the
thickness of the stock. the quality OF
the rubber, and possibly in no small
degree upon the backing. As an e1-
a glass smooth surface will lose less
air than one backed by a rough or cor
rugated surface.
1T is because Of this fact, also tho
possibility OF small leaks. that tirs
manufacturers recommend weekly
pressure tests for best results. 1t @
really proven that drivers who do
not mako regular use of pressure
gauge are often very badly fooled.
Tires running on testing appara-
tus are checked daily for pressure.
and as n matter of information, we
der heavy load, at the rate OF twenty
five miles >er hour. for thrce DAYS OF
twenty four hours each, without show
| ing any pressure variation whatever.
After tho third day a slight loss Is
usually recorded each day. A maxi
mum pressure variation in these tests
is five to eight pounds in a weeks
| time of continuous running. This
variation, however, wc do not believe
| TO be due so much to the air escaping
as to the casing expanding as the tho
wears down, which goes to show that
| tires after beginning to show wear
need initiation oftencr than new ones
and should be tested oftener for fnfla-
tion pressure it maximum mileage II
to be obtained
Considerable attention and study
has been given to the subject OF inf1a-
ton prcssures in recent years because
IL has been necessary to discard many
tires before they werc worn out be-
cause of under-inhati ton. Tho pres
rures formerly recommended for tho
various sizes of tires were maximum
prcssurcs for maximum loads. but in
recent years a new schedule OF pres
surcs has been worked out on 4 scien-
tific basis, by considering the weight
of tho car, the load carried, and tho
type OF tire used. whether fabric, cord
or puncturc proof and tho prcssurcs
recommended at present vary accord
ing to tho requirements and represents
tho minimum, instead of the maximum
as formerly, and must be maintained
TO obtain the greatest mileage.
"a perfectly inflated tire will resfrt
the impact OF a bruisc more readily.
II is tho quick bending action that
causes rupture to the tirc and the less
air resistance there is, the quicker IL
will break. For this reason, We be
lcvc that tho success OF we'll placed
repair depends on tho initiation being
kept up. as jar at tho end OF a repair
Is thereby eliminated. On nndertnflat-
cd tires tho end of a repair receives 4
kick on every revolution and SrAdu-
ally looscns and blows ont the toh. A
large percentage OF repairs which fau