New-York tribune., 1917-07-15
Is There Any
Hot Weather
Tire Expansion?
Maker Says No; School
Principal, Yes-We
Vote in Negative

A bulletin from one of the tire COM
panies states: when you run your
tires underinfated in hot weather 70
combat air expansion, you require IN
creased bending Of the sides OF your
tires, and incidentally create more
heat-which is just the condition you
set about 70 avoid Soon the strength
of the cotton fibres is broken down and
you are treated to the unwelcomc
sound of the blowout.
"Whatever expansion occurs IN tire
while running is lost again after the
car has stood for short time and II
air has been removed from the tires
in the meantime they are then SUBJECT
to all the dangers of underinfiation.
Hundreds of tests have proved that
nc tire is in danger of blowing out be-
cause of hot weather expansion OF air
when tires are inflated to recommended
pressures. Motorists should refuse to
be misled by the hot weather theory
there is nothing in it worth mention
ing"
Opposed to this is a statement made
by the principal of New York auto
mobile school, who SAYS: Experienced
drivers know that in hot weather 1t is
not possible TO drive their cars with
50 high a pressure on the tires as they
have in winter. Considerable heat is
generated by rolling a tire over the
ground. This heat expands the air IN
the tire and increases the pressure.
In the winter this heat is absorbed TO
a large extent by the cold atmosphere
and the cold and wet pavements, and
therefore the pressure does not vary
so much. In the summer the roads
are very hot, the air temperature Is
high and the heat generated by frlc-
ton is not carried off to any appreci-
able extent.
"On trip last summer noticed
that the car was riding harder than
usual. and a test Of the pressure on the
tires developed the fact that it was
above normal. To find out just what
the difference in pressure was, we
tested it before leaving the garage
next morning. We found after rolling
about forty miles at an average speed
OF thirty miles an hour that the press
ure had increased about twelve pounds.
81 know that several of the tire
manufacturers instruct users not to
carry less pressure on the tires in hoo
weather, saying that the increased
pressure due 10 heat is not sufficient 10
materially affect their make. This is
probably true for new tires. or for
sbout two-thirds of their guaranteed
life. but if the tire has been weakened,
through having been run underlnfated,
or from fabric deterioration through
cuts in the tread, then | believe there
. danger from the increase in pressure
due to heat.
More tires are damaged by under
imitation than by overinfation. because
the former breaks down the side walls
through running fiat in practically
every case. Overinfaton causes
blowout only when the tire is weak at
some point. II would be good practice,
however, on hot summer days, to leave
the garage with the tire pressure about
ten pounds less than that specified by
the manufacturer as being correct for
his make. Any driver ought to test
out his tires after running at good
clip on a hot day and find out just
what they do. A little patience would
enable him to understand how much
his tires heat up and he could regulate
the pressure accordingly
II would be our opinion. in view of
some very definite tests made by tire
companies, to trail along with the mo
expansion" theory. Increasing twelve
pounds, even after going forty miles
AT an average Of thirty miles per hour.
Is lot of expansion. even if it means.
as 1T does. better than forty miles an
hour part of the time.
Our advice is don't uuderinnate and
dcnt drive fast. You'll get mileage
that way-summer or winter